Study on storage stability of grapes juice preserved with sodium benzoate , potassium sorbate and potassium metabisulphite

This study was carried out to find the effect of potassium metabisulphite, potassium sorbate and sodium benzoate on the preservation and overall quality of grapes juice. Total seven samples were made with this juice which were named as J0, J1, J2, J3, J4, J5, J6. They were kept in plastic bottles and stored at room temperature. All samples were analyzed at fifteen days interval physiochemically (pH, total soluble solids, % acidity, ascorbic acid, reducing and non-reducing sugar) and organoleptically (color, flavor, taste and overall acceptability) for a total period of 90 days. Results obtained from statistical analysis (α< 0.05) showed that storage interval and preservation had significant effect on physiochemical and organoleptic characteristics. Total soluble solids increased maximum in J0 (7.46%) and minimum in J4 (2.79%). Ascorbic acid reduced maximum in J0 (70.40%) and minimum in J2 (29.14%). pH reduced maximum in J0 (17.23%) and minimum in J4 (4.06%). Acidity increased maximum in J0 (41.00%) and minimum in J4 (11.18%). Reducing sugars increased maximum in J0 (69.51%) and minimum in J4 (8.81%). Non-reducing sugars decreased maximum in J4 (83.33 %) and minimum in J2 (36.22 %). Color score decreased maximum for J1 (53.30%) and minimum for J4 (8.00%). Flavor score decreased maximum for J2 (50 %) and minimum for J6 (12.43%). Taste score decreased maximum for J2 (62.66%) and minimum for J4 (8.00%). Overall acceptability score decreased maximum for J2 (54.35%) and minimum for J4 (10.26%). J4 [(grapesjuice + potassium metabisulphite (0.05%) + potassium sorbate(0.05%)] remained very acceptable during storage while J0 [grapes juice + no preservative] was found very bad. Future study is recommonded on microflora assesment, micronutrients assesment, flavonoids and polyphenols extraction which can be added to other food products to prevent cancer in population.


Introduction
Grapes (Vitis vinifera) are belonging to group of berries because of having tiny size and soft structure.They are members of kingdom plantae and genera vitis.sGrapes were actually originated in Turkey.History also have evidences of their presenc in Egypt, Greeks, Europe, North Africa and North America [1].Throughout the world grapes are grown in different countries.According to FAO reporting its world wise yield from 75,866 km 2 was 71% and in the dried farm consumption was recorded 2% of total produced [2].Grapes juice is ever liking product which is directly use for drinking and sometimes it is converted into other products.It is also fermented to produce wines and vinegar.It consists of 89% water having large concentration of glucose and fructose.The acidity content f grapes juice is high because of the presence of tartaric acid, maleic acid and ascorbic acid.They also give a wide range of antioxidants such as flavonoids, anthocyanins, geranial, linalool, nerols and tennins.These antioxidants are responsible for preventing different types of cancers in the body [3].Food graded additives such as benzoate, sorbate etc are added to juices in order to increase their shelf life [4].In juices benzoate is used up to 0.1% for preservation which is recommended amount in juices but some countries have permission for up to 0.15% to 0.25 %.Sorbic acid such as sorbates are widely used as preservative in juices which act as antimicrobial agent to control microorganisms in food and food products [5].It is effective if it is used in the range of 0.03-0.05%.Sorbates are used in the products like jam, jellies while benzoic acid is used in the fruits products such as juices, squashes as they already have acidic pH.It is permitted in the range of 0.01-0.02%which is effective range in these products

Ascorbic acid (mg/ 100g) of grapes juice samples
There was a gradual decrease in ascorbic acid content of samples during storage.The average ascorbic acid value was decreased from 25.8 to 12.5 at α value less than 0.05.Maximum average value was observed in J5 (22.9) and minimum in J2 (16.4).Highest percent decrease in ascorbic acid content was observed in J0 (70.40%) and lowest in J2 (39.27%) as shown in (

Conclusion and recommendations
From this study it was concluded that addition of preservatives strongly affect the products shelf life and consumer acceptability.During this study we found J4 [(grapes juice + potassium metabisulphite (0.05%) + potassium sorbate (0.05%)] remained very acceptable during storage while J0 [grapes juice + no preservative] was found very bad.Future study is recommended on microflora assesment, micronutrients assesment and flavonoids and polyphenols extraction and can be added to other food products to prevent cancer in population.Further study is recommended on refrigeration temperature and mixing of more than two fruits is also recommended to make the product more nutritious.Nutritional assessment and packaging effect study is also recommended for future work.

Table 2 )
. Decrease in ascorbic acid content was also reported by [13] in his work on apple juice samples, by [14] in grape juice samples, by [15] in apple pulp samples, by [16] in apple juice samples, by [17] in kinnow juice samples, and by [18] in mango leather samples.

Table 3
). Decrease in pH during storage was also reported by [19] in guava pulp samples, by [20] in strawberry juice samples, by [21] in pineapple leather samples and by [22] in cashew apple juice samples.

Table 7 . Effect on non-reducing sugars of grapes juice samples Treatments Storage intervals (Days) Average %Decrease
00%) as shown in (Table 8).The same decrease in color score was shown by [32] in post-harvest dried samples and by [33] in lime and orange juice samples.