Nutritional and therapeutic perspectives of Stevia rebaudiana as emerging sweetener; a way forward for sweetener industry

ABSTRACT

In recent years, new avenue has been opened for extensive research and debate between Natural and artificial sweeteners. Stevia rebaudiana has emerged as a potent and remarkable substitute to artificial and calorie dense sweeteners. Stevia being natural and zero caloric is becoming a choice of many diet conscious people. The leaves and extract of Stevia plant are used to sweeten different food stuffs, desserts, beverages, etc. across globe especially in USA, Europe, China and Japan. Sweet components responsible for intense sweetness are the Steviosides having sweetness ranging from 250 to 400 times sweeter as compared to sucrose. Bioactive moieties in Stevia play vital role in health promotion aiding and boosting immune system to fight against cancer, cardiovascular diseases, diabetes and lower the occurrence of various other ailments diseases. This review article encompasses the biochemical, nutritional, therapeutic potential and end use applications of Stevia.

RESUMEN

En los últimos años se ha abierto una nueva vía que propicia una extensa investigación y debate sobre las cualidades de los edulcorantes naturales y artificiales. La Stevia rebaudiana se ha convertido en un sustituto pujante y notable de los edulcorantes artificiales y de aquellos densos en calorías. Tratándose de un producto natural sin calorías, la stevia se está volviendo una opción para muchas personas que han tomado conciencia de su dieta. Las hojas y el extracto de la planta de stevia se usan para endulzar diferentes alimentos, postres, bebidas, etcétera en todo el mundo, especialmente en EE. UU., Europa, China y Japón. Los componentes responsables de su dulzura son los esteviósidos, cuya dulzura es entre 250 y 400 veces más intensa que la de la sacarosa. Por otra parte, los componentes bioactivos de la stevia desempeñan un papel vital en la promoción de la salud, ayudando y estimulando el sistema inmunológico para luchar contra el cáncer, las enfermedades cardiovasculares, la diabetes y reducir la aparición de otras enfermedades. El presente artículo de revisión aborda el potencial bioquímico, nutricional, terapéutico, así como las aplicaciones de uso final de la stevia.

KEYWORDS:

• Stevia
• biochemical characterization
• functional attributes
• Stevioside metabolism
• therapeutic remuneration
• end user application

PALABRAS CLAVE:

• Stevia
• Caracterización bioquímica
• atributos funcionales
• metabolismo de esteviósidos
• remuneración terapéutica
• aplicación para el usuario final

1. Introduction

A long time ago, our ancestors were more concern about their health and diet as compared to us. It was something normal when they ate many types of herbs as supplements to maintain their health status and used to prepare different medicines and tonics on the basis of their experiences. Therefore people were more healthy and protected from certain ailments (Halim, Sarijan, & Shaha, 2013). Now a day’s obesity and overweight are the root causes of wide number of health complications; diabetes being the major one, followed by pulmonary and renal problems, hypertension, pregnancy complications, surgical risks, hyperlipidemia, cardiovascular diseases, etc. Regular consumption of food stuffs rich in calories especially sucrose sweetened snacks and beverages leads to above mentioned metabolic disorders. In modern era, people are always busy in their daily activities and pay much less attention towards the quality of their health. An increased demand of various supplements and additives has been observed to fulfill the nutritional deficiencies of masses which depicts their irregular dietary patterns (Carocho, Morales, & Ferreira, 2015). People also try to justify their dietary needs by preferring to eat junk foods, calorie dense sweetened food items that not only provide energy to them but disturb their metabolic balance as well (Abou-Arab, Abou-Arab, & Abu-Salem, 2010). Quite a number of intense sweeteners either natural or artificial, mild or intense, nutritive or non-nutritive are used by people and food industry on daily basis (Geuns, Buyse, Vankeirsbilck, & Temme, 2007). Some of the artificial sweetener such as aspartame, saccharin, acesulfame-K, neotame and sucralose with their extensive utilization leads to fatal maladies like cancer, phenylketonuria, etc. (Liu, Li, & Tang, 2010; Zygler, Wasik, & Namieśnik, 2009).

Sweeteners provide pleasing sensations with or without calories and as food additives; their main function is to enhance the product taste and quality. Nutritive sweeteners being natural used to provide calories and mainly include fructose, glucose, sucrose, honey and sugar beet. They have been given the status of Generally Recognized as Safe status (GRAS) by US Food and Drug Administration (FDA) to these natural sources. But there exist certain health-related problems that are associated with the over consumption of nutritive sweeteners. Intense sweeteners are either natural or synthetic compounds or their derivatives and metabolites. Artificial sweeteners are prepared in laboratory, having taste similar to sucrose, fructose and glucose and provide no or minimal calorie intake. Mostly high intensity sweeteners are used in minute amount as they are 50–100 times sweeter than sucrose (Journal of the American Dietetic Association, 2004). Saccharine is very harmful for normal physiological functioning of body causing digestive and metabolic issues when consumed on daily basis (Cleave, 2013).

Stevia (Stevia rebaudiana) is indigenous to Brazil and Paraguay and known before recorded history. Stevia is a genus of appropriately 200 species of perennial herbs and shrubs that belongs to the sunflower family (Asteraceae). The plant can attains the height up to 1 m or may be more in a wide range of soil with consistent supply of moisture and suitable drainage system (Lemus-Mondaca, Vega-Gálvez, Zura-Bravo, & Ah-Hen, 2012). With the passage of time, it became famous globally. Based upon sweetness of its leaves, it is known with different names viz. honey leaf, Candy leaf, sweet herb and sweet leaf of Paraguay. SGs/Steviosides were extracted from Stevia by two French chemists in 1931 (Carakostas, Curry, Boileau, & Brusick, 2008). In 1964 and 1968, Stevia was commercially cultivated in Paraguay and Japan, respectively, and used extensively by chewing gums, breads and pickle manufacturers. Since 1970s, with the development of extraction followed by refining and decolorization the commercial profiteering of Stevia became more common in Japan (Huang, Tian, Pei, Liu, & Di, 2018). Early Stevia formulations had depicted quite evident licorice aftertaste that hindered its industrial utilization particularly in beverages. Sucrose provide 4 kcal/g energy and used as standard for sweetness level measurement of others sweeteners Aspartame is 200 times sweeter than sucrose, neotame has 700–1300 times more sweetness, saccharine has 300–500 times sweetness, sucralose is 600 times sweeter while acesulfame-K has sweetness level of 200 times than sucrose with no calories (Barroso et al., 2016; Savita, Sheela, Sunanda, Shankar, & Ramakrishna, 2004a). However, the sweetness level of Stevia ranges from 250 to 300 times higher as compared to sucrose with high-melting point and low-water solubility (Goyal, Samsher, & Goyal, 2010).

2. Global regularity status of Stevia

Previously, there has been great debate on giving approval to Stevia as mainstream sweetener. There are different schools of thoughts having varied views and reservation regarding regulatory status of Stevia. Sweeteners industry is based on various stakeholders that have their own pertinent benefits of prime interest. It took a long time and episodes of debates by different international governing organization that on the basis of research outcomes given the GRAS status and acceptable daily intake (ADI) be given to Stevia. A brief history of such struggle is reviewed as under.

The utilization of steviol glycosides (SGs) is now encouraged as food additive in order to minimize the dependence of masses on calorie rich sugar like from sugarcane, beet sugar, honey, etc. that would ultimately lessen the incidence of diabetes and its allied diseases (Romo-Romo et al., 2017). European Union (EU) regulated scientific committee on food additives have reviewed the safety status of Stevia and related products and declared that further research is needed to support the safety status of Stevia (Gibson et al., 2017). Several petitions remained unattended at the European Food Safety Agency (EFSA) regarding Stevia extracts (Additives et al., 2018a). At that time Stevia powder and extract remained restricted to few countries including Brazil, China, Korea, Japan, Paraguay, Thailand and Israel. During 1990s, on several occasions, FDA had raised different observations and asked food manufacturers to provide the regulatory status of their products that have Stevia as ingredient which is not sanctioned under Dietary Supplement Health and Education Act. During that time, FDA has also raised some points regarding the utilization of Stevia products due to lack of safety certification that are thought to affect the various metabolic functions especially glycemic level and fertility system. In 1994, Dietary supplement health and education act (DSHEA) was approved by USA that has allowed to utilize extracts from Stevia leaves in different supplements (Additives et al., 2018b). As well as in 1995, FDA has also revised the restrictions and approved Stevia as dietary supplement. In 2011, EU has declared Europe and North America not to utilize Stevia as food additive as it is banned by FDA (Elzinga et al., 2017). During the 58th, 63rd and 68th meetings of Joint Expert Committee of FAO/WHO on food additives (JECFA) reconsidered the SGs safety limits. Steviol glycosides are converted to steviol equivalents to compare their daily intake and safety limit. To convert stevioside and rebaudioside A to steviol equivalents the stevioside quantities are multiplied by factor 0.40 and rebaudioside A quantities are multiplied by 0.33. It was declared that temporary ADI such as 0–2 mg/kg body weight/day is in correspondence with 0–6 mg of rebaudioside A/kg body weight/day using this molecular weight conversion. However, the permanent ADI for rebaudioside A is 0–12 mg/kg body weight/day based on an anticipated permanent ADI for steviol equivalents of 0–4 mg/kg body weight/day (Carakostas, et al., 2008). In addition to detailed specifications information, JECFA had asked to conduct various human studies to find out the blood pressure and blood glucose lowering effect of Stevia thereby maintaining the insulin level in body for glucose homeostasis. JECFA, after reviewing the submitted information stated to lessen the safety factor up to 100 as permanent ADI. However, in 68th meeting of JECFA, data provided were not sufficient to meet the committee requirements regarding the potential impacts on blood glucose and blood pressure homeostasis. In 2010, European Food Safety Authority (EFSA) evaluated and sum up Stevia’s safe attributes and finally set 4 mg/kg body weight/day as the Acceptable Daily Intake (ADI) (Logue, Peters, Gallagher, & Verhagen, 2015; Urban, Carakostas, & Brusick, 2013).

In the 69th meeting of JECFA, 4 mg/kg bw ADI was established for SGs and NOAEL (no observed adverse effect level) status was conferred to Stevia for its usage at commercial and domestic level (Purkayastha et al., 2016). JECFA have taken into consideration to give the status of sweeteners to Stevia integral components which were Stevioside, Rubusoside, Dulcoside A, Steviolbioside and Reb. A-F. While Stevioside and Rebaudioside A are the prime sweetening agents due to their high level of sweetness and concentration. United Nations have devised the committee from its member nations for Codex Alimentarius Commission (CAC) standards in order to establish their own country level standards for Stevia. In 2011, the CAC came up with a draft determining the maximum SGs level in food stuffs (Purkayastha et al., 2016). According to the EU regulation No. 1131/2011 from European Union SGs are now permitted to be used as sweetening agent across Europe. EU established a criterion in which commercially available sweetener should have at least 95% of Steviol glycoside content in it with 75% of Stevioside and total Rebaudioside A (Abdel-Rahman et al., 2011; Purkayastha et al., 2016).

3. Stevia cultivation

Consumers increasingly demand products from natural sources. This is the driving force for stipulation of stevia by food industry. Globally more than hundred-thousand-hectare area is under Stevia cultivation, in Japan almost 2–3 billion dollar/year is the total market value, moreover China is extensively doing Stevia cultivation. The average height of this short-day plant is up to 1 m at which elliptical leaves are arranged in alternate arrangement pattern with 2–3 cm length. The plant is grown best at semi humid sub-tropical environmental adaptation of 200–400 m above sea level with average rainfall of 1500–1800 mm and temperature variation of 16–40°C. In Asia, the very first commercial crop of Stevia was cultivated by Japan in 1968 having extensive root system with pale purple throat of white flower and brittle stem system at which leaves are arranged in small corymbs (Ranjan, Jaiswal, & Jena, 2011).

Normally, Stevia is cultivated in March-April and June-July months in different parts of world, harvesting is done after 75–90 days (Ulbricht et al., 2010). Crude extract and steviosides content of Stevia increases when pH of soil decreased that ultimately enhance the sweetness level of Stevia (Das, Gantait, & Mandal, 2011). The best growth of Stevia is attained at 20–24°C with soil pH 4–6 (Kobus-Moryson & Gramza-Michałowska, 2015). Single plant of Stevia can be used for more than 8 years and provide healthy green leaves for usage. Dry weight of Stevia may be from 15 to 35 g per plant. Tissue culture technique has also been extensively employed to cultivate Stevia in different soils and regions (Sharma et al., 2015). In recent times, in vitro culture and micro propagation is the best method to tackle the problems of output and get the ample amount of stevia crop in best possible short time. (Uddin et al., 2006) have performed in vitro propagation by using leaves, nodal and inter-nodal segments of Stevia. Multiple shoots were obtained from nodal explants and proved it to be the best method for large scale Stevia production (Barroso et al., 2016).

4. Structural expression of Steviosides

In 1931, Bridel and Lavieile have started working on the structural, stereochemistry, biochemical and analytical characterization of SGs of Stevia which are refined with advancement and sophistication of instruments (Puri, Sharma, & Tiwari, 2011). Stevia has gone through different chemical and enzymatic reactions in order to get more than 100 different natural components which are SGs or Steviosides. Structurally, Steviol glycoside 13oxy kaur-16-en-19-oic-acid ß-D glucopyranosyl ester) is a glycoside with residues attached to Steviol aglycone, possessing cyclopentanon-hydrophenanthrene skeleton. All different screened glycosides primarily differ in amount mono, di and trisaccharide carbohydrate residues (R1 and R2), at positions C13 and C19 but share the same backbone of Steviol (Lemus-Mondaca et al., 2012).

The major Steviol glycoside which is Stevioside has been altered by different chemical and enzymatic operations into another major Steviol glycoside named as Rebaudioside A. Methanolic extraction of Stevia leaves leads to the isolation Rebaudiosides B. However, Rebaudioside C, D and E were obtained by the further fractionation of Stevia leaves extracts. Alkaline hydrolysis of both Rebaudioside A and D separately can provide Rebaudioside B which inferred that these Rebaudiosides are esters of each other. In the same ways, scientists have revealed that Rebaudioside C share the same structure as that of Dulcoside A and B (Wu et al., 2012). Steviosides as well as different Rebaudiosides were also prepared synthetically from Steviol by its transformation using different chemicals as well enzymes (Gasmalla, Yang, Amadou, & Hua, 2014). With the increase in number of bounded sugar units with Steviol aglycone, sweetness level enhanced (Kovylyaeva et al., 2007). However, SGs differ in the sweetening or edulcorant properties from each other. Significant metallic or bitter aftertaste is observed from pure SGs (de Oliveira et al., 2011). Naturally, the sweetness level of different Stevia constituent is generally greater than sucrose, which is considered as the scale with 100 as it sweetness value. The sweetness of different steviosides is as: Rebaudioside A, B, C, D and E are 250–450, 300–350, 50–120, 250–450 and 150–300 times sweeter, while Dulcoside A and Steviolbioside are 50–120 and 100–125 times sweeter than sucrose. Therefore, the sweetness level of Stevia ranges from 250 to 300 times higher as compared to sucrose with high melting point and low water solubility (Goyal et al., 2010). The major Steviosides concentration are reported as Stevioside (4–13% w/w), Dulcoside A (0.7%), Rebaudioside A (4%) and Rebaudioside C (2%) (Gupta, Sharma, & Saxena, 2016). Rebaudioside A is the sweetest, most stable and less bitter than other steviosides. It has also been reported that synthetic sweeteners like aspartame, cyclamate, neotame, etc. are less stable as compared to Stevioside (Rajasekaran, Ramakrishna, Udaya Sankar, Giridhar, & Ravishankar, 2008).

5. Chemical composition of Stevia

5.1. Proximate composition of Stevia

Stevia rebaudiana is famous for its sweetening properties but there are many other aspects for its popularity and getting importance for being the rich source of nutritional and functional components like protein, fiber, minerals, vitamins, phenolic acids, free radical scavenging and antioxidant capability, nutraceutical properties, etc. A number of scientists have worked on different aspects and properties of Stevia and found some remarkable results. Fresh Stevia leaves contain almost 80% moisture and provide 270 kcal/100 g energy (Savita et al., 2004a). In dried leaves, the moisture content is usually influenced by extent and method of drying. In order to avoid deterioration, it is recommended to dry these leaves by sun or oven drying methods. Post-harvest drying of Stevia leaves for almost 8 h is necessary that will concentrate the sweet glycoside components in leaves (Samsudin & Aziz, 2013). Gasmalla et al. (2014) determined that Stevia has considerable amount of protein and can absorb sufficient water in product development. Protein content in Stevia leaves was recorded as 6.2–20.42% (Gibson et al., 2017).

Fat content in extraction from Stevia was found to be only as 4.34% that is not high enough comparing to other oil sources however fatty acid composition of Stevia presents it as a good source for optimum growth. Gasmalla et al. (2014) determined that Stevia leaves have 6.13 ± 0.63% fat content. Fibers are chemically polysaccharides, oligosaccharides, lignins and their associated plant components. Fiber are resistant starches which remained undigested during metabolism of carbohydrates, therefore escape absorption in small intestine of humans. Regular utilization of dietary fiber in food provides health benefits like promotes normal functioning of digestion, reduces constipation, maintains body weight, removes extra cholesterol content and save body from cardiovascular disorders by regulating normal blood pressure. It also helps in prevention of cancer by providing a surface for attachment to colonic bacteria and also ease the transition of food via intestines (Sánchez-Muniz, 2012; Takasaki et al., 2009). Stevia is source of ample amount of dietary fibers and it has been reported that 18 g/100 g crude fiber is present in Stevia leaves powder while (Gasmalla et al., 2014) reported crude fiber in Stevia as 13.56–18.5%.

Chemical constituents of Stevia was determined by Savita et al. (2004b) declaring moisture content, calorific values, protein content, fat content, ash content and crude fiber as 4.45–10.73%, 362.3–384.2 kcal/100 g, 12.44–13.68%, 4.18–6.13%, 4.65–12.06% and 4.35–5.26%, respectively. According to the research findings of Segura-Campos et al. (2014) on Stevia, they found it to be a good source of crude protein (12.11–15.05%), carbohydrates (64.06–67.98%) and crude fiber (5.92–9.52%). However, 28.61–29.12 g/100 g of total dietary fiber content was found in which major share was of insoluble dietary fiber that ranges in 87.79–70.02%. Acid detergent lignin (2.28–8.98%), neutral detergent fiber (18.11–19.29%) and acid detergent fiber (14.16–17.77%) have been found in impressive amount. Hemicellulose and cellulose were 1.51–3.96% and 8.79–11.78%, respectively (Sánchez-Muniz, 2012).

5.2. Mineral composition of Stevia

Minerals are diet components inevitable for the up keeping of life and good health. Metabolic processes need them for proper functioning, some are required in major quantity while other in minor or trace amount. Major elements that are required include magnesium, potassium, chlorine, sodium, phosphorous, sulfur, calcium is classified as macronutrients. However, micronutrients include iron, cobalt, zinc, copper, selenium, iodine, molybdenum, chromium, manganese, etc. Stevia leaves have good mineral profile with nutritionally essential elements in reasonable amount i.e. calcium, potassium, magnesium, iron, copper, manganese, zinc and sodium in fresh as well as dried leaves. Potassium, important mineral present in high amount followed by calcium, sodium and magnesium being beneficial for human health as reported by many authors (Lemus-Mondaca et al., 2012). Potassium works as an enzyme activator which is vital in making different peptide bonds. Stevia has sufficient amount of zinc (1.42 mg/Kg) which is the structural as well functional part of different enzymes like transphosphorylase, peptidases, etc. which plays an important role as anti-bacterial, anti-fungal, antiviral and anticancer element. It is also an integral part of both DNA and RNA polymerase (Brisibe et al., 2009). Iron is the integral part of hemoglobin and works to transport oxygen across the body for continuation of body process. Therefore, diets missing in iron will lead to several body disorders major one being anemia. It is a component of myoglobin protein found in muscle. Bone mineralization, enzymatic action, proper functioning of nervous system is regulated by magnesium concentration in body. Calcium is an integral part of teeth and bones performing vital role in normal muscle contraction. Stevia emerged as a pronounced source of potent minerals thereby playing a protecting role against diet disorders. It balances and conserve different metabolic processes (Khiraoui et al., 2017).

Metabolic processes need them for proper functioning; some are required in major quantity while other in minor or trace amount. Major elements that are required include magnesium, potassium, chlorine, sodium, phosphorous, sulfur, calcium is classified as macronutrients. However, micronutrients include iron, cobalt, zinc, copper, selenium, iodine, molybdenum, manganese, etc. (Kesler & Simon, 2015). Trace mineral elements are needed for normal physiological functioning of metabolic processes. Despite of this, metal elements which are present in earth’s crust in excess amount have no role in normal functioning of metabolic working but hinders or inhibits them as well. Heavy metals with key health concern include lead, cadmium, mercury and arsenic. These metals may accumulate in the tissues of biological systems causing toxic issues in human system natural functioning. Subsequently, the toxic effects that occurred are collectively termed as bioaccumulation (Li, Ma, van der Kuijp, Yuan, & Huang, 2014). In the process of bioaccumulation, the heavy metals may accumulate in human body via food such as from food of animal origin like fish, beef, mutton, animal oil, etc. the results of this toxicity falls from subtle to serious disease symptoms (Roohani, Hurrell, Kelishadi, & Schulin, 2013). These metals may absorb in human body for long exposure time and affect the body by delaying and stopping metabolic processes leading to irreversible serious health distortive ailments (Järup, 2003). By removing these toxic heavy metals and their components from the human body can prevent crucial effects but the removal is much difficult as it looks, so the only best possible way to avoid is awareness and adopting safe and healthy measures.

5.3. Fatty acid profile of Stevia

Lipids are richest energy reserves providing 37 kJ/g of energy on complete digestion thereby providing sustainable energy for continuation of normal body function. In this regard, ingestion of fat soluble vitamins A, D, E and K are of prime importance in health sustenance. Chemical composition of triglycerides depicts that it constitutes one unit of glycerol bounded with three same or different fatty acids that eventually changes the chemical nature of fatty acids. Similarly, saturated or unsaturated fatty acids occur in different proportions in food furnishing body with nutritional and medicinal benefits. Polyunsaturated fatty acids (PUFAs) have two major classes that are omega-3 and omega-6 fatty acids. Alpha-linolenic acid, linoleic acid eicosapentaenoic acid and docosahexaenoic acid are the essential fatty acids as human body cannot prepare them and we must need these from diet. These essential fatty acids are interconvertible in a limited amount with less than 15% conversion by liver action. Thereby, only way to maintain the level of these essential fatty acids is to have them from dietary supplements and varied food sources (Jones & Papamandjaris, 2001; Onal, Kutlu, Gozuacik, & Emre, 2017).

Fatty acid profile of food components is commonly determined by using gas chromatography. It is used to change over a composite mixture into volatile compounds. Essential standard of gas chromatography is a specimen which goes through heated column in which sample is vaporized at elevated temperature, programmed as per protocol followed. (Shukla, Mehta, Bajpai, & Shukla, 2009) have found the concentrations of palmitoleic acid, stearic acid, linolenic acid, palmitic acid and oleic acid as 1.27 g/100 g, 21.59 g/100 g, 1.18 g/100 g and 12.40 g and 4.36 g per 100 g fat, respectively. Tadhani and Subhash (2006) identified various fatty acids primarily stearic, linoleic, linolenic, oleic, palmitic and palmitoleic acids as 1.18, 27.51, 1.27, 4.69, 12.40 and 21.59 g per 100 g fat, respectively. Siddique, Rahman and Hossain (2016) analyzed the hexane extract of Stevia rebaudiana from hexane and determined free and bound fatty acids. They found that relative percentage of palmitic acid in extract was highest as compared to others fatty acids and it was the 86.50%.

5.4. Functional properties of Stevia

Functional properties are the characteristic of a food which specifies quality, structure and nutritional value of a product. These are determined by organoleptic and physicochemical attributes of a food e.g. pH, fat absorption capacity, water absorption capacity, bulk density, swelling index, etc. pH is a measure of hydrogen ion concentration; measuring acidity or alkalinity. pH of stevia powder dissolved in deionized water was found to be 6.1 which is slightly acidic and close to neutral showing that hydrogen ions concentration is less than hydronium ion (H₃O⁺) concentration.

Powders, granules and other finely divided solid materials contain a property called bulk density which is specially used regarding food stuff, food ingredients or any other matter of corpuscular or particle nature materials. Stevia leaves powder appears to have less bulk density. In the design of food products which are high in protein or fiber, it is important for their various properties to control how much water is held by the food material. This water-holding capacity (WHC) relates to many sensory, health and nutritional properties. Thermal processing of protein-rich food is accompanied by a loss of water (containing various nutritional components), so better control of water means reducing loss of the nutritional value. WHC is directly associated with the rehydration and Stevia appears to have good WHC. High protein level can be a possible reason for enhanced WHC.

Swelling power is the property of thick or viscous food items like gravies, soups, doughs, etc. due to vital role of proteins. On the other hand, proteins have a very good ability to stabilize emulsion which is crucial in product preparation like cakes, frozen desserts, coffee, batter, milk whiteners, etc. But the composition and processing conditions to which the product is subjected, affect the emulsion property. Fat absorption capacity can also be termed as physical binding/absorption of oil. Stevia leaves powder is considered to have good fat absorption capacity thus making it an efficient commodity in food processing. Fat enhances the effect of flavor retainers and improves mouth feel of foods. Estimated fat absorption capacity of Stevia leaves powder is 4.5 mL/g.

Functional properties of Stevia leaves powder have been reported as 0.443 g/mL bulk density, 4.7 mL/g WHC, 4.5 mL/g fat absorption capacity, 5.0 mL/g emulsification value, 5.01 g/L swelling index, solubility was 0.365 g/L and pH was 5.95 (Segura-Campos et al., 2014). Lemus-Mondaca et al. (2012) and Rao (2014) calculated the Stevia powder bulk density as 0.443 g/mL. WHC was found to be 4.7 mL g/L, while fat absorption capacity calculated to be 4.5 mL g/L and emulsification value of Stevia powder recorded as 5.0 mL g/L. Swelling index of Stevia leaves powder was reported as 5.01 g g/L, solubility was 0.365 g g/L and pH was 5.95. Savita et al. (2004a) evaluated that protein help to develop and maintain the emulsions. Development and maintenance of emulsions in various food products is very necessary to achieve and maintain the desired attributes of the food products such as batter, coffee, cakes, frozen desserts, milks and whiteners (Nehir El & Simsek, 2012).

6. Metabolism of Steviosides

The sweetening moieties of Stevia with backbone of Steviol including Stevioside and rebaudioside A are the major contributors in sweetness. These SGs play an important role in body metabolism as they only provide sweetness without any increment in body calories. Microbiotas of gut hydrolyze these SGs into diterpenoid aglycone known as Steviol and are not further metabolized by the body therefore absorbed in blood stream from intestine for removal after filtration at kidneys. According to Koyama et al. (2003) and Muanda, Soulimani, Diop and Dicko (2011) who worked on the human digestive tract in relation to Steviol metabolism deduced that Steviol remained unaltered either at high or low concentrations. The study also explained that role of liver in glucuronation of SGs in which these are absorbed and clear from blood stream. Liver transferred the glucornated molecules of Steviol to kidneys for filtration into urine. However, very small amount of these glucuronidate are not filtered and remained in colon are excreted via feces. Rebaudioside A has lower hydrolysis rate as compared to Stevioside. A recent mass spectrometry study has declared that Steviolepoxide is not a microbial metabolite of SGs. Hydrolysis of glucose components is done by certain bacteria species that utilize their β-glucosidase activity which specifically hydrolyze polymerized glycoside chains. Similar results have been recorded by different studies conducted on human and animal mixed fecal flora incubation which indicates that rats are pertinent models for bio efficacy studies on SGs (Kujur et al., 2010). Yadav and Guleria (2012) have found similarity in their study on the microbial metabolism of rebaudioside A and Stevioside which form single hydrolysable product known as Steviol that ultimately absorbed from the intestinal tract.

Renwick and Tarka (2008) did an in vitro study on degradation of Steviosides and rebaudioside A by using rat intestinal microbiota into diterpenoid aglycone. The degradation of these Steviosides into Steviol requires different time such that complete steviosides to Steviol conversion requires only 2 days when incubated in whole cell suspension, 6 days are need for Rebaudioside A transformation under similar conditions. The metabolic fate of rats and humans is predicted to be similar and it was confirmed from micro flora studying of rat caecum and lower human bowel qualitatively as well as quantitatively (Abbas, Esmaeili, Abdollahi, & Sahebkar, 2017). Steviol has a special metabolism mechanism in which it is converted from Steviol glycoside to Steviol only (Gantait, Das, & Mandal, 2015). In an earlier study, similar justification was given about SGs that gastric juice and digestive enzymes cannot digest or rearrange it (Lebedev, Park, & Yaylaian, 2010). It was observed that all gastric enzymes were unable to digest Stevioside but the microflora of intestine can convert it to Steviol after hydrolyzation (Geuns et al., 2006; Hutapea, Toskulkao, Buddhasukh, Wilairat, & Glinsukon, 1997)

7. Phytochemical and antioxidant potential of Stevia

Oxidative stress is generated when production of a reactive oxygen species became too fast as it creates imbalance and biological system loss its ability to detoxify or repair that damage produced by reactive intermediates (Asmat, Abad, & Ismail, 2016; Maritim, Sanders, & Watkins Iii, 2003). In cell environment, life is stable due to reducing atmosphere which is maintained enzymatically by energy input that are metabolically attained. So, alteration or disturbance in this reducing state can greatly affect redox potential or create toxic effects thereby destructing the integrity of DNA. In human prospective, oxidative stress resides in many forms like Parkinson’s disease, Alzheimer’s, myocardial infarction, diabetes mellitus, atherosclerosis and chronic fatigue (Che, Wang, Li, Wang, & Zheng, 2016; Elchuri et al., 2005).

Numerous biochemical constituents are generated by plants including phenols as well as their oxygen substituted derivatives. These compounds have special role in plants serving as protection against microbial attacks and infections (Johnson, Wesely, Hussain, & Selvan, 2010). Stevia has limitless ability to produce phytochemicals, volatile oil components, flavonoids, sterebins A to H, triterpenes, gums, pigments, etc. (Siddique, Rahman, Hossain, & Rashid, 2014). These phytochemicals have enormous potential in minimizing risks free radicals that ultimately cause mutation, cancer and inflammation of body organs. Moreover, phytochemicals present in Stevia have been proved to be significantly effective for anesthetic, vasodilator cardiotonic, anti-inflammatory and austroinullin effect (Zia-Ul-Haq et al., 2011).

7.1. Total phenolic content (TPC) and total flavonoid content (TFC) of Stevia

TPC is a factor linked with countering the effects of oxidation occurred by enzymes action (Velderrain-Rodríguez et al., 2014). Enzymes like peroxidase and polyphenoloxidase used to work and reduces the antioxidant activity of food components by affecting the total phenol contents (Criado, Barba, Frígola, & Rodrigo, 2014). (Muanda et al., 2011) have calculated the concentration of TPC in Stevia as 20.85 mg GAE/g and have concluded that with the increase in pH of solution, oxidation of polyphenols increases thereby high concentration of phenolate molecules are formed. TPC and TFC in Stevia leaves and callus extracts were determined by (Kim, Yang, Lee, & Kang, 2011) and concluded that 1 mg Stevia leaves and callus extract contain 130.67 and 43.99 mg catechin. For flavonoids contents, they reported that 1 mg extract of Stevia contain 15.64 mg quercetin and callus extract have 1.57 mg quercetin. TPC and TFC from methanolic extracts of roots, leaves, stem and flowers of Stevia were determined by Singh, Garg, Yadav, Beg and Sharma (2012) who concluded that methanolic leaves extract have low level of flavonoid content as compared to root extract presented as 11.04 ± 3.16 and 16.75 ± 0.35 mg/g flavonoids.

Effect of high pressure processing treatment on the TPC of Stevia-based products like fruit beverages and their antioxidant activity, amount of Listeria monocytogenes, peroxidase (POD) and polyphenoloxidase (PPO) was determined by Barba, Criado, Belda-Galbis, Esteve and Rodrigo (2014). The application of HPP along with the usage of stevia resulted in the improvement of antioxidant and antimicrobial activity of fruit extract. So, total phenolic compounds in untreated sample with no Stevia was 185.5 mg GAE/L. However, Stevia products treated with HPP had 2261.1 mg GAE/L to 4050.8 mg GAE/L of TPC. They concluded that only HPP did not enhance antioxidant capacity infact addition of stevia along with HPP gives the best result. The addition of Stevia with HPP break the cell wall of L. monocytogenes thereby increasing the availability of phenolic contents and antioxidants (Andrés, Villanueva, & Tenorio, 2016; Carbonell-Capella, Barba, Esteve, & Frígola, 2013).

7.2. Antioxidant potential of Stevia

Metabolic processes occurring in our body produce free radicals. Due to environmental, pathogenic, physical, and chemical conditions the production of free radicals may increase significantly. The free radicals are produced when internal and external factors impact on body like drugs, smoke, pollutants, stress, etc. thereby imparting deleterious effect on our body such that they can, alter the structure of protein, lipids and DNA. These malformations may have drastic consequences on human body such as various human disorders as well as fasten the aging process (Afify, El-Beltagi, El-Salam, & Omran, 2012; Ruiz-Ruiz, Moguel-Ordoñez, Matus-Basto, & Segura-Campos, 2015).

Most commonly lipids are affected by free radicals which resultantly produce peroxides along with various odorous compounds imparting foul smell. Enzymatic action is disturbed when proteins are attacked by these free radicals. Nucleic acids when exposed to free radicals may results in carcinogenesis and mutagenesis. Antioxidant capacity due to phenolic compounds from different foods were assessed by the estimation of antioxidant assays like DPPH, ABTS, FRAP, etc. before and after colonic fermentation and digestion (Tavarini & Angelini, 2013). Free radicals take part during the oxidative stress which is a direct cause of pathogenesis of many diseases. Reduction or elevation of anti-oxidative substances takes place when the body equilibrium shifts towards free radicals, hence oxidative stress occurred (Flores, Wu, Negrin, & Kennelly, 2015; Nayak, Liu, & Tang, 2015).

DPPH is widely used in order to evaluate the free radical removing antioxidant ability of food material by stabilizing free radical with hydrogen ion donation (Gaweł-Bęben et al., 2015). DPPH free radical is a lipophilic radical and auto oxidation of lipid starts with its reaction. Owing to the least reactive nature of this radical; they combine with each other and resultantly a stable molecule is formed. It is shown that polyphenolic compounds when taken more than 1 g/day from the diet have controlling effect against carcinogenesis and mutagenesis (Shukla et al., 2009). Gasmalla et al. (2014) found that 10 µgm/mL Stevia leaves extract showed 3.38% and 100 µgm/100 mL leaf extract showed 10.15% of free radical scavenging activity. Results of various experiments showed that Stevia leaves extract have higher DPPH free radical scavenging activity as compared to Stevia callus extract with exception of 10 µg/mL. Shukla, Mehta, Mehta and Bajpai (2012) studied DPPH free radical scavenging activity and found that 1 gm of Stevia leaves extract gave 56.74 mg gallic acid which represents phenols and 1 gm of ethanolic extract gave 61.5 mg gallic acid. Periche, Koutsidis and Escriche (2014) determined effect of different heat treatments (50°C, 70°C, 90°C) with varying time durations (15, 20, 40 min) to Stevia leaves extract and antioxidant activity.

Various amounts of Stevia extract (20, 40, 50, 100, 200 µg/mL) had antioxidant activities like 40%, 46.84%, 51.35%, 64.26% and 72.37%, respectively. Singh et al. (2012) determined antioxidant potentials of methanolic extracts from Stevia root, leaves, stem and flower using DPPH and ABTS assays. ABTS radical scavenging activity assay as well as DPPH assay was used to analyze total antioxidant activity. Root extract showed highest (64.23 ± 8.35 mM) trolox equivalent antioxidant capacity (TEAC) for ABTS free radical scavenging activity; and leaves, stem, flower showed 56.26 ± 16.87, 49.28 ± 12.87 and 46.49 ± 13.13 mM, respectively. In order to determine anti-oxidative potential of extracts, superoxide dismutase (SOD), Catalase and peroxidase enzymatic assays were carried out and the root extract was found to have highest activities 4.84 ± 0.22, 8.6 ± 0.45 and 2.24 ± 0.05, respectively (Shukla et al., 2012; Singh et al., 2012).

7.3. Extraction methods of SGs/Steviosides

There are many steps to obtain phytochemicals from plant such as milling, grinding, homogenization and extraction. Among these steps, extraction is the main step for recovering and isolating phytochemicals from plant materials. Solvent extraction is mostly employed to extract desirable chemical constituents from food matrix (Oroian & Escriche, 2015). Extraction efficiency is regulated by phytochemical nature, method of extraction, particle size, polarity solvent, temperature, pH, time and sample nature (Stalikas, 2007). Various techniques that have been used to quantify SGs include chromatography adsorption, ion exchange, selective precipitation, membrane processes and supercritical fluid extraction. Rank and Midmore (2006) have refined by solvent (methanol and water) extraction methods followed by precipitation with calcium hydroxide and subsequent impurities removal with CO₂, while carbon dioxide is used to remove impurities and the same protocol was followed as adopted for sugar purification process in sugar industry. Steviosides were less soluble in hot water as compared to Rebaudioside A (Rank & Midmore, 2006). It has been extensively reported that usage of solvents like propylene glycol, glycerin, methanol/chloroform and ethanol is advantageous. Liu, Ong and Li (1997) have performed the extraction of Stevioside with hot methanol from dried leaves of Stevia. They have also used subcritical fluid extraction (Sub FE) for SGs, like Rebaudioside A, C and Dulcoside A. An efficient Sub FE technique was developed that used methanol as modifier co-solvent that resulted in remarkable 88% extraction efficiency.

Steviosides were also determined by extraction with supercritical fluid extraction (SFE) and subsequent quantification with HPLC (Pól et al., 2007). SFE using ethanol as co-solvent provides rapid extraction compared to previously used techniques. According to Erkucuk, Akgun and Yesil-Celiktas (2009) optimal mode of extraction elicited as 211 bar, 80°C which yielded 36.66 and 17.99 mg/g of Stevioside and Rebaudioside A. SFE of Stevia were subjected to liquid chromatographic analysis for estimation of Stevioside (Pól et al., 2007). There are several known techniques for glycosides quantification in plant material specially chromatography and spectroscopy techniques. Among the numerous sophisticated high tech. analytical instruments like HPLC, GC-MS and NMR however HPLC has been extensively employed in different cereals and plants (Bernal, Mendiola, Ibáñez, & Cifuentes, 2011). The quantification of Stevioside, Steviol and Rebaudioside A was carried out carefully through various strategies as showed in the scientific literature, including chemical detection and enzymatic hydrolysis (Gardana, Scaglianti, & Simonetti, 2010). Near Infrared (NIR) spectroscopy model and HPLC techniques were directly employed to measure steviosides content in leaves of Stevia rebaudiana (Yu, Xu, & Shi, 2011).

SGs have also been estimated by a qualitative LC-TOF method along with an authorized HPTLC procedure and densitometry detection (Morlock, Meyer, Zimmermann, & Roussel, 2014) while quantitatively being determined by NIRS procedure (Hearn & Subedi, 2009). Nowadays, desorption electrospray ionization mass spectrometry has been preferred for semi quantitative evaluation of SGs (Lemus-Mondaca et al., 2012). Fatty acid amides have been found discovered for very first time in Stevia. Therefore, they declared after investigation that wide range of components have been there in Stevia that have nutraceutical benefits ultimately benefiting health of masses (Jackson et al., 2009).

8. Therapeutic remunerations of Stevia

Stevia has been recommended to diabetic patients owing to its non-nutritive properties and approved by the FDA as a dietary supplement. In ancient times, use of Stevia has been reported in treatment of various maladies. Stevia leaves have been recommended to cure different ailments like obesity, renal diseases, CVDs, cancer, inflammatory bowel disease (IBD), dental caries, etc. (Gupta, Purwar, Sundaram, & Rai, 2013). Toxicological studies have shown that Stevia play a defensive role against carcinomas, mutagenesis, teratogenesis, certain allergic responses, cause no genetic defects in body and beyond sweetness impart anti-hypertensive, diuretic, anti-viral, anti-diarrheal, anti-cariogenic, anti-microbial, immunomodulatory and chemo-preventative activities (Abou-Arab et al., 2010; Yildiz-Ozturk, Nalbantsoy, Tag, & Yesil-Celiktas, 2015) .

8.1. Glucoregulation

Diabetes mellitus is a disease described as hyperglycemia and varying degrees of an insufficient insulin effect. There are approximately 177 million people with diabetes worldwide according to the World Health Organization (W. H. Organization, 2016). Traditionally Stevia leaf extract has been used in the treatment of diabetes (Megeji, Kumar, Singh, Kaul, & Ahuja, 2005). It was observed that in both animals and humans Stevia has the ability to increase the insulin effect on cell membranes, increase insulin production, and stabilize glucagon secretion as well as blood sugar levels, and improved glucose tolerance to ingested carbohydrates and lower post-prandial blood sugar levels. It can be stated that Stevia provide a comprehensive set of mechanisms that alter the type II diabetes and its ultimate complications. Thus, SGs or Stevioside of Stevia leaf can be used as a replacement of sugars to support healthy glucose regulation (Gupta et al., 2013).

8.2. Blood pressure regulation

Upsurge in blood pressure from certain level or a standard measurement is known as hypertension or high blood pressure. If a person has 140 mmHg systolic and 90 mmHg diastolic pressure, he/she is declared as hypertensive. The high blood pressure in those veins that are already in medium size or narrow sized arteries increases the pressure of blood and causes many problems like they become thick and hard to pump blood towards whole body from heart, it can cause a risk of stroke development leading to heart attack (W. H. Organization, & Group, I. S. o. H. W, 2003). Stevia has the ability to normalize the blood pressure as well as regulation of heartbeat for cardiopulmonary signals. Extraction of stevia leaves by hot water capable in regulation of blood pressure in human. A lot of studies indicated that stevia and its compounds have the hypotensive and diuretic capacity. Stevia works just like the blood pressure lowering medicines at membrane level, these medicines are known for their hypotensive properties by dilating the walls of arteries to decrease the pressure of blood. Findings of many studies expressed that Stevia has the ability of lowering the blood pressure by dilating the arteries (Gardana et al., 2010).

Phytosterols are plant-based compounds and which are present in wax that are secreted by leaves and its properties act against defects of cardiovascular system (Marković, Đarmati, & Abramović, 2008). Steviosides and their derivatives have vasorelaxation properties (Wong et al., 2004). To evaluate these properties of Stevia, a human trial was conducted in which 106 hypertensive patients were enrolled and were given 750 mg of Stevioside or placebo capsules daily (Chan et al., 2000). The individuals who were taking stevioside, indicated significant reduction in blood pressure with no significant side effects observed. The effect of extract of stevia was analyzed in 20 female hypercholesterolemic patients by taking 20 mL of extract in 200 mL of water indicating the reduction in cholesterol, LDL and triglycerides with increment in HDL. It shows the hypolipidemic attributes of stevia and maintaining the cardiovascular health status of people (Gupta et al., 2013; Sharma et al., 2015).

8.3. Anticancer benefits of Stevia

Cancer is defined as the disorder of body cell DNA in which chemistry of DNA varies that aggravate with the passage of time (Goyal et al., 2010). Stevia has been extensively used as sweetener and in additive form as well. Over years nothing has been reported to be associated with Stevia for toxicity, carcinogenicity, auto immune disorders, mutation, etc. caused or with its metabolites in mammals including certain animals and especially human, therefore can be regarded as safe for human consumption (Chrchanioti, Chanioti, & Tzia, 2016). Different bioactive components have been reported to be working against tumors, carcinomas, etc. Stevia leaves are rich in bioactive moieties like Labdane sclareol, which has anti-cancer anti-inflammatory and cytotoxic removing attributes (Kaushik, Narayanan, Vasudevan, Muthukumaran, & Usha, 2010).

Stevia polyphenols have been reported to possess properties inhibiting tumor initiation, propagation and ultimately protecting the body against certain maladies. SGs particularly Steviosides have the capability to block or minimize the activity of tumor propagation (Mizushina et al., 2005). Rebaudioside A has been extensively investigated for its safety perspective including carcinogenesis, mutation by employing Ames test in which bacterial reverse mutation was checked by using Salmonella typhimurium and Escherichia coli as standards. The results depicted that Reb A was found to be non-mutagenic in both bacterial strains. Another study was done on human lymphocytes in order to establish the toxicity status of Rebaudioside-A. Male Wister rats were administrated 2000 mg/kg body wt. in a single dose with subsequent 16 h observation in order to check any toxicity signs of Stevia. No substantial toxicity affect have been seen in rats that leads to carcinogenesis (Williams & Burdock, 2009). Stevioside have been examined and they retard the tumor promoting agent which promotes tumor formation in mice skin. Anti-tumor and anti-carcinogenicity affect has been recorded wen Stevioside has been administrated against urinary bladder tumor diseased cells. Therefore, neoplastic or pre-neoplastic lesions have not been seen in any of the tissue (Takahashi et al., 2012).

8.4. Renal functions regulations by Stevia

There are almost 70 million individuals present with different types of diseases in world. Due to chronic level of renal ailments 400,000 deaths were occurred in 1990 and almost 735,000 deaths were reported in 2010 (Bos-Touwen et al., 2015). Kidneys play an important role in maintaining the environment of body by homeostasis. Many types of ailments effect the regular functioning of renal system by disturbing the nephron structure. (Shivanna, Naika, Khanum, & Kaul, 2013) analyzed the effects of Steviosides on kidney functions in hypertensive and normal rats. Stevioside was found to be a vasodilator and hypotensive properties as well as diuresis and natriuresis in hypertensive and normal rats. In hypertensive and normal rats, glomerular filtration rate and the rate of kidney plasma flow was found to be increased by the administration of Steviosides at constant rate. Effect of Stevia and its components on renal functioning was evaluated on transepithelial in proximal kidney tubes of rabbits. The results were found that Steviosides inhibits the transepithelial at the dose level of 0.70 mM (Jutabha, Toskulkao, & Chatsudthipong, 2000). Abbas et al. (2017) conducted a study trial to evaluate the inhibitory effects of the Steviol and its derivatives on the growth of cyst. The findings revealed that Steviol is a good component in the treatment and cure of polycystic renal ailments. Steviol and its bioactive moieties are the natural plant-based drugs for polycystic kidney disease treatment (Brahmachari, Mandal, Roy, Mondal, & Brahmachari, 2011).

8.5. Obesity control by Stevia

Most prevalent nutritional malady worldwide is obesity in which excess fat aggregated in different parts of body. If the excess body weight is more than 20% as compared to ideal body weight of body, it is also defined as obesity in clinical terms. Physical inactivity, unhealthy food selection and habits, over consumption of food have contributed in prevalence and alarming increase in obesity. Obesity is directly linked with calorie intakes, higher the intakes of calorie dense food items, greater is the incidence of obesity. In this scenario, an affective weight management strategy is to be adopted that helps in minimizing obesity chances. Low or zero calorie sweeteners are the best choices for people who have high inclination towards desserts (Miller & Perez, 2014). Stevia being zero caloric, do not metabolize and spike in blood glucose level, have been measured in such a way that 1 g of crude extract of Stevia is 100–150 times sweeter than sucrose (Pradhan, 2016). Therefore, Stevia can be considered to be best substitute of common table sugar, help in weight management by restricting or minimizing calorie intake and it has also been reported that high doses of Stevia resulted in significant weight reduction in animals (Curry, Roberts, & Brown, 2008). If daily intake of 95 g (24 tsp) is regulated in diets by completely replacing sugar with Stevia powder results in net deficit of 380 cal/day or weight loss of 1 pound in 9–10 days. Another important aspect of Stevia as sweetener is that it minimizes the cravings for fatty foods and sweets, which is also an important strategy to manage weight (Gardner et al., 2012).

8.6. IBD management

Inflammation of small intestine and colon is known as IBD. It is basically group of conditions and exists in two prime forms namely ulcerative colitis and Crohn’s disease. Patients from both sexes between the ages of 15–30 years are most vulnerable. In all types of IBDs, exact cause remained unknown, however natural phenomena involving autoimmune and genetic predisposition play a crucial role in development and persistence of IBDs (Knight-Sepulveda, Kais, Santaolalla, & Abreu, 2015). Polyphenolic components used to play potent role in regulation of metabolic syndrome and provide anti-inflammatory benefits to body. Stevia being rich in polyphenols including TPCs, TFC and certain other phenolic acids that are helpful in defending body against harmful diseases. Contraction of intestinal smooth muscles leads to hyper motility of intestinal microvilli causing diarrhea. Inhibition of intestinal contraction has been observed in different animals fed on Stevia powder along with their fodder (Olendzki et al., 2014; Shiozaki, Fujii, Nakano, Yamaguchi, & Sato, 2006).

8.7. Dental maladies management

Dental caries (tooth decay), is the most prevalent disease worldwide. The individuals including babies and elders are prone to this during whole life span. Microorganism of oral cavity used to produce organic acids metabolites leading to demineralization of enamel and ultimately causing proteolytic deterioration of tooth structure. Dietary carbohydrates are fermented by various microbes particularly Streptococcus mutans, Lactobacillus casein and Streptococcus sanguis. Utilization of calorie dense nutritive sweeteners on daily basis furnish energy in carbohydrates form, aggravating cavities, plaque and gingivitis formation due to microbial growth and their activity (de Slavutzky, 2010). Therefore, in order to cope up with these severe dental issues, calories dense sucrose and artificial sweeteners needs to be replaced with other natural sources that provide zero caloric affect and are not destructive to consumer health (Matsukubo & Takazoe, 2006). In this regard, Stevia can be considered as best alternate to nutritive sweeteners having the properties of zero caloric and are famous as non-nutritive sweeteners. Stevia hold the bacteriocidal and bacteriostatic attributes thereby minimizing the chances of plaque and gingivitis. Stevia extracts along with its metabolites are non-nutritive and tends to reduce glucan induced accumulation of cariogenic organism. Therefore, Stevia have been proved to be ideal in provision of oral health perks (Gupta et al., 2013).

9. Product development with Stevia

Food processing industries including confectionaries, baking industries, beverage industries and a number of other are replacing sucrose and other intense sweeteners with stevia powder and extracts to cut short the price ultimately providing natural products with greater consumer acceptability. Increasing awareness and potential perks of Stevia have urged people to use Stevia in their daily routine food items like ready-to-eat cereals, yoghurt, beverages, sea foods, etc.

9.1. Temperature stability of Steviosides

Stevia can be used in various food products at high temperature and it remains stable against a broad range of pH, it resists against fermentation and it is also acid stable. No caramelization or browning was recorded with the addition of Stevioside and rebaudioside A in food products processed at elevated temperatures (Abou-Arab et al., 2010). Steviosides are heat stable at temperature 95°C as they do not decompose at this elevated temperature and utilized affectively as sweetener in baked food stuffs. Carbonell-Capella et al. (2013) have claimed that Stevia powder and extracts can be employed at high processing temperatures i.e. 200°C with proper sweetening ability and allied potent benefits as well. Incubation of Stevioside for one hour at 120°C was found to be affective without any structural and functional disintegration. They have also concluded that decomposition starts as the processing or incubation temperature raised from 200°C. Stevia do not exhibit specific taste and color of browning and caramelization, therefore recommended to be used in combination with sucrose for better product quality in baked items and beverages. Product stabilization and textural deformities have been seen when 100% Stevia incorporation have been carried out (Alizadeh, Azizi-lalabadi, Hojat-ansari, & Kheirouri, 2014).

9.2. pH stability of Steviosides

Steviosides have been reported to be stable in wide pH range and temperature (Panpatil & Polasa, 2008). They remained stable without showing any degradation under pH ranges of 1–10 when dissolved for more than 2 h at 60°C, however very minimal loss of up to 5% has been reported when heated up to elevated temperature of 80°C with pH ranging from 2 to 10. On the other hand, when exposed to highly acidic environment of pH 1 at temperature of 80°C for 2 h resulted in complete decomposition of Steviosides (Abou-Arab et al., 2010). In the same way steviosides remained stable between pH ranges of 3–9 while rapid decomposition started if pH raised from 9 at temperature up to 100°C for 1 h (Buckenhuskers & Omran, 1997). Rebaudiside A remained stable and gave sweetness in cola and lemon lime when it is stored for 26 weeks. Rebaudiside A gave acceptable sweetness for 26 weeks when it is used in formulation of chewing gum. It is observed that Rebaudiside A can tolerate pasteurization temperature (88^oC for 5 min) and resist the fermentation process when it is used in formulation of plain yogurt and it gave considerable sweetness when product was stored for 6 weeks (Prakash, Markosyan, & Bunders, 2014).

9.3. Steviosides stability in product development

Confectionary and bakery industries are using Stevia, solely as well as in combination with sucrose to minimize the usage of calorie rich sweeteners. In different products, Stevia powder and extracts have been used with good sweetness level. Stevioside and sucrose used to impart synergistic affect to each other when added in peach juice in such a way that 160 mg/L of Stevioside and 34 g/L of sucrose incorporation do not impart any bitter or metallic aftertaste to sensory attributes of final product. When we compare Stevia with the saccharine in context of its metabolism it was found that Stevia was not completely metabolized by human body providing very low calories but saccharine is not completely metabolized and contributes to various diseases (Yadav & Guleria, 2012). Zahn, Forker, Krügel and Rohm (2013) used Rebaudiside A, as natural sweetener to replace sugar along with different bulking agents to provide bulkiness to muffins. Texture, color, chemical analysis and sensory attributes showed that muffin with blend of inulin or polydextrose and 30% Rebaudiside A exhibited good results and very close to the reference in which 100% sugar was used. When inulin, polydextrose and 30% Rebaudiside A was added then energy of muffin was reduced by 5 kJ/100 kJ (Wang et al., 2015; Zahn et al., 2013).

Cookies have been recommended as a better utilization of flour than bread because of they are in ready to eat form, excellent eating quality, wide consumption and extensive shelf life as compared to bread (Okpala & Chinyelu, 2011). Abdel-Salam, Ammar and Galal (2009) formulated and assessed a formulated functional yoghurt cake. They made cakes by replacing sucrose with Stevia water extract as sweetening agent and employing functional ingredients in making of functional yoghurt cake. They used Stevia water extract instead of sugar, olive oil instead of butter, skim milk in place of full cream milk, egg white for whole eggs and whole wheat flour instead of 72% extraction wheat flour. Lemon rind and orange peels incorporated to the yoghurt with Stevia water extract. They sensory evaluated the both formulated yoghurt cake and regular yoghurt cake in which texture, flavor, color, odor, appearance and overall acceptability was visualized. They found that sensory attributes of both formulated yoghurt cake and regular yoghurt cake obtained acceptable scores. The yoghurt cake which was made for diabetic patients showed very low food energy and very low calorific value. Functional yoghurt cake having high amount of carbohydrates and fibers may be very beneficial to enhance the health of blood vessels in persons which are suffering from metabolic disorders possibly will reduce the chances of cardiovascular disease. When Stevia leaves powder was added in cakes its texture became firmer as compared to regular yoghurt cake with its hardness raised by 3176 g as correlate with hardness of regular yoghurt cake which was the 3161 g and toughness was enhanced. Garcia-Serna, Martinez-Saez, Mesias, Morales and Del Castillo (2014) added different proportions of stevia by replacing the sugar and added coffee silver skin as bulking agents in cookies and separately added maltitol by replacing sugar 100% sugar replacement with Stevia increases the moisture thereby affecting the texture of cookies that ultimately affect the overall acceptability (Kulthe, Pawar, Kotecha, Chavan, & Bansode, 2014). This reason may cause reduction in shelf life of the cookies. When silver skin is added in the cookies then reduction in moisture level is observed. Thickness of Stevia cookies and maltitol cookies was similar but when silver skin is added in combination with Stevia, thin cookies were attained (Manisha, Soumya, & Indrani, 2012).

10. Conclusion

Stevia leaves powder and extract are high intensity non-nutritive natural health promoting sweetener. Stevia has been found as a good source of nutritional constituents and functional properties for value addition. Stevia being a promising high phenolic and flavonoid contents used to act as good antioxidant. Minerals have been found to in appreciable amounts like sodium, potassium, phosphorous, magnesium, iron, manganese, copper, nickel and cobalt. Palmitic acid, linoleic acid, linoleic acid and oleic acid have been found in good concentration. Stevia has been proved to be beneficial in modulation of glucose, regulation of blood pressure and renal functions, anticancer, obesity control, management of IBD and dental maladies. Food processing industries, including confectionary, baking, beverage and a number of other are replacing sucrose and other intense sweeteners with stevia powder and extracts that ultimately providing natural products with greater consumer acceptability. In addition to be used as intense sweetener, Stevia helps in preparation of functional and medicinal foods that augment health status of masses.

Acknowledgements

Authors, gratefully acknowledge the financial support from Higher education commission (HEC), Islamabad-Pakistan.

Conflict of interest statement

The authors declare that there are no conflicts of interest.