Study on high temperature short time (HTST) hot air puffing of rice.

Hot air puffing is the simplest, hazard- and contamination-free, and quickest method, wherein grains are suddenly exposed to a high temperature short time (HTST) process to get puffed. In this study, the continuous hot air puffing system was developed, comprising of grain feeder, heating chamber, puffing chamber, cyclone separator, and recirculation pipe. The experiments were conducted using Central Composite Rotatable Design (CCRD), on pre-processed rice (cv. MTU 1010), with one pre-heating pass of 11.50 s at 150 °C. The results showed that the puffed rice can be produced optimally at a pre-fixed whirling air velocity of 4.75 (± 0.25) m/s, puffing air temperature of 260 °C and with a feed rate of 6500 g/h, resulting in final moisture content (% db), expansion ratio, puffing percentage (%), whiteness index, hardness (kg) and crispness (+ve peaks) as 3.71, 5.68, 95.87, 69.82, 32.12 and 89.81, respectively. Further study on increased time of preheating upto 46 s (4 passes) at 150 °C keeping all other puffing parameters unchanged, showed that final moisture content (% db), expansion ratio, puffing percentage (%), and whiteness index were further improved like final moisture content reduced upto 2.68% db and expansion ratio, puffing percentage, whiteness index increased upto 7.35, 99.58% and 87.76, respectively. Thus, the rice puffing using a continuous hot air puffing system can be accomplished using 4 pre-heating passes (accumulative retention heating time of 46 s) at 150 °C, puffed using a hot air puffing system with whirling velocity of 4.75 m/s at a puffing temperature and feed rate of 260 °C and 6500 g/h. [ABSTRACT FROM AUTHOR]