Production And Evaluation Of Gudeim (grewia Tenax) Juice

Abstract

The objectives of this study are, to determine the most appropriate mechanical extraction method, the most effective stabilizer (in recipe formulation), and the most suitable processing and storage protocol for Gudeim juice production. For that two experiments were used. A 3×3 factorial experiment (3 mechanical extraction methods and 3 stabilizers) and a 2×5 factorial experiment (2 processing protocols and 5 storage periods). Physicochemical, microbiological, and sensory analysis were conducted to evaluate the experiments results. Nutritional value was also calculated. Three mechanical methods were used to extract the juice from Gudeim fruits soaked in drinking water at the ratio of 1:4 (fruit to water): crushing and pressing method (MM-1); counter current flow and pressing method (MM-2); stirring and blending method (MM-3). Three stabilizers were used with the extracted juice in three recipe formulations: mixture of cellulose and xanthan gums in recipe one (R-1); pectin in recipe two (R-2), and xanthan gum in recipe three (R-3). The formulated juice was processed in two protocols: Cold: pasteurization followed by cold filling in PET bottles and cold storage; Hot: pasteurization followed by hot filling in Glass bottles and ambient storage. Five storage periods (0, 15, 30, 45, and 60 days) were tested. The results of experiment one: showed that the mechanical extraction methods MM-1, MM-2 and MM-3 gave a juice yield of 59, 73 and 76% respectively. Consequently (MM-3) was selected as the most appropriate mechanical extraction method for Gudeim juice. the stabilizers used in recipes (R-1, R-2 and R-3) decreased serum separation from 30 ml/100 ml juice without stabilizer to 0.06 ml, 10.0 ml and 0.02 ml respectively. Accordingly xanthan gum in (R-3) was recognized as the most appropriate stabilizer for Gudeim juice recipe formulation. The results of experiment two: showed that the juices from both cold and hot processing protocols were free from total coliforms bacteria, E. coli bacteria, lactic acid bacteria, yeasts and moulds throughout storage periods tested. Juice produced by cold processing protocol was found to have less xiii serum separation (0.01 ml/100 ml), high total soluble solids concentration and higher titratable acidity than juice produced by hot processing protocol. The effect of the storage periods on the different Gudeim juice parameters measured depends upon the processing protocol. The highest amount of Gudeim juice serum separation (0.15 ml/100 ml) was noted on hot processing protocol on the 60th day of storage. Gudeim juice was found to have sizable amounts of nutrients particularly: energy 30.56 kcal/100ml; carbohydrate 6.73g/100ml; iron 7.02 ppm; potassium 1610 ppm and vitamin C 24 mg/100ml juice. The polyphenols analysis showed that Gudeim fruit flesh had 16.2 mg/100g of flavonols and 5.59 g/100g of proanthocyanidins, while Gudeim juice had 1.78 mg/100g of flavonols and 614 mg/100 of proanthocyanidins. The sensory evaluation results showed that color, aroma, taste and overall acceptability of Gudeim juice from cold processing protocol had higher scores (7.14-8.18) at all storage periods tested, than the one from hot processing protocol (6.10- 7.32). Thus Gudeim juice from cold was more liked by panelists than the one from hot processing protocol. A combination of an appropriate mechanical extraction method, the best stabilizer (xanthan) in the formulation and cold processing protocol were suggested for Gudeim juice production.