S. G. Kulkarni

Effect of pectinase treatment and concentration of litchi juice on quality characteristics of litchi juice

Litchi (Litchi chinensis L) juice concentrate was prepared from pulp extracted from ripe fruits. Clarification of litchi pulp was optimized using pectinase at different concentrations. Litchi pulp treated with pectinase enzyme facilitated the removal of insoluble solids and extraction of juice. Vacuum concentration of clarified juice was carried out in a pilot scale turbafilm vacuum evaporator to obtain litchi juice concentrate with total soluble solids of 60°Brix. The litchi juice concentrate contained 49.9% total sugars, 47% reducing sugars, 32.7 mg/100 g ascorbic acid and its titratable acidity was 0.73%. The litchi juice concentrate was stored at −20°C for 6 months and analyzed at regular intervals for changes in quality. No significant changes in the composition of juice concentrate was observed during storage except tannin content and non-enzymatic browning which increased during storage. Single strength litchi juice reconstituted from juice concentrate was highly acceptable sensorily during 6 months storage.

Effect of processing of dates into date juice concentrate and appraisal of its quality characteristics

Date palm (Phoenix dactylifera) is widely cultivated in Kutch district of Gujarat and the fruits are harvested at immature stage before the onset of monsoon to prevent spoilage. The immature date fruits with less commercial value were used for processing into date juice concentrate. Immature dates were crushed and treated with 0.1% pectinase enzyme for 120 min to obtain maximum juice. Date juice was found to be rich in reducing sugars (16.1%) and total sugars (18.3%). Juice was pasteurized at 85°C to inactivate the enzyme, cooled and centrifuged at 3000 rpm to get clear juice. The juice was concentrated in a thin film evaporator to a total soluble solids (TSS) of 76°Brix in 2 passes. Chemical composition of date juice during different stages of concentration was determined. Date juice concentrate was packed in low density polyethylene bags of size (22 cm × 14 cm) and frozen in blast freezer at −40°C and stored at −20°C. Storage of date juice concentrate at −20°C for 6 months indicated no significant changes in TSS, acidity, ascorbic acid, total sugars and pH. Hunter colour lightness L, and redness a values of date juice concentrate decreased whereas b values increased during storage. Date juice concentrate was stable during 6 months storage could be reconstituted for preparing ready-to-serve beverages with acceptable sensory quality.