The influence of horse mint (Mentha longifolia) leaves on antioxidant activity and lowering lipid peroxidation in roasted coffee powder

Abstract

The present research investigation sought to learn more about the impact of various quantities of Mentha longifolia leaves powder (MLLP) on the content of phenolics, antioxidant effectiveness, consumer approval, as well as lowering lipid peroxidation in roasted coffee (RC) powder. MLLP was added at 0%, 0.25%, 0.50%, 0.75, 1.00%, and 1.25% of the roasted coffee (RC) weight. Total phenolics (TP), total flavonoids (TF), as well as the antioxidant activity which was assessed using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical of green coffee (GC), RC, MLLP, and binary blends of RC and MLLP were assessed. The oxidative indices of coffee oil samples have been investigated during storage intervals. Furthermore, the sensory qualities of RC fortified with various dosages of MLLP were investigated. Findings MLLP showed TP contents (TPC, 2600.15 mg/100 g DWb) which was 1.83 fold greater than those reported in roasted coffee (RC) powder. The results also revealed that when the MLLP quantity increased, TPC of the investigated coffee samples significantly increased. TPC of the produced coffee increased from 1417.30 to 1432.18 mg GAE/100 g DW when MLLP inclusion incremented from 0% to 1.25%. TFC of RC supplemented with 0.5%, 0.75%, 1.00%, and 1.25% MLLP was found to be around 1.04, 1.04, 1.05, and 1.06 times greater than that of control coffee samples without MLLP addition, respectively. DPPH radical-scavenging activity increased significantly from 67.74% in control samples (without MLLP enrichment) to 69.59, 69.74, 70.32, and 71.45 (percent DPPH inhibition) in RC samples enriched with 0.50%, 0.75%, 1.00%, and 1.25% MLLP, respectively. The acid, peroxide, P-Anisidine, and Totox values of RC enriched with 1.25 MLLP were around 2.08, 1.76, 1.64, and 1.70 fold lower, respectively, than in the control sample without MLLP addition. The sensory scores of RC containing 0.50% and 0.75% MLLP were significantly higher (p ≤ 0.05) than control samples.

Keywords:

• food intake
• antioxidant
• public health
• diet supplementation
• fatty acid

PUBLIC INTEREST STATEMENT

Coffee and its derivatives have been shown to be a good source of phytochemicals in the human diet. Radical-scavenging activity increased significantly from 67.74% in control samples (without horse mint leaves enrichment) to 69.59, 69.74, 70.32, and 71.45 in roasted coffee samples enriched with 0.50%, 0.75%, 1.00%, and 1.25% horse mint leaves, respectively.

1. Introduction

Coffee trees are members of the Rubiaceae family, genus Coffea (Davis et al., 2006). Coffee is considered to be one of the most important global commodities, and it is globally distributed as green coffee beans. Coffee is an important export product of more than sixty tropical and subtropical countries (FAO, 2016; Sakiyama & Ferrao, 2015; Vieira, 2008). Coffee and its derivatives have been found to be an excellent provider of phytochemicals in our diets (Ribeiro et al., 2014). It also contains additional favorable bioactive compounds for people’s health (caffeine, trigonelline, as well as chlorogenic acids), making it an appealing therapeutic food product (Ribeiro et al., 2016). Coffee has recently become a major topic of investigations due to potentially beneficial health advantages (Messina et al., 2015). Coffee, especially green beans, contain a high concentration of chlorogenic acid (CGA), a form of polyphenols (Revuelta-Iniesta & Al-Dujaili, 2014). and the CGA has numerous of health benefits, including antifungal, antiviral, antibacterial, antioxidant, as well as other biological functions (Bharath et al., 2015). Coffee is an antiobesity, anti-diabetic, hepatoprotective, antioxidant, anti-genotoxic, anti-inflammatory, cytotoxic, and immunomodulator substance as well as a tumor metastatic disease, vascular development, cell cycle progression, and proliferation of cells inhibitor (Chen et al., 2014; El-Abhar & Schaalan, 2014; Gaascht et al., 2015; Gokcen & Sanlier, 2017; Pan et al., 2016). Consumption of 3–4 cups of coffee per day reduces mortality risk in adult males (Grosso et al., 2015) and suppresses inflammatory processes, limiting the risk of cardiovascular and other inflammatory disorders in postmenopausal women (Peasey et al., 2006). Nevertheless, coffee use has a negative impact on health. Caffeine has a detrimental impact on the appetite levels (Willett et al., 1985), and it can have an adverse effect on lipid profiles depending on how the beverage is prepared (Laaksonen et al., 2008). The inclusion of additional substances into coffee-based drinks developed their composition and had an important influence on the distribution and intake of specific nutrients during digestion process (El-Anany et al., 2021; Quan et al., 2020). With increasing consumer awareness of food safety and quality, there is a strong demand for preservative-free food and the use of natural tastes, herbs, and aromatic medicinal plants, which have gained popularity due to their powerful anti-inflammatory and antimicrobial behaviors (Durak et al., 2017; El-Anany et al., 2021). In this respect, Mentha longifolia L(Lamiaceae (Labiatae), also known as wild mint or horse mint, is one of the most valuable medicinal plants with medicinally validated natural components (Farzaei et al., 2017). Mentha longifolia (wild mint) is a plant of the Lamiaceae family that grows widely in tropical areas around the world (Hussain et al., 2010). Since ancient times, various herbal and alimentary products derived from Mentha species have been used to treat stomach discomfort, diarrhea, flatulence, coughs and flu, vomiting, irritable bowel syndrome, gallbladder as well as bile ducts, herpes, and likely skin infections such as acne and pigmentation (Hussain et al., 2010, 2011). Green mint has a very strong effect on the nervous system. The boiled extract of leaves has an anti-infectious, antiflatulence, and anti-inflammatory action (particularly of the gastrointestinal system); it was recommended in viral liver infection and diarrhea, stomach acidities, as well as aerophagia to promote the process of digestion (Mkaddem et al., 2009). Mints’ active characteristics are based on their abundant volatile oils, which contain a diverse spectrum of terpenes and terpenoids (Sharopov et al., 2012). The active components in Mentha longifolia are derived from the mevalonate and shikimate pathways. The former generates Mentha longifolia’ volatile terpenes, most commonly ketones such as carvone, piperitone, piperitenone, and corresponding epoxides (Patonay et al., 2020). Mentha’s biological function has been linked to the volatile compounds, although phenolic substances may also play an integral role (Fecka et al., 2004). The phenolic acids content (PAC) has been predicted to be 2.7–5.5%, particularly rosmarinic acid, caffeic acid, and protocatechuic acid. The flavonoid quantity is predicted to be 3.0–6.3% (Olennikov & Tankhaeva, 2010), especially luteolin-7-O-rutinoside, eriocitrin, narirutin, as well as hesperidin being the most abundant (Baliga & Rao, 2010; Fecka et al., 2004). Pulegone, isomenthone, 1,8-cineole, borneol, and piperitenone oxide are the primary components of M. longifolia. Recent research found that 4% to 6% incorporation of M. longifolia extracts improved immuno-system (Raissy et al., 2022). The aim of the current study was to investigate the impact of adding different quantities of Mentha longifolia leaves powder (MLLP) on the content of phenolics antioxidant properties, consumer approval, and lowering lipid peroxidation in roasted coffee powder.

2. Materials and methods

2.1. Preparation of roasted coffee powder

Green coffee (GC) beans (Coffea arabica) were obtained from from a privately owned coffee producer in Giza, Egypt. GC beans were roasted for 15 minutes at 225°C in an electric oven (Thermo scientific, model Heratherm OMS60, Germany). Roasted coffee (RC) beans were pulverized in a coffee processor (Braun Burr Coffee Grinder—KG7070) and implemented by means of a screen with a mesh size of 0.75 mm.

2.2. Dried Mentha longifolia leaves powder (MLLP)

Fresh mint plants (Mentha longifolia) have been purchased from Al-Madinah al-Munawwarah city’s local markets in Saudi Arabia. Initially, the fresh green leaves were separated from detached from the stems and branches. To remove dust and other impurities, the leaves were thoroughly rinsed with chlorinated water (50 ppm). The cleaned leaves were drained to remove excess water and dried for three days (3 days) in an oven (Selecta, Barcelona, Spain) at 40 °C. The dried leaves were milled (Kenwood, China, Model KM001 (0067078)) to a mesh size of 0.75 mm. The powdered leaves were vacuum-packed and stored in a refrigerator (51 °C) for additional use.

2.3. Roasted coffee and dried Mentha longifolia leaves powder binary blends

Dried Mentha longifolia leaves powder (MLLP) was blended with roasted coffee (RC) powder at levels of 0%, 0.25%, 0.50%, 0.75%, 1.00%, and 1.25%, respectively. The prepared samples of coffee were carefully sealed in paper-aluminum foil-polyethylene pouches and kept at room temperature for a period of six months (6 months) for subsequent investigation.

2.4. Coffee beverage preparation

In a stainless-steel coffee vessel, ten grams of roasted coffee samples were combined with 100 mL of drinkable water. The mixture was swirled continuously for 30 seconds with a small teaspoon before being heated lower than the boiling point of water (93°C-95°C) for two minutes. The freshly brewed beverage was poured into coffee cup.

2.5. Extracts preparation

The extraction procedure was performed out in accordance with El-Anany et al. (2021). Separately, ten grams of assessed coffee samples were extracted overnight at room temperature on a shaking device with 70% water-based ethanol (200 mL). The resulting substance was then passed through a WhatmanNo.1 filter paper. Buchi R-200 4 L Rotary Evaporator V-800 Controller B-490 system was used to concentrate the extract solution at 45°C. Dried extracts were kept at −20°C in darkness for additional investigation.

2.6. Determination of total phenolic contents

The total phenolic content (TPC) has been assessed using the spectroscopic method described by El-Anany et al. (2021). The Folin-Ciocalteu test reagent was used in order to determine the total phenolic content (TPC). Total phenolic content was calculated by extrapolating a calibration curve established by gallic acid solution. TPC was calculated as milligrams of gallic acid equivalent (mg GAE) per 100 grams of dry material.

2.7. Determination of total flavonoid content

The total flavonoid content (TFC) has been quantified using a colorimetric technique developed by Alkaltham et al. (2020). The TFC content was expressed as the catechin equivalent per 100 grams of dry matter of the material being studied (mg CE/100 g DW).

2.8. DPPH radical scavenging activity assay

The radical-scavenging activity of ethanolic coffee extracts was measured using the method reported by Mohammed et al. (2023). An aliquot (100 μL) of ethanolic coffee extract was combined with 5 ml of DPPH radical 6 × 10–3 M methanolic solution. The resulting mixture had been thoroughly stirred before being placed in the dark for thirty (30 minutes) at room temperature. The absorbance has been determined at 517 nm using a UNICO UV/VIS-2100A spectrophotometer (Dayton, USA) versus a blank sample.

The percentage of inhibition was determined as (%) = (Abs control—Abs sample)/Abs control × 100.

Where Abs control is the absorbance of the DPPH radical +methanol and Abs sample is the absorbance of the DPPH radical + sample extract/standard.

2.9. Extraction process of coffee oil

At the end of storage periods 0, 1, 2, 3, 4, 5, 6 months of storage at room temperature, one hundred grams of control coffee sample as well as those incorporated with different proportions of MLLP were individually mixed with 1000 ml of chloroform/methanol mixtures (2: 1 wt/wt). The resulting mixtures had been stirred using a conical flask at room temperature (25 °C) for a period of 48 hours. The sample was subsequently centrifuged for 60 minutes at a speed of 5000 rpm. The phase consisting of organic matter was gathered, and the solvent had been evaporated at 40 °C in a vacuum rotary evaporator (Buchi heating bath B-490, Buchi rotavapor R-200, Switzerland). The oil was kept in containers made of glass at −18 °C until its next application.

2.10. Acid value determination

The acid value was measured using the AOCS official procedure Cd 3a-63 (AOCS, 2004). The result was reported as the milligrams of KOH required to neutralize the free fatty acid in one gram of oil sample.

2.11. Determination of peroxide value

The peroxide value (PV) has been determined using the AOCS official procedure Cd 8b-90 (AOCS, 2005). PV is measured in milliequivalents of peroxides per kilogram of oil sample.

2.12. p-Anisidine value (p-AnV)

The p-anisidine value (p-AnV) was used to determine the aldehyde content. The original methods specified in AOCS Official Technique Cd 18–90 1992 were used to determine p-AnV.

P AV = 25 (1.2 As—Ab)/m

where As indicates the absorbance of the oil solution after reaction with P-anisidine reagent; Ab indicates the absorbance of the oil solution; and m represents the sample’s mass (g).

2.13. Totox value

To estimate the primary and secondary oxidation products of oil, the total oxidation value (Totox) was utilized. 2(PV P-AV) was used to compute the Totox value (Cong et al., 2020).

2.14. Sensory evaluation

The sensory assessment of the produced coffee samples was performed by 150 semi-trained panelists (aged 20–45 years) randomly selected from Qassim University’s College of Agriculture and Veterinary Medicine in Buraydah, Saudi Arabia. Participants sat in individual cabins in an air-conditioned room (25°C 1°C), during the evaluation process fluorescent daylight bulbs provide illumination. Three-digit codes were used for labeling coffee samples. The appearance, odor (orthonasal perception), taste, as well as overall acceptance of coffee beverage samples were assessed using a ten-point hedonic scale that ranged from 1 (dislike highly) to 10 (like exceedingly). A cup of water provided for cleaning the palate between testing. The sensory evaluation met the sensory research requirements established by the Auckland University of Technology Study’s Ethics Committee (AUTEC ethic application 16/340).

2.15. Statistical analysis

SPSS (version 20) was applied to analyze the results. The data were statistically examined in five replicates, excluding the sensory evaluation results (n = 150). The variation in values has been assessed by one-way ANOVA with a threshold for statistical significance of 0.05. Duncan’s multiple-range test was implemented to compare the results.

3. Results and discussion

3.1. Phenolic content, flavonoids content and antioxidant activity of green coffee, roasted coffee (RC), MLLP, and binary blends of RC and MLLP

Several studies have shown that the antioxidant capacity of certain fruits and vegetables is closely linked to their total phenolic content (TPC). Antioxidants are substances that can delay or prevent the oxidation of lipids or other molecules by prohibiting the initiation or progression of oxidative chain reactions (Niroula et al., 2019). Table 1 shows the TPC (mg GAE/100 g DWb) of green coffee (GC), roasted coffee (RC), dried Mentha longifolia leaves powder (MLLP), as well as binary mixtures of RC and MLLP. TPC of GC samples was found to be 1612.14 mg GAE/100 g. However the TPC of roasted coffee was 1417.30 mg/100 g DWb. The reduction in TPC can be attributed to the fact that chlorogenic acid molecules constitute more than half of the phenol content in GC beans. Roasting process of coffee beans produces a unique flavor, aroma, along with dark color in brewed coffee. Maillard reaction products are the major antioxidants in brewed coffee since most free chlorogenic acid is broken down during roasting (Liao et al., 2022). These findings are comparable with those of Alnsour et al. (2022), who stated that TPC of 52 samples of arabica coffee items collected from different areas with different roasting grades fluctuated from 1492 mg/100 gm to 1655 mg/100 gm in dry matter. These variations in phenolic concentration can be attributed to cultivation methods, roasting techniques, and coffee source (Król et al., 2020). MLLP exhibited a high TPC content (2600.15 mg/100 g DWb), which was 1.83 times that of RC powder. The TPC of five Mentha spp. ranged from 14.7 to 43.2 mg of GAE/g dry weight in a research investigation carried out by Benabdallah et al. (2016).

Table 1. Phenolic content, flavonoids content and antioxidant activity of green coffee, roasted coffee (RC), MLLP, and binary blends of RC and MLLP

Sample	Total phenolic content mg GAE/100 g DW	Total flavonoids content (mg CE/100 g DW)	DPPH radical scavenging (%)
Native materials
Green coffee (GC)	1612.14 ^b±17.98	216.17^b±7.88	74.25^b±5.14
Roasted coffee (RC)	1417.30^e±16.66	171.13^ef± 9.02	67.74^d±6.12
Dried Mentha longifolia leaves powder (MLLP)	2600.15^a±32.84	495.05^a±8.19	95.19^a±4.07
Roasted coffee (RC)/MLLP blends
RC (g): MLLP (g)
RC : MLLP (100: 0)	1417.30^e±19.62	171.13^ef±12.08	67.74^d±4.55
RC : MLLP (99.75: 0.25)	1421.00^d±17.02	177.80^e±13.87	68.11^d±5.26
RC : MLLP (99.50: 0,50)	1424.37^cd±12.99	178.09^d±8.09	69.59^cd±6.74
RC : MLLP (99.25: 0.75)	1426.28^cd±7.85	179.26^d±7.75	69.74^cd±2.76
RC : MLLP (99.00: 1.00)	1429.89^cd±42.61	179.73^cd±8.20	70.32^c±3.81
RC : MLLP (98.75: 1.25)	1432.18^c±32.17	182.03^c±14.08	71.45^b±4.12

The values represent the means ± standard deviations (SD) of five determinations.

Means in a column with distinct letters vary significantly (P ≤ 0.05).

Table 1 also displays the effect of enriching RC with different levels of MLLP on the content of total phenolics. MLLP is an excellent source of phenolic molecules, which contribute to the strengthened RC’s high antioxidant capacity. The results showed that roasted coffee samples enriched with 0.25–1.25% MLLP had significantly greater phenolic contents than control RC samples without MLLP addition. The results additionally showed that the TPC of the investigated coffee samples increased significantly as the MLLP quantity increased. When MLLP incorporation was increased from 0% to 1.25%, the TPC of the produced coffee increased from 1417.30 to 1432.18 mg GAE/100 g DW. Coffee has been identified as an important provider of antioxidant compounds owing to the high level of alkaline substances, flavonoids, and phenolic substances. Coffee consumption therefore correlates with healthier life (Alnsour et al. (2022). The total flavonoids content (TFC) (mg CE/100 g DW) of GC and RC was 216.17 and 171.13, respectively (Table 1). These results are consistent with those of El-Anany et al. (2021), who found that the TFC of RC grains was 186.39 mg/100 g dry matter. Appropriate roasting could decompose the condensed tannins into lower molecular weight flavonoids particularly anthocyanin, consequently enhancing the effectiveness of free TFC (Ahmad et al., 2018). TFC in MLLP was 495.05 mg/100 g DWb, which was 2.89 times higher than in roasted coffee (RC) powder. The results additionally indicate that roasted coffee (RC) samples enriched with 0.25%-1.25% MLLP have significantly greater TFC than non-supplemented coffee samples. The results also indicate that when MLLP levels were increased, the TFC of the enriched coffee samples improved significantly. TFC of roasted coffee enriched with 0.5%, 0.75%, 1.00%, and 1.25% MLLP was found to be around 1.04, 1.04, 1.05, and 1.06 times higher than that of control coffee samples without MLLP addition, respectively. The ability of flavonoids to act as antioxidant substances is one of their most important properties (Arora et al., 2000). MLLP includes about 50 flavonoids. Flavones, flavonols, and flavanones are three types of flavonoids that can be found in free form as well as glycosides. They range in concentration from traces to 1000 mg/kg dry plant. Apigenin is the most common flavone in MLLP. MLLP also contains four flavanones, including naringenin, eriodyctiol, hesperetin, as well as 4’-methoxy-naringenin (Patonay et al., 2017).

One of the most widely used approaches for assessing radical scavenging activity (RSA) in natural substrates is the DPPH technique (El-Anany et al., 2021). The antioxidant activity of GC, RC, MLLP, and binary combinations of RC and MLLP as assessed by the DPPH radical scavenging technique is shown in Table 1. DPPH radical-scavenging activities of of GC samples was found to be 74.25 %. Roasted coffee (RC) and MLLP exhibit radical-scavenging activities against DPPH with values of 67.74 and 95.19%, respectively. Unroasted ground coffee extract has the highest capability of DPPH radical scavenging (89.55%), however instant coffee extract possesses the least rate of free radical scavenging (56.16%) (Hudáková et al., 2016). The dichloromethane and methanol extracts of M. longifolia exhibited favorable antioxidant properties when measured by the 2,2 -diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability, bleaching -carotene, and prevention of linoleic acid peroxidation measurements. M. longifolia methanolic extracts exhibited the greatest IC50 value (maximum radical scavenging activity), whereas n-hexane extract had the lowest IC50 value (Iqbal et al., 2013). MLLP has approximately 1.40 times the radical-scavenging activity of roasted coffee (RC). The DPPH radical-scavenging activity of roasted coffee (RC) fortified with different quantities of MLLP ranged from 67.74 to 71.45 % (percent DPPH inhibition). The RC supplemented with 1.25% MLLP exhibited the highest antioxidant activity (71.45% inhibition of DPPH), whereas the control samples had the lowest (67.74% inhibition of DPPH). DPPH radical-scavenging activity increased significantly from 67.74% in control samples (without MLLP addition) to 69.59, 69.74, 70.32, and 71.45 (% DPPH inhibition) in RC samples enriched with 0.50%, 0.75%, 1.00%, and 1.25% MLLP, respectively.

The antioxidant and anticancer properties of molecules have been suggested to be due to the additive and synergistic effects of phytochemicals (Al-Owaisi et al., 2014; El-Anany et al., 2021). Therefore, the result showed that that the synergistic properties of combining dried Mentha longifolia leaves powder (MLLP) and roasted coffee may provide health benefits These findings suggest that the presence of phenolic and flavonoid components, which can act as reducing agents through providing electrons and interacting with free radicals to change them into more stable molecules, may be responsible for the molecule’ antioxidant activity.

3.2. Effect of incorporation various levels of MLLP into RC on some oxidative indices of coffee oil during storage

3.2.1. Acid value (AV)

The acid value is an important measure for the quality of edible oil during the storage period. The acid value is used to estimate the quantity of fatty acids released as a result of the lipolytic enzyme lipase, temperature exposure, and/or moisture absorption. The maximum acid value allowed is 4mgKOH/g oil (Codex Alimentarius Commission: Codex Stan, 1999). Figure 1 illustrates the impact of various levels of MLLP addition into RC powder on the AV of coffee oil during storage times. The initial determined AV of oil was 0.69 mg KOH/g oil at the start of the storage experiment. The AVs of tracked oils at the end of their storage duration (six months) were significantly higher than the initial AVs. The total quantity of free fatty acid generated has been showed to increase with storage length. The AVs of coffee oils enriched with different concentrations of MLLP were significantly lower at the end of the storage period when compared to the free fatty acids value of the untreated coffee sample (Figure 1). Lipid oxidation is the most crucial quality factor in food items, and it has an adverse effect on health benefits, flavor, texture, as well as overall appearance (Barden & Decker, 2016). Therefore, efforts should be implemented to reduce lipid oxidation and improve their long-term stability. MLLP addition to roasted coffee significantly decreased AVs (p 0.05) during storage times. These decreases have been developed as MLLP concentration increased. The AV of the control coffee sample (without MLLP addition) was approximately 1.34, 1.59, 1.87, and 2.08 times higher at the end of the storage time (6 months) than the AV of coffee samples coupled with 0.50, 0.75, 1.00, and 1.25% MLLP, respectively. These findings are consistent with those presented by Said et al. (2011), who demonstrated that Mentha Longifolia L significantly improved cellular viability by limiting protein and DNA damage, lowering lipid peroxidation, as well as protecting glutathione and superoxide dismutase activity throughout the shorter phases of oxidative stress induction. The aforementioned findings are congruent with the findings of El-Anany et al., 2021, who discovered that treating roasted coffee with different quantities of lemongrass leaves had a significant inhibitory effect on free fatty acid levels.

Figure 1. The impact of inclusion different amounts of MLLP into roasted coffee powder on the acid value (AV) of coffee oil during storage periods.

3.2.2. Peroxide value (PV)

Peroxide value (PV) is an effective tool to evaluate the primary lipid oxidation byproducts. Food lipid oxidation is undesirable due to the fact that it can result in the loss of fat-soluble vitamins, unpleasant flavors, as well as hazardous substances (Saadet et al., 2012). Figure 2 shows the impact of inclusion different amounts of MLLP into roasted coffee powder on PV of coffee oil during storage periods. At the beginning of the storage experiment, the oil’s peroxide value was 2.87 meq O₂/kg oil. As storage time extended, the PV of coffee oil samples increased significantly (p ≤ 0.05) (Figure 2). Lipid hydroperoxides have been discovered as main auto-oxidation products, and hydroperoxide decomposition produces secondary oxidation products such as aldehydes, ketones, hydrocarbons, volatile organic acids, and epoxy compounds. Therefore, the production of lipid hydroperoxides could explain these increases in peroxide values (El-Anany et al., 2021). By the end of the storage periods, the untreated coffee samples with no MLLP addition (control) exhibited the greatest PV value (11.00 meq O2/kg oil). Blending roasted coffee with 1.00% and 1.25% MLLP, on the other hand, achieved the lowest peroxide values (6.23 and 6.34 meq O2/kg oi). This finding could be connected to bioactive phytochemical substances in dried Mentha longifolia leaves powder that inhibit hydroperoxide formation in RC samples. When roasted coffee samples were incorporated with different quantities of MLLP, their peroxide values reduced significantly (p ≤ 0.05) during the storage times. The peroxide value of roasted coffee supplemented with 0.5%, 0.75%, 1.00%, as well as 1.25% MLLP was found to be approximately 1.20, 1.28, 1.73, and 1.76 times lower than that of non-supplemented coffee samples at the end of storage times. The reduced levels of hydroperoxides could be linked to the availability of significant quantities of phenolic compounds in MLLP, which play a crucial function in scavenging the generated free oxygen, which results in less oxidative degradation of roasted coffee. The obtained results recognize with those provided by Raeisi et al., 2015, who found that lipid oxidation and spoilage of rainbow trout fillets stored at 4°C were significantly delayed in samples subjected to wild mint (Mentha longifolia L.) leaf extract compared to control samples.

Figure 2. The impact of inclusion different amounts of MLLP into roasted coffee powder on peroxide value (PV) of coffee oil during storage periods.

3.2.3. p-anisidine value

p-anisidine value (AV) is an analytical method used to determine the extent of oxidative rancidity in lipid molecules. This technique is a good indicator about the presence of secondary oxidation products of unsaturated fatty acids (USFAs), which are predominantly conjugated dienals and 2-alkenals (El-Anany et al., 2021). Figure 3 demonstrates the effect of various quantities of MLLP addition into roasted coffee (RC) on the p-anisidine value of coffee oil during storage process. The RC’oil had a p-anisidine value of 2.45 at the beginning of the storage trial. All coffee oil samples’ p-AV increased significantly during the storage intervals (Figure 3). The increase in para anisidine (p-AV) values during storage occurs by decomposition of less stable hydro peroxides which produced at primary oxidation stage, to form secondary oxidation products (aldehydic substances) which measured by by p-AV. The control coffee oil had the highest p-anisidine value (10.00) at the final stage of the storage process. The increase in p-AVs of coffee oils incorporated with MLLP were lower than that of control coffee oil without MLLP addition (Figure 3). The incorporation of various concentrations of MLLP (0.25%-1.25%) caused significant (p ≤ 0.05) reductions in p-AV. The p-anisidine value (AV) of roasted coffee supplemented with 0.5%, 0.75%, 1.00%, and 1.25% MLLP was found to be approximately 1.25, 1.40, 1.58, and 1.63 times lower than that of non-supplemented coffee samples at the end of storage periods. The reduction in secondary oxidation generation at the final stage of the storage trail for RC samples treated with MLLP ranged from 4.30% to 39.00% when compared to control samples (without MLLP addition). These findings suggest that MLLP’s phenolic compounds have a significant inhibitory effect on the formation of secondary lipid oxidation products. These findings are consistent with the findings of Delfanian et al. (2018), who discovered that nanoencapsulated bene hull polyphenols prevented oil oxidation in W/O/W emulsions as compared to control samples.

Figure 3. The impact of inclusion different amounts of MLLP into roasted coffee powder on p-anisidine value of coffee oil during storage periods.

3.2.4. Total oxidation value

The TOTOX value provides a more realistic assessment of the oxidation progress of oil molecules, owing to the fact that primary oxidation products are either volatilized or changed into secondary oxidation byproducts (El-Anany et al., 2021). Figure 4 shows changes in the TOTOX value of RC enriched with various concentrations of MLLP during storage. The TOTOX value of roasted coffee oil was 10.64 at the beginning of storage time The Totox value of coffee oils is important to take into account as it is low during the initial storage intervals and gradually increases toward the end. TOTOX values exhibited comparable behavior to PVs. As the quantity of hydro peroxides increased correspondingly increased the Totox values, as shown in Figures 2 and 4. The untreated coffee samples (without MLLP addition) exhibited the highest Totox value (42.00) at the end of the six-month storage period. TOTOX values were significantly (p 0.05) lower in RC samples treated with various amounts of MLLP than in control coffee samples. Dried MLLP inhibited the formation of both primary and secondary oxidation products in a dose-dependent manner during storage intervals. At the end of storage intervals, the Totox value of RC enriched with 0.25, 0.50, 0.75, 1.00, and 1.25% MLLP was found to be close to 1.07, 1.22, 1.33, 1.66, and 1.70 times lower than that of untreated coffee samples. These findings are consistent with those of Bozin et al., 2007, who discovered that aromatic herbs are key providers of antioxidant substances. These findings imply that MLLP has a significant function in minimizing coffee oil oxidation through storage process.

Figure 4. The impact of inclusion different amounts of MLLP into roasted coffee powder on Totox value of coffee oil during storage periods.

Generally speaking, Lipid oxidation is the most important quality factor in foods, and it will affect the health benefits, the taste, texture, and overall appearance of food, limit the quality of lipid-containing meals, decrease the shelf life, as well as generate massive economic losses ((Barden & Decker, 2016). Hydro-peroxides start a new chain reaction when they interact with free radicals (Porter, 2013). These considerations emphasize the importance of understanding the lipid oxidation mechanism and identifying the factors which affect the oxidation reaction pathways. These primary oxidation products decompose rapidly into secondary oxidation products, which leads coffee lipids to deteriorate and turn rancid. Lipid oxidation is additionally believed to cause nutrient loss, the development of unpleasant sensory characteristics, as well as the generation of toxic by-products. Accordingly, lipid oxidation prevention is essential for enterprises interested with both health-promoting products and shelf-life-extension innovations (Félix et al., 2020). Many types of substances are known to contain natural antioxidants (mostly of the polyphenol type) and scientists have investigated the potential contributions (either as whole ingredients or as isolated extracts/compounds) in product formulations. Therefore, complex herbal extracts will have a combined inhibitory capacity for lipid peroxidation based on the antioxidants in their structure that are able to reduce oxidative stress and break the chain reaction of lipid radical propagation (Oswell et al., 2018). The increasing demand and effectiveness of natural aromatic compounds, and essential oil components provide an attractive reason to investigate mint’s biochemical and nutritional benefits. To develop this area of the raw plant market, it is important to increase the variety and biodiversity of these items (Hutsol et al., 2023). The total phenolic component levels for different Mentha species ranged from 6% to 12%, in accordance with Olennikov and Tankhaeva (2010). This suggests that phenolic components such as phenolic acids (PAs), flavonoids, as well as tannins play an important role in the biological characteristics of Mentha extracts. Freshly mint leaves possess a high biological value since they consist of a wide range of biologically active substances such as alkaloids, saponins, organic acids, vitamins, carotenoids, chlorophylls, as well as macro- and micronutrients (Al-Tawaha et al., 2013).

3.3. Sensory properties of RC enriched with various quantities of MLLP

Figure 5 shows the organoleptic properties of coffee samples incorporated with various quantities of dried Mentha longifolia leaves powder (MLLP). Freshly made coffee samples were tested for sensory properties. There were no notable differences (p ≤ 0.05) in the appearance of the control coffee sample and those coffee samples enriched with various quantities of Mentha longifolia leaves powder (MLLP) (Figure 5). This finding suggests that incorporating of Mentha longifolia leaves powder (MLLP) into coffee recipes has no effect on the appearance aspect of prepared coffee. The odor scores of the tested coffee samples varied from 7.90 to 8.75. The RC samples that were supplemented with MLLP exhibited significantly higher odor rankings (p ≤ 0.05) compared to the control coffee samples (which did not include MLLP). The greatest odor score (8.75) was obtained for coffee samples augmented with 1.25% MLLP. These samples were followed by coffee samples fortified with 1.00, 0.75, 0.50, and 0.25 MLLP (8.65, 8.60, 8.60, and 8.50, respectively). The predominant constituents of M. longifolia essential oil are monoterpenes, especially the oxygenated forms including borneol, 1,8-cineole, pulegone, menthone, isomenthone, menthol, and piperitenone oxide (Mkaddem et al., 2009). The primary component, menthol, is responsible for much of the plant’s therapeutic qualities (Gulluce et al., 2007). Consequently, Mentha finds extensive use in the food, flavoring, cosmetic, and medicinal industries (Al-Okbi et al., 2015). On the contrary, control coffee samples without MLLP addition had the lowest odour score (7.90). The coffee items were rated on the taste spectrum that ranged from 6.45 to 8.15. The coffee samples that were enriched with 0.50 and 0.75% MLLP received the best taste scores. The yogurt with a significant amount of mint won highest scores for taste and satisfaction (Bulut et al., 2021). In terms of global production, mint is now recognized as one of the most significant commercial essential oil-bearing plants, alongside the essential oils of spearmint (Mentha spicata L), peppermint (Mentha piperita L), and corn mint (Mentha arvensis L) getting the most valuable for application in culinary products, desserts, cosmetics, and pharmaceuticals (Shahi et al., 1999). Conversely, the coffee sample that was enhanced with 1.25% MLLP had the lowest taste score (6.45). Despite, all of the coffee samples had acceptance ratings that were higher than 7.79 overall. The greatest acceptance scores (8.31, 8.32) were achieved by the coffee samples that included 0.50% and 0.75% MLLP. An adverse effect was observed on the overall acceptability of the brewed coffee when 1.25% MLLP was incorporated to roasted coffee. The sensory attributes of the enriched coffee samples were unchanged at low addition levels of up to 1.00%; however, the coffee turned unpleasant at levels above 1.25% MLLP addition.

Figure 5. Sensory features of roasted coffee(RC) with various amounts of dried Mentha longifolia leaves powder (MLLP).

4. Conclusions

Total phenolic contents in dried Mentha longifolia leaves powder (MLLP) were considerable, 1.83 times higher than those in roasted coffee. The TPC of the investigated coffee samples increased significantly as the MLLP quantity increased. Comparing MLLP to roasted coffee (RC), its radical-scavenging activity is approximately 1.40 times higher. In terms of percent DPPH inhibition, the RC fortified with various amounts of MLLP exhibited DPPH radical-scavenging activity ranged from 67.74 to 71.45. While the control samples had the lowest value (67.74% inhibition of DPPH), RC supplemented with 1.25% MLLP exhibited the highest antioxidant activity (71.45%). In comparison to the control sample without MLLP addition, the acid, peroxide, P-Anisidine, and Totox values of RC supplemented with 1.25 MLLP were approximately 2.08, 1.76, 1.64, and 1.70 times lower, respectively. The greatest acceptability scores (8.31, 8.32) were achieved by the coffee samples that included 0.50% and 0.75% MLLP.

Acknowledgment

Researcher would like to thank the Deanship of Scientific Research, Qassim University for funding publication of this project

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Acknowledgment Researcher would like to thank the Deanship of Scientific Research, Qassim University for funding publication of this project .

Notes on contributors

Rehab F. M. Ali

Rehab Farouk Mohammed Ali is a Professor of Biochemistry at Faculty of Agriculture, Cairo University.In the same time she is an associate professor of biochemistry and nutritional biochemistry at the Department of Food Science and Human Nutrition, College of Agriculture and Veterinary Medicine, Qassim University, Buraydah, Saudi Arabia. Her research interest focuses on lipid chemistry, Biochemical Experiments, Antioxidant Activity of Natural Products, Bio-active compounds, functional foods, coffee products as well as extending the shelf life of food products.