OPTIMIZATION OF SPRAY DRYING PARAMETERS FOR PASSION FRUIT JUICE

Abstract

Passion fruit (Passiflora edulis v. flavicarpa) juice attracts consumer attention due to its unique flavor and aroma. The passion fruit juice has so many health benefits due to the presence of vitamins (riboflavin, vitamin C, vitamin A and niacin) minerals (potassium, calcium, phosphorous, and magnesium) and antioxidants (vitamin C, beta- carotene, and polyphenols). Kerala has all sets of climate and sufficient rain fall for cultivating passion fruit. The conventional preservation techniques viz. freezing and concentration was not adequate. Since passion fruit is highly perishable in nature, cold chain is essential to extend its shelf life. The poor processing and transportation facility in Kerala state hinders the cold chain. In this context, spray drying was found to be promising technology to preserve passion fruit juice for longer period at ambient temperature. Hence the aim of the study was to develop spray dried passion fruit juice powder. Maltodextrin and corn starch at 3:2 ratios was chosen as wall material. Passion fruit juice mixed with wall material at 15 %, 17.5 %, and 20 % w/v to prepare feed solution. For spray drying, the inlet air temperature set as (150 °C, 160 °C and 170 °C) and feed rate set as (8, 10, and 12 rpm). The Box- Behnken design of RSM (Design Expert software- Version 7.0. 0) was applied to optimize process parameters viz., wall material concentration, inlet air temperature and feed rate based on physico-chemical properties of the spray dried passion fruit juice powder. The optimized process conditions to obtain best quality passion fruit juice powder was 12 % maltodextrin, 8 % corn starch, inlet air temperature of 165 °C, feed pump speed of 12 rpm (0.83 ml/ h), outlet air temperature of 75 °C, blower speed of 1700 rpm and atomizer pressure of 2.5 kg/ cm 2 . The optimized powder sample possesses quality attributes of product yield (61.23 %), moisture content (1.62 %), titrable acidity (5.67 %), vitamin C (23.15 mg/100g), total difference in colour (20.37), pH value (6.5), CI index (4.11), hausner ratio (1.043), bulk density (0.513 g/cm 3 ), and true density (0.535 g/cm 3 ). Particle surface morphology and size of optimized passion fruit juice powder was analysed and estimated using scanning electron microscopy (SEM). Particles were observed as individual particles well separated from each other, with a spherical morphology, a smooth surface, and with likely uniform sizes. The particle size of the spray dried passion fruit juice powder varied from 53.87 µm to 80.39 µm. The optimally produced sample scored a sensory score of 7.91. The storage study was conducted using different packaging materials viz. aluminium laminated pouches and polypropylene pouches at various storage temperatures such as ambient and refrigerated. The spray dried passion fruit powder was safe to be store in aluminium laminated pouches of 150 microns thickness at ambient conditions for three months. The production cost of one kilogram of spray dried passion fruit juice powder was estimated as Rs. 1874/-.