Quality evaluation of strawberry squash stored at ambient temperature

The research work was conducted to find out the effect of sodium benzoate and potassium sorbate on the overall quality of strawberry squash, stored at ambient temperature for 90 days. The research samples were numbered as T1 (strawberry squash without preservative), T2 (0.1% sodium benzoate), T3 (0.1% potassium sorbate), T4 (0.05% sodium benzoate + 0.05% potassium sorbate), T5 (0.075% sodium benzoate + 0.025% potassium sorbate). The samples were studied for pH, TSS, % acidity, ascorbic acid, reducing sugar, non-reducing sugar and organoleptic evaluation (color, flavor, taste and overall acceptability). A decrease was observed in pH (2.86 to 1.92), TSS (49.50 to 42.76), ascorbic acid content (41.75 to 24.74), non-reducing sugar (26.12 to 24.47) and an increase in % acidity (1.31 to 1.97) and reducing sugar (10.40 to 11.85). During sensory evaluation, the sample T4 (0.05% sodium benzoate + 0.05 % potassium sorbate) was found most acceptable. Statistical analysis showed that the treatments and storage intervals had a significant (P<0.05) effect on the physicochemical and organoleptic analysis of strawberry squash.

as "Fraise" or "Fragrant berry". About 250 years ago strawberry came from two different countries, North and South America and then brought to Europe. It is grown in most part of the world but is extensively grown in USA, Japan, Mexico, Italy and Labenon [2]. Due to its delicious flavor and attractive color the consumer's demand for the fruit is increasing not only in Pakistan but also in other parts of the world. Strawberry fruit is mainly consumed as fresh, but is also used in processed form as cooked and sweetened preserves i.e. jams, jellies and frozen whole berries. The sweetened juice extract or flavoring is used in making variety of other processed products [3]. Potassium sorbate is also worn in several special concern produce to retard the growth of micro-organisms for ledge. Sodium benzoate is a bacteriostatic and fungistatic preservative underneath acidic environment and is mostly worn in acidic foods like salad dressings (vinegar), carbonated munchies (carbonic acid) and condiments. It can as well be originate in alcohol based mouth wash and in cough syrups. Labeling of this preservative reads as "sodium benzoate" on an ingredient statement or E-211 [4]. Strawberry also contains phyto-nutrients and antioxidants which fight free radicals. The non-reducing sugars on the storage decreases, undergoes inversion changed into reducing sugars. Strawberries also provide an excellent source of vitamin K, riboflavin, vitamin B5, vitamin B6, magnesium, potassium, copper, manganese as well as folic acid and omega 3 fatty acids [5]. pH of strawberry ranges from 3.27-3.86 which stabilizes color. Titratable acidity ranges from 0.51-1.35 g/100g. Malic and Citric acids are primary organic acids which contribute to flavor. Total soluble solids ranges between 8.0-11.5% and are ideal for juice concentrate required in the market. A soluble solid per acid ratio 8.52-13.7g is a balance of sweetened flavor. Strawberry per 100g contains 90.9g water, 0.7g protein, 7.7g carbohydrates, 0.3g fats, 16.0mg calcium, 0.4mg iron, 13.0mg magnesium, 1.0mg sodium, 58.8mg vitamin C and 12.0 IU vitamin A [6]. Keeping in view the perishability of strawberry fruit, the present study was designed to prepare a value added product from strawberry i.e. squash which will be available throughout the year in a market. The farmers will be benefitted while getting proper return for their produce.

Materials and methods
Sound and healthy strawberries of proper size and optimum maturity were purchased from the local market of Peshawar and brought to the laboratories of Food Technology Center, Pakistan Council of Scientific and Industrial Research (PCSIR) Peshawar, where a research work was conducted. After sorting and washing, the stalks of strawberry fruits were removed by using stainless steel knives. The pulp was extracted with the help of a pulper and strained through muslin cloth and used for squash preparation in the ratio of 1:1:1. Citric acid was also added to adjust the acidity to 1% along with 0.05% Carboxy Methyl Cellulose (CMC) to avoid separation. The treatments were made as T1 = Strawberry squash without preservative (Control), T2 = Sodium benzoate 0.1%, T 3= Potassium sorbate 0.1%, T4= Sodium benzoate 0. 05% + Potassium sorbate 0. 05% and T5= Sodium benzoate 0.075% + Potassium sorbate 0.025%.

Packaging and storage of squash
The ready squash samples were packed in sterilized 250ml capacity clear glass bottles and were kept at ambient temperature for physico-chemical and sensory analysis at intervals of 15 days for a total period of 3 months. Chemical analysis Ascorbic acid was determined by the direct colorimetric method using 2,6dichlorophenol-indophenols as decolorizing agent by ascorbic acid in sample extract and in standard ascorbic acid solution [7]. Acidity was determined by standard method of [7]. Inolab digital pH meter was used for pH determination. Reducing and non-reducing sugars were determined by Lane Eynon method [7]. The total soluble solids TSS were determined by using Abbe refractometer at room temperature [7]. Sensory evaluation A panel of judges selected from students of food science department evaluated the product fortnightly for color, flavor, taste and overall acceptability by the method of [8] using a scale from 1 to 9, where 1 represents extremely disliked and 9 represents 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 [9]. For all the analysis, the alpha error was set at 0.05%.

Results and discussion Chemical analysis
The statistical analysis indicated that storage intervals and temperature had a significant effect on pH of all the samples .The mean pH values of all the samples decreased from 2.86 to 1.92 during storage. Maximum percent decrease was recorded in T1 (47.90%), while minimum in T4 (24.83%) ( Table 1). These results are in close conformity with the findings of [10] who observed a decrease in pH of citrus fruit beverage. The data showed that different treatments and storage intervals had a significant effect on ascorbic acid content of different samples. There was a gradual decrease in ascorbic acid of strawberry squash from 41.75 mg to 24.74 mg. Minimum percent decrease was recorded in sample T4 (32.53%) and maximum in T1(58.63%) ( Table 2). In a similar study [11] reported a decrease in ascorbic acid in juices during storage. These results are also in agreement with the findings of [12] who recorded a change in Chalder variety of strawberries stored at 4 0 C. Acidity of samples (T1 to T5) were gradually increased during three months of storage. Results showed that reducing sugars increased in all the samples from 10.40 to 11.85% during three months of storage. The treatments and storage intervals had a significant effect on reducing sugar of strawberry squash. Maximum percent increase was observed in T1 (18.56%) while minimum percent increase was noted in T2 (10.23%) ( Table 5). These results are in agreement with [16] who showed an increase in glucose and fructose contents in strawberry fruits. Similar findings were also reported by [17] that non reducing sugars of drinks is converted into reducing sugars during storage. The non-reducing sugars decreased in all the samples from 26.12 to 24.47%. The maximum mean value was noted in T4 (25.63), while minimum mean value was observed in T1 (24.74). Minimum percent decrease was noted in T4 (5.09%) and maximum in T1 (9.80%) ( Table 6). These results are confirmed by [16] who suggested that the sucrose content of the fruit convert to glucose and fructose during storage, results in the change of sucrose contents of the juices. Similar trends of decreasing non-reducing sugars were also observed by [18] during studies on mango squash.

Sensory analysis
The analysis of the data showed that storage period and treatments had a significant effect on overall acceptability (obtained from color, flavor and taste) of strawberry squash. The mean score of judges decreased from 8.15 to 3.41.