Stability of Butter Using Spray Dried Sweet Lime Peel (SLP) Powder

ABSTRACT

The current study was designed to evaluate the effects of sweet lime peel powder (SLPP) on the quality and stability of butter at different storage intervals. Butter is a high-fat food containing trace amounts of water, minerals, and vitamins. Limetta Citrus Risso contains polyphenols, antioxidants, antimicrobial compounds, minerals, and vitamins. Physicochemical analysis (hunter color (L*, a*, and b*) and pH), quality tests (TBARS value and peroxide value), antioxidant activity (DPPH and total phenolic contents), microbiological analysis, and sensory evaluation of butter enriched with SLPP were performed to observe the changes on different treatments at storage intervals with vacuum and aerobic packaging. The butter was treated with 1.5%, 3%, 4.5%, and 6% sweet lime peel powder (SLPP). The variations in TBARS and POV were observed significantly in butter during different treatments, storage periods, and packaging. The results showed that color was changed significantly concerning different treatments, storage periods, and packaging. The L* and b* values were observed to be highest in aerobic packaging, whereas the a* value was increased in vacuum packaging. The antioxidants (DPPH, and TPC) varied significantly in both types of packaging on different treatments at storage intervals. High DPPH and phenolic contents were noticed in the 6% SLPP sample, while lower values were noted in the control sample. The negligible variations were analyzed in appearance, taste, color, odor, and overall acceptability.

KEYWORDS:

• Sweet lime peel powder
• butter
• packaging
• sensory parameters
• quality attributes

Introduction

Dairy products are an important part of a healthy diet that are considered nutritious food.^[1] Dairy products are one of the most chosen and widely consumed food groups. Traditional dairy products are classified as functional foods including yogurt, cream, powdered milk, kefir, condensed milk, casein, infant milk formula, ricotta, butter, ice creams, cheese, and fermented dairy drinks.^[2] Dairy products are a good source of major nutrients (protein, fat, and carbohydrate) and minor nutrients (vitamins A, vitamin B12, calcium, riboflavin, phosphorous, potassium, magnesium, zinc, and iodine). These products play an important role in improved blood pressure, immunity, and intestinal health and diabetes,^[3] and have their intrinsic nutritional qualities (energy production, antioxidants, anti-inflammatory activities, bone and tooth building, and immune-boosting).^[4] Butter is basically a pale yellow substance made by churning cream.^[5] Butter is a complex biological dairy product with modest that contained water, minerals, vitamins, and enzymes.^[6] However, butter contained saturated fats including palmitic and stearic acid that may be good for human health.^[7] It lowers the level of low-density lipoprotein (LDL) in human blood. Butter has a higher quantity of butyric acid than other short-chain fatty acids (SCFAs). Phospholipids have a wide range of biological functions critical to human health.^[8] The popularity of functional meals has exploded in recent years.^[9] Functional foods are widely acknowledged as having additional health-promoting, disease-prevention, and well-being-maintaining benefits.^[10] Functional dairy foods are widely used food ingredients including probiotics, prebiotics, mushrooms, and bioactive extracts. These functional dairy foods have various biological effects including antioxidant, cardioprotective, antihypertensive, immunomodulatory, antimicrobial, antidiabetic, anti-inflammatory, neuromodulator, and bone protection.^[11] In recent years, the scope of plant-food bioactivity has gained a lot of interest such as pharmacological effects and biotechnological applications.^[12] Citrus fruits contain bioactive compounds that can play an important role in the development of functional foods.^[13] Limetta Citrus Risso belongs to the Rutaceae family. Citrus limetta Risso is a major commercial fruit crop. It is low in calories and contains minerals (calcium, phosphorus, potassium, and iron) and vitamins (riboflavin, thiamine, niacin, and ascorbic acid).^[14] The peel of sweet lime is considered as waste that contained different types of phenolic compounds and antioxidants.^[15–17] Microbiological, physicochemical, and sensory parameters are used to evaluate the quality and shelf life of dairy products. Modified atmosphere packaging (MAP) and vacuum packaging (VP) play an important role in maintaining food shelf life of products. Combining packaging (VP and MAP) and essential oil can improve the shelf life of whey cheese while also maintaining freshness and sensory properties.^[18] The current study is designed to improve the stability of butter by enrichment of sweet lime peel powder (SLPP). For this purpose, different analysis was performed to check physicochemical attributes, microbial load, stability parameters, and sensory evaluation of SLPP-based butter on different storage at aerobic and vacuum packaging.

Material and methods

Procurement of raw material

The current study was conducted at Department of Food Science, Government College University, Faisalabad, Pakistan, and Institute of Food Science and Nutrition, Bahauddin Zakariya University, Multan, Pakistan. The butter sample was procured from Metro, Multan, Pakistan, whereas the sweet lime (Citrus limetta Risso) peel was collected from the local market, Multan, Pakistan. The butter samples were treated with sweet lime peel powder. After that, the samples were packed in a vacuum and aerobic package. The samples were stored at different intervals (0, 10, and 20 d). For this study, all chemicals and reagents were collected from Sigma Aldrich (Tokyo, Japan).

Preparation of SLPP by using spray dryer

The sweet lime peel extract was made for the purpose of the spray drying process. The high-speed blender was used to mix the gum arabic (GA) and maltodextrin (MD) in distilled water. After that, the butter was added to the mixture. Soy lecithin was added as an emulsifier and mixed by stirring for 20 min. The high-speed homogenizer was used to homogenize the solution at 10,000 rpm for 5 min. The sweet lime peel powder was obtained by spray drying the prepared liquid emulsion in a mini spray dryer. For this purpose, the spray drying was operated on different factors including the inlet air temperature (180°C), wall material (15), pump speed (7 mL/min), and needle speed (9 S).

Analysis design and treatments

Butter samples were taken and divided into different groups. The sweet lime (citrus limetta Risso) peel powder (SLPP) was mixed with butter in different concentrations as shown in Table 1.

Table 1. Treatment plan of SLPP-treated butter.

Treatment	Material (Butter %)
Control	100
1.5% SLPP	98.5
3% SLPP	97
4.5% SLPP	95.5
6% SLPP	94

SLPP, sweet lime peel powder

Storage interval

The effect of storage on butter-treated samples was measured. The butter samples were packed in a vacuum and aerobic package and kept in a refrigerator for various storage periods (0, 10, and 20 d).

Physicochemical analyses

pH

The pH of the treated butter was determined by homogenate of the sample with distilled water (1 → 10) using a digital pH meter calibrated with standard pH buffers of 4.01, 7.00, and 10.01 at 25°C. Three replicate measures were taken of each sample.

Hunter’s color

The surface color of the butter was determined via a Hunter colorimeter, with the help of standardized measurements concerning a white calibration plate (L = 89.2, a = 0.921, and b = 0.783). The CIE L* (lightness), CIE a* (redness), and CIE b* (yellowness) color values, using an average from nine random readings, were obtained on the surface of each sample for statistical readings

Quality and stability test

TBARS value

The lipid oxidation of butter was measured using the 2-thiobarbituric acid reactive substances (TBARS) method described by Ahn et al.,^[19] with a few modifications. The concentration of malonaldehyde was determined by utilizing the following formula. The estimates of TBARS were evaluated as milligram (mg) malondialdehyde per kilogram (kg) of butter:

$\mathrm{m}\mathrm{g}\mathrm{m}\mathrm{a}\mathrm{l}\mathrm{o}\mathrm{n}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{l}\mathrm{d}\mathrm{e}\mathrm{h}\mathrm{y}\mathrm{d}\mathrm{e}\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{r}\mathrm{k}\mathrm{g}\mathrm{b}\mathrm{u}\mathrm{t}\mathrm{t}\mathrm{e}\mathrm{r}=\frac{\left(\mathrm{S}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{e}\mathrm{a}\mathrm{b}\mathrm{s}\mathrm{o}\mathrm{r}\mathrm{b}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}-\mathrm{b}\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{k}\right)\times \mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{s}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{e}\mathrm{v}\mathrm{o}\mathrm{l}.}{0.000156\times 1000}$

Peroxide value

The peroxide value of designer butter was determined according to the method described by the International Dairy Federation (IDF) Koniecko,^[20] with few modifications. At 500 nm of wavelength, the absorbance of the blank was measured.

$Peroxidevalue=\frac{\left(As-Ab\right)\times m}{55.84\times \mathrm{m}0\times 2}$

where As is the absorbance of the sample; Ab = Absorbance of the blank; m (Standard) = 41.52; m0 = mass in gram; 55.84 = atomic weight of iron.

Antioxidant activity

DPPH free radical scavenging activity

The DPPH values of sweet lime peel powder (SLPP) treated butter samples were analyzed with the respected method of Brand-Williams et al.^[21] with some modifications. The samples were taken from treated butter and homogenized properly. The homogenizer was used to homogenize the sample. One-milligram sample was taken from a homogenization solution and mixed in fresh formation 0.0012 M DPPH. After that, the mixture was packed properly and kept in shadow at a suitable condition (25°C for 60 min). At 517 nm frequency, the absorbance was measured using a spectrophotometer. Each sample of butter was represented as a percentage of DPPH. The inhibition of free radicals by DPPH in percent (%) was calculated using the following equation:

$Inhibition\hspace{0.17em}\left(\mathrm{\%}\right)\hspace{0.17em}=\hspace{0.17em}100\hspace{0.17em}x\hspace{0.17em}\left(A\hspace{0.17em}blank\hspace{0.17em}-\hspace{0.17em}A\hspace{0.17em}sample/\hspace{0.17em}A\hspace{0.17em}blank\right)$

Total phenolic contents (TPCs)

The total phenolic contents of the butter sample were analyzed with the method of Folin/Ciocalteu.^[22] The 0.5 ml sample was taken and added in 10% Folin/Ciocalteu reagents (1 ml). After that, the solution was mixed properly, and the sample was kept in shadow for 6 min. The solution (2 ml of 20% NaCO₃) was added to the homogenized mixture. A standard solution of gallic acid was used to make the calibration curve. The total phenolic contents of butter samples were represented as 1 g of equivalent gallic acid per gram of sample.

Microbial quality

Samples were prepared and analyzed for total bacteria count yeast and mold at different storage intervals. The microbial counts of treated butter were measured by the guidelines of the Association of Official Agricultural Chemists (AOAC) (2005) expressed as log CFU/g. The butter samples were placed in each enrichment broth at favorable conditions. After that the samples were incubated.

Total bacterial count: The total bacterial count of treated butter was determined using the respected method of AOAC (2005). For dilution purposes, peptone water was used. One gram of butter was diluted in the tube in 9 ml of peptone water. A separate plate agar was employed as a pure culture for total plate count assessment and was cultured at 36°C for 48 h. The entire plate number had been enumerated using a comet assay.

Yeast and Mold: Yeast and mold were measured in butter samples using the respected method of AOAC (2005). For dilution purposes, peptone water was used. In the tube, 1 g of butter was digested in 9 ml of peptone water. The cell culture for yeast and mold count was measured through potato dextrose agar cultured at 25°C for 5 days. The entire plate population had been enumerated using a colony counter.

Sensory evaluation

Sensory evaluation of butter treatments was carried out by trained panelists. The nine-point hedonic scale (9 = extremely liked; 1 = extremely disliked) was used by following the guidelines of Meilgaard.^[23] During sensory evaluation, the panelists were given mineral water, unsalted crackers, and expectorant cups to neutralize and rinse their taste receptors for rational assessment. A number of panelists were selected for sensory evaluation of SLPP-treated butter.

Statistical analyses

The data for different parameters were analyzed statistically using the Statistical Package, Statistic 8.1. Levels of significance (p ≤ .05) were determined (analysis of variance, ANOVA) using a three-factor factorial under a completely randomized design (CRD) by following the principles outlined by Steel & Torrie.^[24] The means were compared using the least significant difference (LSD).

Results and discussion

Physicochemical analyses

pH

The pH range of different butter samples was found between 6.58 ± 0.05 and 6.18 ± 0.01 as mentioned in Table 2. A higher value was observed in the control sample, whereas a lower value was observed in 6% SLPP. During storage, the maximum pH level was quantified at zero-day. However, the minimum pH level was determined on the 20th day of storage. Our results rectified that the pH values of all-butter samples were recorded to reduce over storage time intervals. However, reduction in butter pH evaluated that with the passage of storage time, the butter acidity level increased.

Table 2. pH value of butter treated with sweet lime peel powder at different storage periods (0, 10^th, and 20^th days) with vacuum and aerobic packaging.

Parameter	Treatment	Storage intervals (days)
		0		10		20
		Aerobic	Vacuum	Aerobic	Vacuum	Aerobic	Vacuum
pH	Control	6.58 ± 0.05	6.54 ± 0.05	6.45 ± 0.04	6.39 ± 0.03	6.37 ± 0.03	6.29 ± 0.02
	1.5% SLPP	6.5 ± 0.04	6.47 ± 0.04	6.4 ± 0.03	6.34 ± 0.03	6.32 ± 0.03	6.24 ± 0.02
	3% SLPP	6.46 ± 0.04	6.42 ± 0.04	6.37 ± 0.03	6.31 ± 0.03	6.29 ± 0.02	6.21 ± 0.02
	4.5% SLPP	6.4 ± 0.03	6.38 ± 0.03	6.31 ± 0.03	6.25 ± 0.02	6.23 ± 0.02	6.15 ± 0.01
	6% SLPP	6.35 ± 0.03	6.32 ± 0.03	6.28 ± 0.02	6.22 ± 0.02	6.18 ± 0.01	6.1 ± 0.01
	Mean	6.46 ± 0.04a	6.43 ± 0.04a	6.36 ± 0.03b	6.3 ± 0.02b	6.28 ± 0.02c	6.2 ± 0.01c

SLPP, sweet lime peel powder. The values are the mean ±SD of three independent determinations. Means carrying different letters in rows differed significantly

On different treatments, an extreme pH value of SLPP-treated butter was found in the control sample, while the least pH value of SLPP-treated butter was detected at 6% SLPP. Our findings showed that the pH value decrease with the increase in the concentration of SLPP. In aerobic packaging, the higher pH value was 6.58 ± 0.05 and the lower pH value was 6.18 ± 0.01. The extreme value was observed in the control sample, whereas the lower value was observed in the 6% SLPP sample. The higher value was observed at 0-day storage, while the lower value was observed at 20thday storage.

In vacuum packaging, the higher pH value was 6.58 ± 0.05 and the lower pH value was 6.10 ± 0.01. The extreme value was observed in the control sample, whereas the lower value was observed in the 6% SLPP sample. The higher value was observed at 0-day storage, while the lower value was observed at 20th day storage. The current study is in accordance with a study in which plant extract was used to create value-added butter by Thakaeng et al.,^[25] who concluded that green tea butter had significantly more acid value. Furthermore, this work is in corroboration with Ozkan et al.,^[26] who conducted the research by adding essential plant oil in butter and concluded that titratable acidity and a number of viable lactic acid bacteria were compared to the control and determined higher during the storage time. The plant residue is composed of different phytochemicals (phenolic compounds and antioxidants). These different compounds have the ability to reduce the oxidation process. However, reduction in oxidation can reduce the pH.

Hunter color

L value

The L (Lightness) value of treated butter samples ranged from 137 ± 8 to 148 ± 14. The control sample had a higher value, whereas the 6% SLPP sample had a lower value. At zero-day, the maximum L value was measured during storage. On the 20th day of storage, the minimum L value was determined. Our findings revealed that the L value of all-butter samples decreased with the passage of storage intervals. The control sample had the highest L value of SLPP-treated butter, while the lowest L value of SLPP-treated butter was detected at 6% SLPP. The L value decreased with the concentration of SLPP as mentioned in Table 3.

Table 3. Hunter’s color of butter after treated with sweet lime peel powder at different storage periods (0, 10^th, and 20^th days) with vacuum and aerobic packaging.

Parameter	Treatment	Storage intervals (days)
		0		10		20
		Aerobic	Vacuum	Aerobic	Vacuum	Aerobic	Vacuum
L	Control	148 ± 14	146 ± 13	147.35 ± 14	145 ± 13	146 ± 13	144 ± 13
	1.5% SLPP	146 ± 13	144 ± 12	145 ± 12	143 ± 10	145 ± 13	142 ± 11
	3% SLPP	145 ± 13	143 ± 10	145 ± 12	143 ± 10	143 ± 12	141 ± 11
	4.5% SLPP	143 ± 11	141 ± 11	141 ± 11	139 ± 9	141 ± 10	138 ± 7
	6% SLPP	142 ± 11	140 ± 10	140 ± 10	139 ± 8	140 ± 9	137 ± 8
	Mean	145 ± 12a	142 ± 11a	143 ± 12b	142 ± 10b	143 ± 1c	14010c
a	Control	4.88 ± 0.3	5.50 ± 0.4	4.10 ± 0.2	5.08 ± 0.3	3.89 ± 0.2	4.72 ± 0.3
	1.5% SLPP	5.50 ± 0.4	6.35 ± 0.5	4.72 ± 0.4	5.66 ± 0.4	4.00 ± 0.2	5.01 ± 0.3
	3% SLPP	5.71 ± 0.4	6.67 ± 0.6	4.93 ± 0.4	5.88 ± 0.5	4.21 ± 0.2	5.31 ± 0.4
	4.5% SLPP	5.98 ± 0.5	6.89 ± 0.6	5.20 ± 0.4	5.99 ± 0.5	4.48 ± 0.2	5.62 ± 0.4
	6% SLPP	6.38 ± 0.6	7.01 ± 0.6	5.60 ± 0.4	6.20 ± 0.5	4.88 ± 0.3	5.91 ± 0.5
	Mean	5.69 ± 0.4a	6.48 ± 0.4a	4.91 ± 0.5b	5.76 ± 0.5b	4.29 ± 0.3c	5.31 ± 0.5c
b	Control	54 ± 5	52 ± 4	53 ± 5	52 ± 4	53 ± 5	51 ± 4
	1.5% SLPP	52 ± 5	51 ± 3	52 ± 4	50 ± 3	52 ± 5	50 ± 4
	3% SLPP	51 ± 4	50 ± 3	51 ± 4	49 ± 3	51 ± 4	49 ± 3
	4.5% SLPP	50 ± 3	48 ± 3	49 ± 3	48 ± 2	50 ± 3	48 ± 2
	6% SLPP	49 ± 3	47 ± 2	49 ± 3	47 ± 1	49 ± 3	47 ± 1
	Mean	51 ± 4a	49 ± 3a	51 ± 4b	49 ± 3b	51 ± 4c	49 ± 3c

SLPP, sweet lime peel powder. The values are the mean ±SD of three independent determinations. Means carrying different letters in rows differed significantly.

The higher L value in aerobic packaging was 148 ± 14, while the lower L value was 139 ± 9. The control sample yielded the highest value, while the 6% SLPP sample yielded the lowest value. The higher value was found at 0 days of storage, and the lower value was found at 20 days. The higher L value in vacuum packaging was 146 ± 13, while the lower L value was 137 ± 8. The control sample yielded the highest value, while the 6% SLPP sample yielded the lowest value. The higher value was found at 0 days of storage, and the lower value was found at 20 days. The color of SLPP-treated butter can be changed due to different phenolic compounds and powder color. According to the research of Thakaeng et al.,^[25] the amount of green tea extract caused a decrease in the lightness value of the butter sample. A recent study on oregano essential oil as an antioxidant in functional dairy beverages showed that lightness of the dairy beverages (L value) decreased with increasing OE concentration.^[27]

a value

The a value ranging from 3.89 ± 0.2 to 7.01 ± 0.6. The control sample had a higher value, while the 6% SLPP-treated sample was noted to be lower a value. During storage, the maximum a value was measured at zero-day. The minimum a value was determined on the 20th day of storage. According to our findings, the a value of all-butter samples decreased with the passage of storage intervals. The lowest a value of SLPP-treated butter was detected in the control sample, while the highest a value of SLPP-treated butter was detected at 6% SLPP. According to our findings, the a value increased with the increase in the concentration of SLPP.

In aerobic packaging, the higher a value was 6.38 ± 0.6, while the lower a value was 3.89 ± 0.2. The highest value was detected on 6% SLPP, while the lowest value was noted in control. The higher value was discovered at 0 days of storage, while the lower value was discovered at 20 days. In vacuum packaging, the higher a value was 7.01 ± 0.6, while the lower a value was 4.72 ± 0.3. The minimum outcome was seen in control sample, while the highest a value in 6% SLPP-treated sample. The higher value was discovered at 0 days of storage, while the lower value was discovered at 20 days as shown in Table 3. The redness (a) value of the butter sample increased when the amount of plant extract in butter was increased.^[25] The current study matched the results of Boroski et al.,^[27] who evaluated the same results of a using plant essential oil in the functional dairy beverage. The outcome observed was that the redness of the dairy beverages increased with increasing EO concentration.

b value

The b value of treated butter range from 47 ± 1 to 54 ± 5. The control sample had a higher value. Whereas the 6% SLPP-treated sample had a lower value. During storage, the maximum b value was measured at 0 day. However, at 20th day of storage, the minimum b value was determined. According to our findings, the b value of all samples decreased with passage of storage time. The control sample had the highest b value, whereas the lowest b value of butter was found on 6% SLPP. According to our findings, the b value decreased with the increase in the concentration of SLPP.

The higher b value in aerobic packaging was 54 ± 5, whereas the lower b* value was 49 ± 3. The lower value was evaluated on 6% SLPP, while the control sample had more value as compare to treated sample. The higher b value in vacuum packaging was 52 ± 4, while the lower b value was 47 ± 1. The control sample had the highest value, while the 6% SLPP sample had the lowest. The higher value was discovered at 0 days of storage, and the lower value was measured at 20 days as shown in Table 3. The study by Thakaeng et al.^[25] also indicated that the yellowness b value of the butter sample significantly decreased when the amount of green tea extract was increased.

Stability parameters

Peroxide value

The peroxide value (POV) range of different treated butter was determined from 0.30 ± 0.01 to 1.20 ± 0.05 as shown in Table 4. The lower POV was found on 6% SLPP, whereas the higher POV was seen in the control sample. Furthermore, POV was measured maximum at 20th day of storage. At 0 day, minimum POV was used to determine. Our findings revealed that POV of all samples increased with increase in storage intervals. On different treatments, the control sample had the highest POV, whereas the lowest POV was noted on 6% SLPP. According to our findings, POV value drops when the concentration of SLPP rises.

Table 4. POV and TBARS values of butter treated with sweet lime peel powder at different storage periods (0, 10^th, and 20^th days) with vacuum and aerobic packaging.

Parameter	Treatment	Storage intervals (days)
		0		10		20
		Aerobic	Vacuum	Aerobic	Vacuum	Aerobic	Vacuum
Peroxide value (POV)	Control	0.80 ± 0.04	0.77 ± 0.03	0.89 ± 0.05	0.85 ± 0.04	1.20 ± 0.05	1.17 ± 0.05
	1.5% SLPP	0.69 ± 0.02	0.67 ± 0.02	0.78 ± 0.03	0.76 ± 0.03	1.00 ± 0.05	1.14 ± 0.05
	3% SLPP	0.58 ± 0.01	0.55 ± 0.01	0.67 ± 0.02	0.64 ± 0.02	0.88 ± 0.05	0.85 ± 0.04
	4.5% SLPP	0.49 ± 0.01	0.46 ± 0.01	0.60 ± 0.02	0.56 ± 0.01	0.82 ± 0.04	0.78 ± 0.03
	6% SLPP	0.32 ± 0.01	0.30 ± 0.01	0.40 ± 0.01	0.39 ± 0.01	0.61 ± 0.02	0.59 ± 0.01
	Mean	0.58 ± 0.02c	0.55 ± 0.01c	0.67 ± 0.03b	0.64 ± 0.03b	0.90 ± 0.04a	0.91 ± 0.04a
TBARS	Control	0.35 ± 0.06	0.32 ± 0.04	0.41 ± 0.08	0.37 ± 0.07	0.48 ± 0.08	0.44 ± 0.08
	1.5% SLPP	0.31 ± 0.04	0.28 ± 0.02	0.38 ± 0.07	0.34 ± 0.05	0.45 ± 0.08	0.41 ± 0.08
	3% SLPP	0.27 ± 0.03	0.24 ± 0.01	0.33 ± 0.05	0.29 ± 0.03	0.40 ± 0.08	0.36 ± 0.06
	4.5% SLPP	0.25 ± 0.02	0.22 ± 0.01	0.30 ± 0.04	0.26 ± 0.02	0.37 ± 0.07	0.33 ± 0.05
	6% SLPP	0.21 ± 0.01	0.18 ± 0.01	0.26 ± 0.02	0.22 ± 0.01	0.33 ± 0.05	0.29 ± 0.03
	Mean	0.28 ± 0.02c	0.25 ± 0.02c	0.34 ± 0.05b	0.30 ± 0.04b	0.41 ± 0.06a	0.37 ± 0.05a

SLPP, sweet lime peel powder. The values are mean ±SD of three independent determinations. Means carrying different letters in rows differed significantly

The higher POV in aerobic packing was 1.20 ± 0.05, whereas the lower POV was 0.32 ± 0.01. The control sample had the highest peroxide value, while the 6% SLPP-treated sample had the lowest POV. The lower value was found at 0 days of storage, while the larger value was found at 20 days. The greater POV value in vacuum packaging was 1.17 ± 0.05, while the lower POV value was 0.30 ± 0.01. The control sample had the highest value, while the 6% SLPP sample had the lowest. The lower value was found at 0 days of storage, while the higher value was found at 20 days of storage. The SLPP is composed of different types of phenolic compounds and antioxidants. However, the oxidation process is started with the passage of time that can reduce the shelf of butter. SLPP can reduce the oxidation process because it contains lot of antioxidants. The current result for the peroxide value of butter fortified with SLPP was in collaboration with the conclusion of Manjunatha et al.^[28] who reported that the peroxide value of ghee samples increased with time by adding orange peel powder due to antioxidant potential. Our findings also matched those of Rasarathinam,^[29] who found that adding Citrus (Citrus Sphaerocarpa) Peel Extract to butter reduced the peroxide value and free fatty acid content of the butter. However, citrus peel extract can be used to make an antioxidant-rich butter. The research carried out by Thakaeng et al.^[25] also proved that the control butter has less peroxide value as compared to the green tea powder fortified butter.

TBARS value

TBARS value of various butter samples ranged from 0.18 ± 0.01 to 0.48 ± 0.08 as shown in Table 4. The higher value was found on 6% SLPP as compared to the control sample. The TBARS value was determined to be maximum at 20th day of storage. The minimal TBARS value was calculated using 0 day storage. According to our findings, the TBARS value of all-butter samples increased with storage intervals passed. The control sample of SLPP-treated butter had the highest TBARS value, while the lowest TBARS value of SLPP-treated butter was discovered on 6% SLPP. According to our findings, the TBARS value decreases with the increase in the concentration of SLPP.

In aerobic packing, the higher TBARS value was 0.48 ± 0.08, while the lower TBARS value was 0.21 ± 0.01. The highest value was found in the control sample, while the lowest was found in the 6% SLPP sample. The lower value was discovered at 0 days of storage, while the higher value was discovered at 20 days. In vacuum packaging, the higher TBARS value was 0.44 ± 0.08, while the lower TBARS value was 0.18 ± 0.01. The highest value was found in the control sample, while the lowest was found in the 6% SLPP sample. The lower value was discovered at 0 days of storage, while the higher value was discovered at 20 days.

Current findings agreed with Asha et al.^[30] who suggested that adding orange peel powder to ghee decreased the thiobarbituric acid (TBA) value. It is proved that orange peel powder can help to reduce oxidative deterioration in ghee because it contains natural antioxidants. The study conducted by Gramza-Michalowska et al.^[31] also indicated that tea extract in butter has strong antioxidant activity and played a role in butter oxidative stability improvement. Ramadan et al.^[32] conducted a study to assess the antioxidant and antimicrobial effects of carob, green, and black tea extracts on buffalo butter. According to the study findings, natural extracts (particularly green tea extracts) contain antimicrobial and antioxidant compounds (phenolic). However, antioxidants can be used as food preservatives. Antioxidants work well to increase safety and extend their shelf life while being stored without degrading their quality.

Antioxidant potential

DPPH value

The DPPH value of different butter samples was ranged from 4.17 ± 0.2 to 15.09 ± 0.5 as mentioned in Table 5. The DPPH value was greater in the 6% SLPP sample and lower in the control sample. At 20th day of storage, the minimum DPPH was measured. The maximum DPPH was calculated at 0 day storage. According to our findings, the DPPH value of all-butter samples declined with the passage storage intervals. The lowest DPPH value was noted in the control sample, whereas the highest DPPH value was found in SLPP-treated butter (6% SLPP). According to our observations, the DPPH value increases with the increase in the concentration of SLPP.

Table 5. DPPH and TPC value of butter treated with sweet lime peel powder at different storage periods (0, 10^th, and 20^th days) with vacuum and aerobic packaging.

Parameter	Treatment	Storage intervals (days)
		0		10		20
		Aerobic	Vacuum	Aerobic	Vacuum	Aerobic	Vacuum
DPPH	Control	7.11 ± 0.2	8.01 ± 0.3	6.81 ± 0.3	7.76 ± 0.4	5.99 ± 0.2	6.64 ± 0.2
	1.5% SLPP	8.21 ± 0.3	10.12 ± 0.4	6.19 ± 0.3	7.24 ± 0.3	4.17 ± 0.2	5.13 ± 0.2
	3% SLPP	9.41 ± 0.4	11.12 ± 0.4	7.39 ± 0.3	8.96 ± 0.3	6.21 ± 0.3	7.65 ± 0.3
	4.5% SLPP	11.71 ± 0.4	13.75 ± 0.5	9.68 ± 0.4	10.73 ± 0.4	7.33 ± 0.3	8.87 ± 0.3
	6% SLPP	13.31 ± 0.5	15.09 ± 0.5	10.20 ± 0.4	11.25 ± 0.4	8.93 ± 0.3	10.21 ± 0.4
	Mean	10.66 ± 0.4a	12.52 ± 0.5a	8.36 ± 0.3b	7.98 ± 0.3b	7.23 ± 0.3c	6.98 ± 0.2c
TPCs	Control	0.02 ± 0.0	0.02 ± 0.0	0.01 ± 0.0	0.01 ± 0.0	0.01 ± 0.0	0.01 ± 0.0
	1.5% SLPP	0.08 ± 0.1	0.09 ± 0.1	0.06 ± 0.0	0.07 ± 0.1	0.04 ± 0.0	0.05 ± 0.0
	3% SLPP	0.09 ± 0.1	0.10 ± 0.1	0.07 ± 0.1	0.08 ± 0.1	0.05 ± 0.0	0.07 ± 0.1
	4.5% SLPP	0.10 ± 0.1	0.12 ± 0.1	0.09 ± 0.1	0.11 ± 0.1	0.08 ± 0.1	0.10 ± 0.1
	6% SLPP	0.11 ± 0.1	0.13 ± 0.1	0.10 ± 0.1	0.12 ± 0.1	0.09 ± 0.1	0.11 ± 0.1
	Mean	0.08 ± 0.1a	0.092 ± 0.01a	0.07 ± 0.01b	0.078 ± 0.0b	0.054 ± 0.0c	0.068 ± 0.01c

SLPP, sweet lime peel powder; ND, not detected. The values are mean ±SD of three independent determinations. Means carrying different letters in rows differed significantly.

In aerobic packing, the lower DPPH was 4.17 ± 0.2, whereas the higher DPPH was 13.31 ± 0.5. The highest value was found in the 6% SLPP sample as compared to control. The smaller value was found at 20 days of storage, while the higher value was noted at 0 days. In vacuum packaging, the higher DPPH value was 15.09 ± 0.5, whereas the lower DPPH value was 5.13 ± 0.2. The smaller value was measured at 20 days of storage, while the higher value was detected at 0 days.

The current findings are in collaboration with Vidanagamage et al.,^[33] who investigated the effects of Cinnamon extract on the functional properties of butter. Furthermore, adding cinnamon to butter revealed that it contains antioxidant activity. The antioxidant activities of orange peel extract in ghee stored at different storage temperatures was demonstrated by Asha.^[30] Ghee infused with orange peel extract (OPE) had higher DPPH radical quenching activity and less FFA development. According to the findings, orange peel may be a good natural source of antioxidants that can be used to prevent oxidative deterioration in fat-rich foods like ghee. The current research findings are also similar to Hailemariam and Emire.^[34] who carried out the research by adding thyme to butter. The results concluded that thymus schimperi is a potential herb with antioxidant activity and a preservative effect that can be used as a source of antioxidants for the production of shelf-stable food products.

Total phenolic contents

The total phenolic contents of various butter samples ranged from 0.01 ± 0.0 to 0.13 ± 0.1. The 6% SLPP sample had a higher value, while the control sample had a lower number as shown in Table 5. The minimum phenolic contents were measured at 20th day of storage. At 0 day of storage, the maximum value was found. According to our findings, the total phenolic contents value decreased with the passage of intervals. The lowest total phenolic contents was found in the control sample, whereas the maximum total phenolic contents was found on 6% SLPP. According to our findings, the total phenolic contents value increases with the increase in the concentration of SLPP.

The lower total phenolic contents in aerobic packing were 0.01 ± 0.0, while the greater total phenolic contents were 0.11 ± 0.1. The greater value was noted on 6% SLPP, whereas the lower value was found on the control sample. The lower value was found after 20 days of storage, whereas the larger value was found after 0 days. The greater total phenolic contents value in vacuum packaging was 0.13 ± 0.1, while the lower total was 0.01 ± 0.0. The control sample had the lowest value, while the highest value was found on 6% SLPP. The lower value was found after 20 days of storage, whereas the larger value was found after 0 days as shown in Table 5.

The current findings are close to the results of Vidanagamage et al.,^[33] who observed that TPC increased by adding cinnamon to butter. Furthermore, adding cinnamon to butter revealed that it contains antioxidant activity. Our results are similar to Sakanaka et al.,^[35] who indicated that persimmon leaf tea is high in phenolic contents that has potent antioxidant properties, and effectively scavenges free radicals. These findings suggest that consumers may experience health advantages by fortification of persimmon leaf tea in food. The results are matched with the results of Gramza-Michalowska et al.,^[31] who examined the strong antioxidant activity by adding plant extracts in lipid.

Microbial determination

Total bacterial count

The total bacterial count of various butter samples ranged from 1.39 ± 0.05 to 4.87 ± 0.09. On 6% SLPP sample had a lower value and the control sample had a higher value as shown in Table 6. The total bacterial count was determined to be maximum on the 20th day of storage. The minimum total bacterial count was calculated at zero-day storage. According to our outcomes, the total bacterial count of all-butter samples increases with storage intervals. The control sample had the highest total plate count, while SLPP-treated butter was found to have lower total bacterial count. The total plate count value decreases with the increase in the concentration of SLPP (Table 6).

Table 6. TBC, yeast, and mold value of butter treated with sweet lime peel powder at different storage periods (0, 10^th, and 20^th days) with vacuum and aerobic packaging.

Parameter	Treatment	Storage intervals (days)
		0		10		20
		Aerobic	Vacuum	Aerobic	Vacuum	Aerobic	Vacuum
TBC (log CFU/g)	Control	2.69 ± 0.07	2.19 ± 0.06	4.47 ± 0.09	4.03 ± 0.09	4.87 ± 0.09	4.52 ± 0.09
	1.5% SLPP	2.28 ± 0.07	1.88 ± 0.06	2.80 ± 0.07	2.41 ± 0.07	3.90 ± 0.08	3.49 ± 0.08
	3% SLPP	2.09 ± 0.06	1.67 ± 0.06	2.29 ± 0.07	1.92 ± 0.06	2.79 ± 0.07	2.35 ± 0.06
	4.5% SLPP	1.89 ± 0.06	1.51 ± 0.06	2.15 ± 0.06	1.75 ± 0.06	2.37 ± 0.07	1.98 ± 0.06
	6% SLPP	1.78 ± 0.06	1.41 ± 0.06	1.88 ± 0.05	1.39 ± 0.05	2.13 ± 0.06	1.76 ± 0.06
	Mean	2.15 ± 0.07c	1.73 ± 0.06c	2.72 ± 0.08b	2.30 ± 0.07b	3.21 ± 0.09a	2.82 ± 0.08a
Yeast and Mold (log CFU/g)	Control	7.81 ± 0.09	7.73 ± 0.08	8.74 ± 0.09	8.68 ± 0.09	9.01 ± 0.09	8.94 ± 0.09
	1.5% SLPP	6.10 ± 0.07	6.03 ± 0.07	7.05 ± 0.08	6.99 ± 0.08	7.95 ± 0.09	7.90 ± 0.09
	3% SLPP	5.26 ± 0.06	5.20 ± 0.06	6.09 ± 0.07	6.04 ± 0.07	7.24 ± 0.08	7.18 ± 0.08
	4.5% SLPP	4.15 ± 0.05	4.10 ± 0.05	4.89 ± 0.06	4.83 ± 0.06	5.79 ± 0.07	5.74 ± 0.07
	6% SLPP	3.01 ± 0.05	2.94 ± 0.04	3.78 ± 0.05	3.71 ± 0.05	4.53 ± 0.06	4.47 ± 0.06
	Mean	5.27 ± 0.06c	5.20 ± 0.06c	6.11 ± 0.07b	6.05 ± 0.07b	6.91 ± 0.08a	6.85 ± 0.08a

SLPP, sweet lime peel powder. The values are mean ±SD of three independent determinations. Means carrying different letters in rows differed significantly.

In aerobic packing, the lower bacterial plate count was 1.78 ± 0.06, while the higher was 4.87 ± 0.09. The higher value was found in the control sample, while the lower value was found on 6% SLPP. After 20 days of storage, the higher value was found, while the lower value was discovered at 0 days. In vacuum packaging, the higher bacterial plate count was 4.52 ± 0.09, while the lower total bacterial count was 1.41 ± 0.06. After 20 days of storage, the higher value was found, while the lower value was discovered at 0 days.

Our results agree with Vidanagamage et al.^[33] who proved the effects of plant extract on the functional properties of butter and concluded that cinnamon butter has a low microbial count when compared to other butter due to cinnamon’s antimicrobial activity. However, results showed that both chemical and microbiological characterizations of the cinnamon butter is within acceptable standards. Another findings matched the results of Rasarathinam,^[29] who researched chemical and sensory evaluation of butter incorporated with the antioxidant extract of citrus (Citrus Sphaerocarpa) peel. Results showed that adding of citrus peel extract to butter reduced the microbial count of the butter. After specified storage, butter fortified with plant extract has a lower total plate count than butter without it, and these findings are similar to Thakaeng et al..^[25]

Yeast and mold (log CFU/g)

The yeast and mold levels in various butter samples ranged from 2.94 ± 0.04 to 9.01 ± 0.09. On 6% SLPP-treated sample had the lowest value, whereas the control sample had the highest value as mentioned in Table 7. On the 20th day of storage, the higher yeast and mold were determined. At 0 day, the minimum yeast and mold were calculated. According to our findings, the yeast and mold of all-butter samples increase with the passage of time. The control sample had the highest yeast and mold, while 6% SLPP-treated butter had the lowest yeast and mold. The current outcomes showed that the yeast and mold value decreases with the increase in the concentration of SLPP.

Table 7. Sensory evaluation (appearance, color, taste, odor, and overall acceptability) value of butter treated with sweet lime peel powder at different storage periods (0, 10^th, and 20^th days) with vacuum and aerobic packaging.

Parameter	Treatment	Storage intervals (days)
		0		10		20
		Aerobic	Vacuum	Aerobic	Vacuum	Aerobic	Vacuum
Appearance	Control	6.86 ± 0.06	6.89 ± 0.07	6.79 ± 0.08	6.81 ± 0.09	6.74 ± 0.08	6.75 ± 0.08
	1.5% SLPP	6.65 ± 0.09	6.67 ± 0.07	6.61 ± 0.07	6.63 ± 0.07	6.58 ± 0.06	6.6 ± 0.07
	3% SLPP	6.61 ± 0.07	6.63 ± 0.07	6.57 ± 0.06	6.6 ± 0.07	6.53 ± 0.06	6.57 ± 0.06
	4.5% SLPP	6.6 ± 0.07	6.61 ± 0.07	6.56 ± 0.06	6.59 ± 0.06	6.51 ± 0.06	6.56 ± 0.06
	6% SLPP	6.59 ± 0.07	6.62 ± 0.07	6.55 ± 0.06	6.58 ± 0.06	6.50 ± 0.06	6.52 ± 0.06
	Mean	6.66 ± 0.07a	6.68 ± 0.07a	6.62 ± 0.06b	6.64 ± 0.06b	6.57 ± 0.06c	6.6 ± 0.06c
Color	Control	6.9 ± 0.08	6.93 ± 0.09	6.85 ± 0.08	6.87 ± 0.08	6.80 ± 0.08	6.82 ± 0.08
	1.5% SLPP	7.02 ± 0.09	7.04 ± 0.09	6.98 ± 0.07	7.01 ± 0.07	6.82 ± 0.07	6.87 ± 0.07
	3% SLPP	7.07 ± 0.09	7.09 ± 0.09	7.04 ± 0.09	7.07 ± 0.09	6.89 ± 0.07	6.91 ± 0.07
	4.5% SLPP	7.12 ± 0.09	7.15 ± 0.09	7.07 ± 0.09	7.09 ± 0.09	7.01 ± 0.09	7.04 ± 0.09
	6% SLPP	7.18 ± 0.09	7.21 ± 0.09	7.13 ± 0.09	7.16 ± 0.09	7.09 ± 0.09	7.11 ± 0.09
	Mean	7.06 ± 0.09a	7.08 ± 0.09a	7.01 ± 0.08b	7.04 ± 0.08b	6.92 ± 0.06c	6.95 ± 0.06c
Taste	Control	6.61 ± 0.05	6.64 ± 0.06	6.57 ± 0.05	6.6 ± 0.05	6.53 ± 0.05	6.55 ± 0.05
	1.5% SLPP	6.71 ± 0.06	6.73 ± 0.07	6.67 ± 0.06	6.69 ± 0.06	6.64 ± 0.06	6.65 ± 0.06
	3% SLPP	6.78 ± 0.07	6.81 ± 0.08	6.73 ± 0.07	6.76 ± 0.07	6.69 ± 0.06	6.72 ± 0.07
	4.5% SLPP	6.88 ± 0.08	6.9 ± 0.09	6.85 ± 0.08	6.87 ± 0.08	6.82 ± 0.08	6.84 ± 0.08
	6% SLPP	6.96 ± 0.09	6.97 ± 0.09	6.95 ± 0.09	6.98 ± 0.09	6.9 ± 0.09	6.91 ± 0.09
	Mean	6.79 ± 0.06a	6.81 ± 0.07a	6.75 ± 0.07b	6.78 ± 0.08b	6.72 ± 0.06c	6.73 ± 0.07c
Odor	Control	6 ± 0.06	6.03 ± 0.06	6.07 ± 0.06	6.08 ± 0.06	6.09 ± 0.05	6.09 ± 0.06
	1.5% SLPP	6.01 ± 0.07	6.04 ± 0.07	6.06 ± 0.07	6.07 ± 0.07	6.07 ± 0.07	6.08 ± 0.07
	3% SLPP	6.04 ± 0.08	6.06 ± 0.08	6.01 ± 0.08	6.03 ± 0.08	6.06 ± 0.08	6.07 ± 0.08
	4.5% SLPP	6.23 ± 0.09	6.26 ± 0.09	6.18 ± 0.08	6.21 ± 0.09	6.15 ± 0.08	6.18 ± 0.08
	6% SLPP	6.41 ± 0.09	6.42 ± 0.09	6.37 ± 0.09	6.38 ± 0.09	6.33 ± 0.09	6.35 ± 0.09
	Mean	6.14 ± 0.08a	6.16 ± 0.08a	6.14 ± 0.07a	6.15 ± 0.07b	6.14 ± 0.06a	6.15 ± 0.07b
OA	Control	6.81 ± 0.09	6.84 ± 0.09	6.76 ± 0.08	6.79 ± 0.09	6.70 ± 0.06	6.71 ± 0.06
	1.5% SLPP	6.79 ± 0.09	6.82 ± 0.09	6.75 ± 0.08	6.77 ± 0.08	6.68 ± 0.06	6.69 ± 0.06
	3% SLPP	6.78 ± 0.09	6.80 ± 0.09	6.73 ± 0.07	6.74 ± 0.07	6.66 ± 0.05	6.67 ± 0.05
	4.5% SLPP	6.77 ± 0.08	6.78 ± 0.09	6.71 ± 0.06	6.72 ± 0.07	6.63 ± 0.04	6.65 ± 0.05
	6% SLPP	6.72 ± 0.07	6.75 ± 0.08	6.68 ± 0.06	6.70 ± 0.06	6.6 ± 0.04	6.62 ± 0.04
	Mean	6.77 ± 0.08a	6.80 ± 0.09a	6.73 ± 0.07b	6.74 ± 0.07b	6.65 ± 0.06c	6.67 ± 0.06c

SLPP, sweet lime peel powder. The values are mean ±SD of three independent determinations. Means carrying different letters in rows differed significantly.

The lower yeast and mold in aerobic packing were 3.01 ± 0.05, while the higher yeast and mold was 9.01 ± 0.09. In the control sample, yeast and mold value was calculated to be high as compared to treated sample value. During storage, the higher value was calculated at 20th day of storage, while the lower value was measured at 0 day. The higher yeast and mold in vacuum packaging was 8.94 ± 0.09, while the lower yeast and mold was 2.94 ± 0.04. The control sample had the highest value, while the 6% SLPP had the lowest. The higher value was discovered at 20 days of storage, while the lower value was discovered at 0 day.

Current outcomes are in collaboration with a study by Vidanagamage et al.,^[33] who revealed that yeast and mold were found to be undetectable (ND) in cinnamon-added samples throughout the storage period. Thakaeng et al.^[25] found that butter fortified with green tea powder has a lower yeast and mold count than control butter. Manafi et al.^[36] carried out research to observe the effects of olive leaf extract on the microbiological properties of butter and concluded that phenolic contents of olive leaf extract are useful to prevent microbial spoilage and enhance the shelf life of butter.

Sensory evaluation

Appearance

The appearance of various butter samples ranged from 6.50 ± 0.06 to 6.86 ± 0.06. However, the lower value was found on 6% SLPP, whereas the highest value was noted in the control sample. At 0, 10, and 20 days, the appearance parameter in the control aerobic butter sample was 6.86 ± 0.06, 6.79 ± 0.08, and 6.74 ± 0.08, respectively. The lower appearance value was discovered on the 20th day of storage. The higher appearance value was calculated at zero-day storage. According to our findings, the appearance value of all-butter samples decreases with passage of storage intervals. The maximum appearance score was found in the control sample, while the minimum appearance score was calculated on 6% SLPP-treated butter. The appearance score value decreases with the increase in the concentration of SLPP, as mentioned in Table 7.

In aerobic packing, the lower appearance score was 6.50 ± 0.06, while the higher appearance score was 6.86 ± 0.06. The maximum value was noted in the control sample as compared to the SLPP-treated sample. In vacuum packaging, the higher appearance score was 6.89 ± 0.07, while the lower appearance score was 6.52 ± 0.06. The highest value was found in the control sample, while the lowest score was found in the 6% SLPP sample. Current results agree with Rasarathinam,^[29] who reported that citrus (Citrus Sphaerocarpa) peel extract can be incorporated into the butter formulation without altering the appearance attributes.

Color

The color values of various butter samples ranged from 6.80 ± 0.08 to 7.21 ± 0.09. On the 20th day of storage, the lower color value was discovered. At zero-day of storage, the higher color was calculated. According to our findings, the color value of all-butter samples decreases with the passage of time. The control sample had the lowest color value, while the 6% SLPP-treated butter had the highest color.

The lower color value in aerobic packing was 6.80 ± 0.08, while the higher color score was 7.18 ± 0.09. The control sample had the lowest value, while the 6% SLPP sample had the highest value. The lower value was noted at 20 days of storage, while the higher value was noted at 0 days. The higher color value in vacuum packaging was 7.21 ± 0.09, while the lower was 6.82 ± 0.08. The lower value was noted at 20 days of storage, while the higher value was measured at 0 days as shown in Table 7. Current findings are similar to those of Nadeem et al.,^[37] who concluded that the color of treated samples was not significantly different from the control. Rasarathinam’s^[29] findings predicted that citrus peel extract can be incorporated into butter formulations without affecting color attributes.

Taste

The taste values of different butter samples ranged from 6.53 ± 0.05 to 6.98 ± 0.09. The higher value was noted on 6% SLPP, and the lower value was detected on the control sample. The lower taste was noted at 20th day of storage. The higher taste was calculated at zero-day storage. The taste value of all-butter samples was found to decrease with storage interval.

In aerobic packing, the lower taste score was 6.53 ± 0.05, while the higher was 6.96 ± 0.09. The lowest value was found in the control sample, while the highest was found in the 6% SLPP sample. After 20 days of storage, the lower value was measured, while the higher value was discovered at 0 days. In vacuum packaging, the higher taste value was 6.98 ± 0.09, while the lower taste value was 6.55 ± 0.05. The lowest value was found in the control sample, while the highest value was noted on 6% SLPP sample as shown in Table 7. The current results are matched with Rasarathinam,^[29] who predicted that citrus (Citrus Sphaerocarpa) peel extract could be incorporated into butter formulations without affecting taste attributes.

Odor

The odor of different treated butter samples ranged from 6 ± 0.06 to 6.42 ± 0.09. On 6% SLPP-treated sample, the higher value was found as compared to the control sample. At the 20th day of storage, higher odor value was found. At 0 day storage, lower value was calculated. The odor value of all-butter samples increased with the passage of time. The control sample had the lowest odor score, while the 6% SLPP-treated butter had the highest odor score. With the increase in the concentration of SLPP, the odor score value increased as shown in Table 7.

The lower odor value in aerobic packing was 6 ± 0.06, while the higher was 6.41 ± 0.09. The control sample had the lowest value, while the 6% SLPP sample had the highest value. The higher odor value in vacuum packaging was 6.42 ± 0.09, while the lower was 6.03 ± 0.06. Current findings are in collaboration with Rasarathinam,^[29] who reported that citrus peel extract (Citrus Sphaerocarpa) is incorporated into butter formulations without affecting odor attribute.

Overall acceptability

The overall acceptability of various butter samples ranged from 6.6 ± 0.04 to 6.84 ± 0.09. The highest value was found on 6% SLPP, whereas the lowest value was noted on the control sample. The overall acceptability value was lower at 20th day of storage. The higher overall acceptability was calculated at zero-day storage. According to current results, the overall acceptability of all-butter samples was decreased with the passage of storage intervals. The overall acceptability of the control sample was the highest, while the 6% SLPP-treated butter had the lowest overall acceptability. Current results showed that the overall acceptability value decreased with the increase in the concentration of SLPP, as shown in Table 7.

In aerobic packing, the lower overall acceptability was 6.6 ± 0.04, while the higher overall acceptability was 6.81 ± 0.09. The lowest value was found in the 6% SLPP sample, while the highest was in the control sample. In vacuum packaging, the higher overall acceptability was 6.84 ± 0.09, while the lower overall acceptability was 6.62 ± 0.04. Current findings were matched with Rasarathinam,^[29] who elaborated that citrus peel extract could be incorporated into butter formulations without affecting overall attributes. The findings obtained in the study by Thakaeng et al.,^[25] who suggested that green tea extract, can be used as a butter preservative, antioxidant, and food additive. The findings of previous study justify that the butter samples were fortified with phytosterols. The outcomes showed the high sensory scores comparable with those of the control sample.

Conclusion

It is concluded that SLPP plays an important role in improving quality, stability, antioxidant properties, and sensory parameters of butter. The pH value reduced with the passage of time and SLPP. The L and b values were found to be high in aerobic packaging, whereas the a value was observed to be high in vacuum packaging. The POV and TBARS values are decreased with the increase in the concentration of SLPP, whereas DPPH and TPC amounts are observed to be high with increased SLPP concentration. Microbial load of SLPP-treated butter is found to reduce as compared to the control sample. The negligible variations were measured in sensory parameters including appearance, taste, color, odor, and overall acceptability. It was concluded that the significance of SLPP, storage conditions, and different packaging is suitable and helpful for stability, and improved nutritional value without affecting the sensory parameters of butter.

Acknowledgement

The authors are thankful to the Department of Food Science, Government College University Faisalabad for providing the financial support to conduct this research.

Disclosure statement

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