MSc

The study entitled “Optimization of process variables for osmo-air dehydrated Nendran banana (Musa spp.)’’ was conducted at Department of Processing Technology, College of Agriculture, Vellayani, during 2013-15 with the objective to standardize different process variables like fruit slice shape and thickness, osmotic solution concentration and immersion time for osmo-air dehydration of Nendran banana and to optimise the conditions suitable for better mass transfer kinetics.
Optimally ripened nendran banana (cv. Kaliethan) sliced into three shapes viz. long (5cm), round and ring of thickness 5, 10 and 15 mm each were osmosed in sugar syrup of 50, 60 and 70⁰ B concentration with an immersion time of 40, 60 and 80 minutes. Osmosed fruit slices were dried in cabinet drier at 50⁰ C till it attained moisture content of 171 % and analysed for physical, nutritional and sensory qualities. Observations on mass transfer, physical and nutritional parameters were statistically analysed using Response Surface Methodology (RSM) and response surfaces were fitted using SAS software (ver 9.3).
Mass transfer characters viz., solid gain, water loss, weight reduction and ratio of water loss to solid gain increased with increase in concentration of osmotic solution, thickness of slices and duration of immersion time irrespective of fruit shapes. Nutritional parameters of osmosed nendran banana exhibited an increase in total soluble solids, reducing sugars, total sugars with increase in thickness, concentration and time of immersion and a decreasing trend in acidity and vitamin C in all the three shapes. During drying water loss, weight reduction, drying rate and rehydration ratio decreased with increase in thickness and it increased with concentration and time of immersion. Shrinkage (%), browning index and textural qualities like cutting force and cutting energy also increased. Quadratic regression equation models were developed for all the responses with R2 > 90 %. Predictive model for water loss of longitudinally sliced nendran banana is WL= -7.01+8.77X1+6.52X2+3.57X3-0.91X11-0.89X22-0.036X33+0.20X1X2+0.29X1X3-0.68X2X3 where X1 is thickness, X2: concentration and X3: time of immersion and coded as X1=thickness/5, X2= (concentration-40)/10, X3=(Time-20)/20. Estimated minimum water loss for osmosed longitudinal slices was 15.14 % at thickness 5.54 mm, concentration 56.94 ⁰B , immersion time 53.26 minutes whereas estimated maximum water loss of 29.38 % was obtained for slices with thickness 14.09 mm, concentration 62.38 ⁰B and immersion time 70.41 minutes.
Based on sensory analysis, ten best treatments were selected and stored at room temperature for six months after packaging in 200 gauge polypropylene and analysed at monthly interval for nutritional, physical and sensory qualities. During storage, increase in moisture content (17.51 to 24.61 %), reducing sugar (44.95 to 51.19 %) and browning index (148.29 to 165.60) were observed where as acidity (1.71 to 1.12 %), total sugars (55.91 to 50.65%), vitamin C (27.85 to 27.73 mg/100 g) and rehydration ratio (1.82 to 1.35%) decreased. Textural qualities viz. cutting force and cutting energy increased from 34.73 to 41.76 N and 31.80 to 39.13 Ns respectively during storage. Sensory qualities of the product decreased slightly towards the end of storage and no microbial growth was found till the end of storage.
Second order response surface models were developed for mass transfer, drying and nutritional parameters of osmo-air dehydrated nendran banana. Slices of 5 to 10 mm thickness, 50 to 60⁰ B concentration and 50 to 60 minutes of immersion time were the optimized parameters for longitudinal and round slices whereas it was 5 to 8 mm, 50 to 55⁰ B and 40 to 50 minutes for ring shaped slices. Five and 10 mm thick rings of ripe nendran banana followed by 5 mm round slices osmosed in 50 ⁰B sugar syrup for 40 minutes were highly acceptable for developing good quality osmo dehydrated products. The products packaged in 200 gauge polypropylene were acceptable and microbiologically safe up to six months when stored at room temperature.