Litchi pulp was treated with various concentration levels of hydrolytic enzymes viz. pectinase (0-0.133%w/w), cellulase (0-0.266%w/w) and hemicellulase (0-0.20%w/w) for different durations (30-150 min) at 45°C. The effect of enzyme treatment conditions was studied on yield, clarity, apparent viscosity and total soluble solids (TSS) of juice obtained from the pulp. The optimum process conditions were determined by employing a second order central composite rotatable design in combination with response surface methodology. Yield, clarity and TSS of juice were found to increase and apparent viscosity was found to decrease significantly by enzymatic treatment. The optimum conditions for enzymatic treatment of pulp obtained after a 2 sided desirability function with the responses juice yield, clarity and TSS to be maximized and viscosity to be minimized were 0.076% (w/w) pectinase, 0.138% (w/w) cellulase, 0.107% (w/w) hemicellulase and incubation time of 106.5 min. The predicted values for juice yield, clarity, viscosity and TSS under optimized conditions were 77.19%, 93.53%, 1.359mPa s and 19.68°brix which showed a good agreement with the experimental values under same set of conditions.
Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0-2% (w/v) calcium lactate (CL), 0-0.02% (w/v) 4-hexyl resorcinol (4-HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over-wrapped with polypropylene film, vacuum-packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2°C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four-factor, three-level experimental design (D 6 Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4-HR, in-package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 6 0.01), whereas drip losses and microbial count increased significantly (P 6 0.01) with time. Drip loss was significantly (P 6 0.1) reduced by addition of CL. 4-HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 6 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.
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