International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 36 Storage Studies of Strawberry Juice with TSS of 7.5 and 20.5 o Brix Preserved with Sodium Benzoate and Potassium Sorbate Stored at Ambient Temperature *Shakoor Wisal, *Manzoor Ahmad Mashwani and **Saqib Noor *Department of Agriculture, Bacha Khan University Charsadda, Pakistan **Department of Food Science and Technology, The University of Agriculture Peshawar, Pakistan Author address: swisal@aup.edu.pk Abstract-- This research was carried out to investigate the effect of different sugar concentrations and chemical preservatives and storage temperature i. e. ambient temperature (20-25 o C) on the physicochemical and sensory attributes of strawberry juice stored for three months. The samples were numbered as, T A0, T A1, T A2, T A3, T A4, T A5, T A6 and T A7. Maximum increase in total soluble solids (TSS) content occurred in T A1 and T A2 (20.00%) while minimum change occurred in T A7 (7.31%). Maximum decrease in ph content occurred in T A0 (17.9%) while minimum decrease was observed in T A7 (9.72%). Maximum increase in titratable acidity occurred in T A0 (167.40%) followed by T A4 (141.90%) while minimum increase occurred in T A7 (122.85%). Maximum ascorbic acid decreased in T A0 (83.06%) followed by T A4 (77.79%) while minimum decreased was observed in T A7 (66.43%). Maximum increase in reducing sugar content was occurred in T A6 (25.86%) while minimum increase occurred in T A3 (17.93%). Maximum decrease was observed in non reducing sugar content occurred in T A4 (87.70%) while minimum decrease occurred in T A3 (18.30%). Maximum decrease in color was recorded for T A0 and T A4 (83.75%). Flavor deterioration occurred in control samples i. e. T A0 and T A4. Comparatively better consistency was recorded by sweetened juice. Among all the treatments T A0 and T A4 were rejected soon after storage due to spoilage while T A7 was found most effective but was also rejected organolytically after sometime. It is the result of our research work that temperature plays most important role in extending shelf life. Index Term-- Strawberry juice, benzoate, sorbate, sucrose, ambient temperature. INTRODUCTION One of the most important among the berries is strawberry which belongs to the family "Rosaceae". It is thought that berries are important against several types of cancers [11]. It is grown in many countries of the world, but is grown widely in the United States, Japan, Mexico, Italy and Lebanon [17]. Strawberries are also grown wildly with a pleasant flavor but smaller in size [7]. Gradually grown in Pakistan because of its scope in the future is bright for farmers and fruits can be traced maximum economic benefit to farmers. There are certain factors which effect the production of strawberry for example scientifically grown strawberries give higher production than conventional cultivation [20]. Strawberries can be successfully grown in cold areas in the tropics and subtropics. Mature fruit in a short period of time which is 30 to 40 days, non-perishable and must be consumed in early after winning. Must be handled carefully and fruit, while the transfer to the market long as there are prospects for the deterioration of fruit during transportation [2]. Strawberries are the first fresh fruit in the market during the spring. Because of the delicious flavor and attractive color and structure of the format, and consumer demand for fruit growing, not only in Pakistan but also in other parts of the world. And consumed mainly of fruits and fresh, and are also used in the form of treatment such as canned cooked and sweetened, and that is, jam, jelly and frozen whole berries. Several products are prepared from it such as purees, jam, juice and wine etc. [17]. The fruit is firm, red meat and sweet. More than 50% of sucrose in strawberry is glucose. Fruit contains citric acid, and often some malic acid. The red color of fruit is due to the presence of anthocyanin pigment. Volatile esters responsible for many of the fruit flavor are found in it. Of nutritionally and strawberries contain carbohydrate lowcalorie and a potential source of vitamin C, fiber and provides more vitamin C than oranges. The main components of fruit, vitamin C in strawberries is (64.0 mg), water (91.75 g) and protein (0.61 g), fat (0.37 g) and carbohydrate (7.02 g), fiber (2.3 grams), calcium (14.0 mg) and potassium (166.0 mg/160 g), respectively, and vitamin (a) (27). International units, ranging in ph from 3.27-3.86, which helps in achieving stability in the ph range of color from 0.58 to 1.35%, and citric acid and malic and organic acids that contribute to excellent flavor. TSS is in the range 8.0 up to 11.5%, and is ideal for juice called for in the market. Soluble solids / acid ratio from 8.52 to 13.79 are a good balance of sweet tart flavor [21]. In the past decade there has been a significant increase in the demand for strawberries because the juice to have excellent flavor with an attractive color. However, being the result of a soft tight little fluctuation in temperature results in damage and waste of fruit. Due to the lack of other storage facilities to keep the product in the form of raw materials, this study has begun to take advantage of the fruit is very perishable in the form of juice, and study the effect of chemical preservatives on the quality of conservation of strawberry juice stored at ambient temperature. Potassium sorbate is important in the preservation of juices during storage [4]. Sodium benzoate can maintain the good quality of fruit juices during preservation [4]. It is hoped that these results will help beverage industries to take advantage of this fruit juice to prepare with the shelf stability and the growing demand for
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 37 consumer goods. This offer high-yield income for farmers, and will improve the economy of Pakistan. MATERIALS AND METHODS Fresh mature and sound strawberries were purchased from the local fruit market of Peshawar and were brought to Food Processing and Analytical Laboratory of the Department of Food Science and Technology, The University of Agriculture Peshawar, Pakistan where research work was carried out. The strawberries were washed followed by sorting, the juice was extracted using juice extracting machine. Before filling in glass bottles the juice was pasteurized. The samples were numbered as, T A0 =Strawberry juice (7.5 brix) - no preservatives (control), T A1 =Strawberry juice (7.5 brix) with 0.1% sodium benzoate, T A2 =Strawberry juice (7.5 brix) with 0.1% potassium sorbate, T A3 =Strawberry juice (7.5 brix) with 0.05% sodium benzoate+0.05% potassium sorbate, T A4 =Strawberry juice (20.5 brix) - no preservatives (control), T A5 =Strawberry juice (20.5 brix) preserved with 0.1% sodium benzoate, T A6 =Strawberry juice (20.5 brix) with 0.1% potassium sorbate, T A7 =Strawberry juice (20.5 brix) with 0.05% sodium benzoate + 0.05% potassium sorbate,. The juice was filled in glass bottle, sealed and stored at ambient temperature (20-25 C) for a period of three months. Chemical analysis The total soluble solids (TSS) were determined by using Abbe refractometer at ambient temperature [3]. Inolab digital ph meter was used for ph determination. Acidity was determined by dissolving a known weight of sample in distilled water and titration against 0.01 N NaOH using phenolphthalein as indicator [18]. Ascorbic acid was determined by the direct colorimetric method using 2, 6- dichlorophenol- indophenols as decolorizing agent by ascorbic acid in sample extract and in slandered ascorbic acid solution [3]. Reducing and non-reducing sucrose was determined by lane Eynon method [3]. Sensory evaluation A panel of ten judges selected from staff and students of food science department evaluated the product fortnightly for color, flavor, consistency and overall acceptability by the method of [9] using a scale from 1 to 9, where 1 represented extremely disliked and 9 represent extremely liked. Statistical analysis The data obtained was subjected to statistical analysis using RCBD (Randomized Complete Block Design) and the means were compared by using LSD (Least Significant Difference) test [19]. For all the analyses, the alpha error was set at 0.05%. RESULTS AND DISCUSSION Chemical analysis Our results indicated that storage period and temperature had significant effect on total soluble solids (TSS) during storage. Maximum increase occurred in T A1 and T A2 (20.00 %) followed by T A3 (13.33 %) while minimum increase was recorded in T A7 (7.31 %) followed by T A5 and T A6 (9.75 %). Decrease occurred T A0 and T A4 during storage. These results are in agreement with the results obtained by [23] during preservation of grape juice stored at room temperature for one month preserved with sodium benzoate and potassium sorbate. Similar results were obtained by [8] during storage of apple and apricot blended juice storage at refrigeration temperature for three months. Increase in total soluble solids may be due to break down of polysaccharides into monosaccharide and oligosaccharides while decrease may be due to fermentation of sugars into ethyl alcohol, carbon dioxide and water. During storage maximum decrease in ph content was observed in T A0 (17.94 %) followed by T A4 (16.11 %) while minimum decrease was observed in T A3 (8.83 %) followed T A7 (9.72 %). Similar results were recorded by [10] during study of the effect of pasteurization and chemical preservatives on the quality and shelf stability of apple juice stored at ambient temperature for three months. During storage of apple and apricot blended juices storage, preserved with sodium benzoate at refrigeration temperature for three months by [8], decrease in ph was recorded. Decrease in ph may be due to conversion of pectin into pectenic acid, which increases acidity and decreases ph of the juice. Storage and treatments has a significant effect on the titratable acidity of strawberry juice. Maximum increase was observed in T A0 (167.40 %) followed by T A4 (141.90 %) while minimum increase was observed in T A7 (121.85 %) followed by T A3 (125.18 %). Similarly increase in titratable acidity was observed by [23] during preservation of grape juice with sodium benzoate and potassium sorbate, stored at room temperature for one month storage period. The results of [5] are in agreement with our results, who observed an increase in acidity of pomegranate syrup, preserved under different light conditions and different packaging materials at room temperature for storage period of four months. This increase might be due to acidic compounds formed by degradation or oxidation of reducing sugar and high temperature. Increase in titratable acidity may be due to the breakdown of pectin into pectenic acid or due to the formation of acid by the breakdown of polysaccharides or oxidation of reducing sugars. Ascorbic acid is the most difficult vitamin to be preserved during storage. As it is the least stable vitamin, it decreases in the product during storage. Maximum decrease was observed in T A0 (83.06 %) followed by T A4 (77.79 %) while minimum percent decrease was observed in T A7 (66.43 %) followed by T A5 (70.27 %). The results are in agreement with the findings of [23] during preservation of grape juice with sodium benzoate and potassium sorbate, stored at room temperature for one month storage period, who observed decrease in ascorbic acid content of grape juice. The results of [5] are in agreement with our results, who observed decrease in ascorbic acid content of pomegranate syrup, preserved under different light conditions and different packaging materials at room temperature for storage period of four months. The losses may be due to oxygen present in the product and headspace of the package. Sugars are the most important constituent of fruit product and are essential factor for the flavor of the food product and also act as a natural food preservative. Results showed that reducing sugars increased in all samples in which maximum increase was observed in T A6 (25.86 %) followed by T A5 (25.61 %) while minimum increase was observed in
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 38 T A3 (17.93 %) followed by T A1 (18.62 %) while control samples showed decrease during storage period. Maximum decrease was observed by [10] observed an increase in reducing sugar of apple juice preserved with chemical preservatives stored at ambient temperature for three months. Increase in reducing sugar of apple and apricot blended juice, preserved with sodium benzoate at refrigeration temperature for three months, and was observed by [8]. This increase in reducing sugar might be due to conversion of sucrose to reducing sugars (glucose and fructose) primarily due to acids and higher temperature. Maximum decrease in non reducing sugar was observed in T A4 (87.80 %) followed by T A0 (78.87 %) while minimum decrease was observed in T A3 (18.30 %) followed by T A1 (19.71 %). [10] observed decrease in non reducing sugar of apple juice preserved with chemical preservatives stored at ambient temperature for three months. Increase in reducing sugar of apple and apricot blended juice, preserved with sodium benzoate at refrigeration temperature for three months and was observed by [8]. This decrease in non reducing sugar might be due to conversion of sucrose to glucose and fructose, primarily due to increase in acidity and high storage temperature and storage period length. Sensory evaluation The analysis of our data showed that storage period and treatments had a significant effect on overall acceptability (obtained from color, flavor, consistency and overall acceptability) of the strawberry juice. It was recorded that control samples were spoiled soon after storage and resulted in producing off flavor, maximum loss in color, consistency and overall acceptability while the treated samples retained comparatively better quality for longer period. The results are in agreement with the findings of [23] during preservation of grape juice with sodium benzoate and potassium sorbate, stored at room temperature for one month storage period, who observed decrease in color of grape juice. The results of [5] are in agreement with our results, who observed decrease in flavor of pomegranate syrup, preserved under different light conditions and different packaging materials at room temperature for storage period of four months. These results are in agreement with findings of [12], who observed decrease in consistency of ready to serve beverages prepared from palmyrah fruit pulp and stored at room temperature for six months. CONCLUSION From the study it was concluded that sugar concentration and combination of preservatives play a positive role in extending the shelf life of strawberry juice. It was concluded that T A7 =Strawberry juice (20.5 brix) with 0.05% sodium benzoate + 0.05% potassium sorbate maintained better quality followed by T A5 =Strawberry juice (20.5 brix) with 0.1% sodium benzoate during storage at ambient temperature (20-25 o C) for three months. These samples were acceptable to the consumers on the basis of physico chemical attributes but were rejected on the basis of sensory attributes during experiment. Table I Effect of storage at ambient temperature (20-25 0 C) on TSS of strawberry juice samples Initial 20 40 60 80 % Inc/ dec Mean TSS (Total Soluble Solids content of juice T A0 7.5 3.5 3.5 3.0 2.5 66.66 * 4.000 b T A1 7.5 7.5 8.0 8.5 9.0 20.00 8.100 a T A2 7.5 7.5 8.0 8.5 9.0 20.00 8.100 a T A3 7.5 7.5 7.7 8.0 8.5 13.33 7.840 a T A4 20.5 16.0 8.0 7.0 6.5 68.29 * 11.60 b T A5 20.5 21.5 21.5 22.0 22.5 9.75 21.60 a T A6 20.5 21.0 21.5 22.0 22.5 9.75 21.50 a T A7 20.5 21.0 21.0 21.5 22.0 7.31 21.20 a
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 39 Table II Effect of storage at ambient temperature (20-25 0 C) on ph of strawberry juice samples ph value T A0 3.51 3.25 3.10 3.01 2.88 17.94 3.15 b T A1 3.51 3.35 3.32 3.23 3.14 10.54 3.31 a T A2 3.51 3.32 3.25 3.20 3.17 9.68 3.29 a T A3 3.51 3.35 3.28 3.25 3.20 8.83 3.32 a T A4 3.60 3.30 3.21 3.13 3.02 16.11 3.25 b T A5 3.60 3.34 3.30 3.27 3.24 10.00 3.35 a T A6 3.60 3.34 3.30 3.26 3.23 10.27 3.34 a T A7 3.60 3.35 3.31 3.28 3.25 9.72 3.35 a Table III Effect of storage at ambient temperature (20-25 0 C) on acidity of strawberry juice samples Initial 20 40 60 80 % Increase Mean Acidity (%) content of juice T A0 1.35 2.12 2.82 3.42 3.61 167.40 2.66 b T A1 1.35 1.92 2.43 2.92 3.22 138.51 2.36 c T A2 1.35 1.92 2.45 2.95 3.24 140.00 2.38 c T A3 1.35 1.82 2.08 2.78 3.04 125.18 2.21 d T A4 1.05 1.76 2.12 2.40 2.54 141.90 1.97 c T A5 1.05 1.45 1.72 2.12 2.46 134.28 1.76 d T A6 1.05 1.46 1.70 2.00 2.42 130.47 1.72 d T A7 1.05 1.42 1.65 1.98 2.34 122.85 1.68 d
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 40 Table IV Effect of storage at ambient temperature (20-25 0 C) on ascorbic acid of strawberry juice samples Ascorbic acid content mg/100 kg T A0 31.30 20.11 10.53 5.52 5.30 83.06 14.55d T A1 31.30 23.53 12.45 8.50 7.00 77.63 16.55cd T A2 31.30 24.45 13.80 8.50 7.00 77.63 17.01c T A3 31.30 26.94 15.70 10.50 8.50 72.84 18.59c T A4 28.60 17.46 9.00 7.00 6.30 77.79 13.67e T A5 28.60 22.70 16.10 10.00 8.50 70.27 17.18cd T A6 28.60 20.95 13.80 10.00 8.30 70.97 16.33d T A7 28.60 24.45 18.40 12.00 9.60 66.43 18.61c Table V Effect of storage at ambient temperature (20-25 0 C) on reducing sugar of strawberry juice samples Initial 20 40 60 80 % Inc/dec Mean Reducing sugar content T A0 5.80 2.82 2.70 2.32 1.93 66.72* 3.11b T A1 5.80 6.26 6.54 6.76 6.88 18.62 6.44a T A2 5.80 6.28 6.56 6.80 6.94 19.65 6.47a T A3 5.80 6.24 6.52 6.74 6.84 17.93 642a T A4 15.85 12.37 6.17 5.41 5.02 68.32* 8.96 b T A5 15.85 17.48 18.46 19.26 19.91 25.61 18.19 a T A6 15.85 17.50 18.50 19.30 19.95 25.86 18.22 a T A7 15.85 17.40 18.32 19.10 19.70 24.29 18.07 a
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 41 Table VI Effect of storage at ambient temperature (20-25 0 C) on non-reducing sugar of strawberry juice samples Non-reducing sugar T A0 1.42 0.58 0.48 0.38 0.30 78.87 0.63 b T A1 1.42 1.32 1.24 1.18 1.14 19.71 1.26 a T A2 1.42 1.30 1.22 1.16 1.12 21.12 1.24 a T A3 1.42 1.32 1.26 1.20 1.16 18.30 1.27 a T A4 3.74 2.67 0.96 0.64 0.46 87.70 1.69 b T A5 3.74 3.26 2.92 2.72 2.59 30.74 3.04 a T A6 3.74 3.24 2.88 2.68 2.56 31.55 3.02 a T A7 3.74 3.28 2.96 2.74 2.62 29.94 3.06 a Table VII Effect of storage at ambient temperature (20-25 0 C) on color of strawberry juice samples Color score rate T A0 8.00 3.00 2.00 1.67 1.30 83.75 3.19 b T A1 8.00 6.00 3.00 2.67 2.00 75.00 4.33 a T A2 8.00 6.00 3.00 2.67 2.00 75.00 4.33 a T A3 8.00 6.00 3.00 2.67 2.00 75.00 4.33 a T A4 8.00 4.00 1.67 1.50 1.30 83.75 3.29 b T A5 8.00 6.30 3.00 3.00 2.00 75.00 4.46 a T A6 8.00 6.30 3.00 3.00 2.00 75.00 4.46 a T A7 8.00 6.60 3.00 3.00 2.00 75.00 4.52 a
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 42 Table VIII Effect of storage at ambient temperature (20-25 0 C) on flavor of strawberry juice samples Flavor score rate T A0 8.00 1.67 1.50 1.30 1.30 83.75 2.75 b T A1 8.00 5.30 2.30 2.00 1.67 79.12 3.85 a T A2 8.00 5.30 2.30 2.00 1.67 79.12 3.85 a T A3 8.00 5.30 2.30 2.00 1.67 79.12 3.85 a T A4 8.00 1.67 1.50 1.30 1.30 83.75 2.75 b T A5 8.00 6.30 3.00 2.00 2.00 75.00 4.26 a T A6 8.00 6.30 3.00 2.00 2.00 75.00 4.26 a T A7 8.00 6.60 3.00 2.00 2.00 75.00 4.26 a Table IX Effect of storage at ambient temperature (20-25 0 C) on consistency of strawberry juice samples Consistency score rate T A0 7.00 5.50 2.00 2.00 1.30 81.42 3.56 b T A1 7.00 6.00 2.67 2.00 1.30 81.42 3.79 ab T A2 7.00 6.00 3.00 2.00 1.30 81.42 3.86 a T A3 7.00 5.50 3.00 2.00 1.30 81.42 3.76 ab T A4 7.00 5.50 2.00 2.00 1.30 81.42 3.56 b T A5 7.00 6.30 3.30 3.00 2.00 71.42 4.32 a T A6 7.00 6.30 3.00 3.00 2.00 71.42 4.26 a T A7 7.00 6.00 3.00 3.00 2.00 71.42 4.20 a
International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:14 No:01 43 Table X Effect of storage at ambient temperature (20-25 0 C) on overall acceptability of strawberry juice samples Overall acceptability score rate T A0 8.00 2.60 2.00 1.67 1.30 83.75 3.11 b T A1 8.00 6.00 2.30 2.30 1.30 81.25 3.98 a T A2 8.00 6.00 2.30 2.67 1.30 81.25 4.05 a T A3 8.00 6.00 2.30 2.67 1.30 81.25 4.05 a T A4 8.00 2.50 2.00 1.30 1.30 83.75 3.02 b T A5 8.00 6.00 3.30 2.67 2.00 81.25 4.29 a T A6 8.00 6.00 3.00 2.67 2.00 81.25 4.23 a T A7 8.00 6.00 3.00 3.00 2.00 81.25 4.30 a REFERENCES [1] Ali M (1965). Canning of fruits and vegetables and their juices. Effect of canning quality of juices from different varieties of oranges. M.Sc. Agriculture. Thesis, Agricultural. University., Faisalabad. [2] Amin NU (1996). Evaluation of different strawberry cultivars for offseason production under plastic tunnel. P.I. M.Sc. (Hons) thesis, Department of Horticulture NWFP Agricultural University. 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