Optimization of Palmyrah (Borrasus flabellifer) Fruit Pulp in Different Varieties of Fruit Yoghurts

Abstract

The research focused on processing palmyrah fruit pulp into a value added product to broaden the utilization of palmyrah fruit pulp. Set, swiss style, jelly and pulp preserve yoghurts incorporated with palmyrah fruit pulp were developed. Control yoghurt and plain yoghurt for other preparations were prepared with 13 % sugar, 1% gelatin, 12 % skim milk powder and lactic acid bacteria culture following household method. The fresh pulp was kept at – 25 oC for 48 hours and heated up to 85 oC for 30 minutes with 5 % cane sugar, 0.6 % tartaric acid, 1 % ascorbic acid and 0.13 % sodium chloride. The treated pulp was added at 5 %, 7.5 %, 10 %, 12.5 % and 15 % into both set and swiss style yoghurts. Fruit jelly was prepared with sugar, gelatin, sodium citrate, citric acid and 20 % pulp. It was then incorporated into yoghurt at 5 % and 6 %. Palmyrah fruit pulp preserve was prepared by heating sugar, pectin and pulp (45. 8 %) until its brix reached 68.5 o and it was topped on set yoghurt at 5 %, 7.5 % and 10 %. Sensory evaluation for colour, odour, appearance, mouth feel and texture was conducted with 21 untrained panelists using 5 point hedonic scale and the optimized pulp concentrations for set, swiss style, jelly and preserve yoghurt were 5 %, 7.5 %, 6 % and 10 % respectively (p < 0.05). The overall sensory qualities of all palmyrah fruit yoghurts were rated as good to very good. There were no significant changes in sensory attributes, brix and pH in storage at 4 oC. Shelf life was 18 days for all products at 4 oC without any preservatives except set yoghurt as it showed separation of water from the third day of the preparation. Nutritional and microbiological qualities of the products were investigated and compared with control yoghurt. Protein was higher in swiss style (6.12 %) and jelly (7.77 %) yoghurts. Carbohydrate was higher in swiss style yoghurt (36.87 %) and preserve yoghurt contained highest fat content (2.57 %).