No abstract

The effect of enzyme concentration (0.16-0.84 mg/100 g guava pulp), incubation temperature (36.6-53.4°C), and incubation time (0.95-11 h) on juice yield was studied. A central composite rotatable design was used to establish the optimum conditions for enzymatic hydrolysis of guava to obtain maximum juice yield. Significant regression model describing the changes of juice yield with respect to hydrolysis parameters were established with the coefficient of determination, R 2 =0.85. Enzyme concentration was the most significant variable affecting the juice yield. The recommended enzymatic treatment condition from the study was at the enzyme concentration 0.70 mg/ 100 g guava pulp, incubation time 7.27 h, and incubation temperature 43.3°C.

The study investigated the combined treatment of edible coatings and osmotic dehydration (OD) of pineapple samples. Pineapple samples were coated with 0.5% to 5.0% (w/v) sodium alginate solution by dipping for 60 s and 120 s and then dried at 50C for 10 and 40 min. OD in sucrose solution was carried out for coated and uncoated samples and water loss (WL), solid gain (SG), performance ratio (PR) and weight reduction (WR) were measured. There was a difference of 13.76 (g/100 g fresh sample) in the rates of WL between its highest and lowest value. The lowest value of 6.15 (g/100 g fresh sample) of SG and the highest value of PR of 7.32 was observed in the sample dipped in coating solution of 2% concentration for 120 s followed by drying for 40 min. WL increased whereas SG decreased up to a certain level of concentration of coating solution. PRACTICAL APPLICATIONS The treatment of coating may provide a solution to the problem of solid gain without affecting water removal during osmotic dehydration. The application of coating before osmotic dehydration (OD) will help in retaining nutrients and flavor than those without coating. The coated osmotically dehydrated fruits after rehydration can be added in ice cream, yogurt and confectionary products. Limited information is available in the literature combining coating with OD of fruits. Results of this study will be helpful in exploring the application of coating in pineapples. The combination of coating and OD may provide a practical method for the preservation of pineapple with better quality characteristics.

Response surface methodology was employed to optimize the incubation temperature (36.6-53.40C), incubation time (0.95-11.05 h) and enzyme concentration (0.16-0.84 mg/100 g guava pulp) on ascorbic acid retention, clarity, viscosity and color (L value) of guava juice. A central composite rotatable design was used. Significant regression models describing the changes of ascorbic acid, clarity, viscosity and color with respect to the independent variables (enzyme concentration, temperature and incubation time) were established with the coefficient of determination, R 2 , greater than 0.8. The results indicated that incubation temperature was the most significant (P < 0.01) variable in ascorbic acid retention, changes in clarity and color, whereas the incubation time showed the most significant (P < 0.01) effect on the viscosity of juice. The compromised optimum condition obtained by numerical integration for clarifying guava juice were: incubation temperature 45.35C, incubation time 7.23 h and enzyme concentration 0.70 mg/100 g guava pulp with ascorbic acid 77.71 mg/100 g, clarity 34.54% transmittance, viscosity 1.24 cps and color (L value) 23.33.

Allyl isothiocyanate (AITC), which has the potential to be used as flavoring, antibacterial, antifungal, antifermentative and antibrowning agent in food industry, was extracted from the pretreated MM by distillation technique. The mustard meal was analyzed for the proximate composition and the metals Fe, Mg and Zn. At the optimum pretreatment conditions of temperature 60 °C, time 120 min and pH 4.5, the effect of fractional distillation, mesh size and different additives was studied. Considerable effect of mesh size was observed, as the mesh size was decreased from 1,690 to 400 μm, the allyl isothiocyanate content was increased from 99.15 to 337.11 mg/100 ml. Addition of magnesium chloride (0.05 g/l to 0.2 g/l) and L-ascorbic acid (1 g/l to 5 g/l) increased allyl isothiocyanate from 257.79 to 317.28 mg/100 ml and 316.77 to 396.60 mg/100 ml respectively whereas the addition of the magnesium chloride and L-ascorbic acid in combination did not affect the AITC extraction rate as compare to their addition in single effect.