Quality changes in HTST processing of rice parboiling

Abstract

Paddy soaked to saturation level, when treated at a high temperature for a short time in a mechanical sand roaster is parboiled and dried in a single pass of 47 s duration. The extent of drying depends on the sand temperature. The sand temperature is critical as it decides the associated quality changes in the milled rice. Even at a sand temperature of 125"C, paddy could fully be parboiled but with mild effect. The parboiling became severe at high temperatures. Roasting the soaked paddy at 250"C, reduced the cooking time of the resultant milled rice. A sand temperature of 125-150°C was considered suitable for producing normal parboiled rice by this technique.

Mild Hydrothermal Treatment for Improving Outturn of Basmati Rice

“…Consumers may not prefer very tough rice. Other previous studies have also shown that a majority of consumers prefer whiter rice products Pillaiyar [4] and Chattopadhyay and Kunze [16] reported that the minimum level of hydrothermal treatments for Brazos variety was 270 min soaking at 65 • C and 5 min steaming at 103.51 kPa. Miah et al [12] and Behra and Sutta [17] reported that a minimum hydrothermal treatment for long grain rice variety (BR4), of about 45-min soaking at 80 • C followed by steaming for about 10 min under 1 atmosphere excess pressure is necessary to improve all the required qualities of rice for better consumer preference.…”

“…Champa et al [13] reported that reduction of grain breakage during milling operation and increasing of head rice yield is due to long soaking and steaming durations, which caused several physicochemical changes occurring in the rice caryopsis. Pillaiyar [4] reported that non-treated raw rice was soft and parboiled rice was hard, the hardness increasing with the degree of heat treatment such as steaming pressure and steaming duration during parboiling. Ali and Bhattacharya [14] reported that the high-pressure steaming brings about complete gelatinization of the grain up to the center, even at a low soaking moisture level.…”

“…Water and heat are the two main elements in the hydrothermal process, which is the main process of parboiling. It can be achieved through a variety of methods that differ basically in the intensity of the heat of hydrothermal treatment [2][3][4][5]. Parboiling of rice causes physical and chemical modifications in the grain, leading to favourable changes such as easier shelling, higher head rice yield, fewer broken grains, increased resistance to insects, firmer cooked rice texture, less solids loss during cooking and washing, better retention of nutrients (e.g., proteins, vitamins and minerals) and higher oil content in the bran [2][3][4][5].…”

Process of parboiling rice by microwave-assisted hot air fluidized bed technique

“…The starch gelatinization with no retrogradation is specifically found, unlike to the wet heat process, because of the simultaneous rapid loss of water from the paddy during conduction heating was studied by Mahanta and Bhattachaya [2]. Pillaiyar et al [3] reported that the roasting sand at temperature of 125 o C could get the fully PB but with mild effect. The parboiling became severe at high temperatures.…”