Effect of Presoaking on Textural, Thermal, and Digestive Properties of Cooked Brown Rice

Abstract

Cereal Chem. 86(1):100-105Brown rice kernels (japonica type) were soaked in water at different temperatures (25 or 50°C) before cooking to a moisture content of 20 or 30%. Soaked brown rice was cooked in either the soaking water (SW) or in distilled water (DW) (rice solids to water ratio 1:1.4). Color, texture, and in vitro digestive properties of the cooked rice were examined. When the soaking temperature was higher (50°C vs. 25°C), water absorption and starch leaching were greater. To reach 20% moisture, the rice required 1 hr of soaking at 50°C but 2 hr of soaking at 25°C. Both the moisture content of the soaked rice and the soaking temperature affected the texture of the cooked brown rice. Rice that attained 20% moisture content during soaking was harder and less adhesive when cooked compared with rice that attained 30% moisture cpontent. The rice soaked at 50°C was slightly softer but more adhesive when cooked than rice soaked at 25°C. The soaking temperature and moisture content of the rice kernels also affected the digestive properties of the cooked rice. The cooked brown rice that had attained 30% moisture before cooking was digested to a greater extent than rice that had attained 20% moisture. Even at equal moisture content, the rice soaked at the higher temperature (50°C) was digested more readily. It was assumed that the amount of soluble material leached during soaking differed according to the soaking temperature and moisture content, which subsequently affected the texture and digestive properties of the cooked brown rice. The rice cooked in its own soaking water was harder and more adhesive, had higher levels of resistant starch (RS), and exhibited smaller glycemic index (GI) values than its counterpart cooked with distilled water. This result indicated that the soluble material leached during soaking made the cooked rice harder and less digestible, perhaps due to interactions between these molecules and the gelatinized rice during cooking. 2 Corresponding authors. (Han)

Effect of presoaking high hydrostatic pressure on the cooking properties of brown rice

“…The smallest hardness (674 g) of soaked brown rice occurred at 40°C for 5 h. We observed that the soaking temperature played a very important role in the brown rice cooking process. Han and Lim (2009) revealed that the brown rice attained 20 % moisture content during soaking was harder than that of the rice which attained 30 % moisture content when cooked, which is consistent with our results.…”

Effect of soaking and single/two cycle high pressure treatment on water absorption, color, morphology and cooked texture of brown rice

“…Nowadays, due to changes in consumer life style and health awareness, brown rice is receiving increased interest as a source of not only energy but also several other healthy attributes (Mir et al 2016). Compared with white rice, brown rice is rich in several health beneficial nutrients such as dietary fiber, gamma-oryzanol (an active component of rice bran), antioxidants, essential amino acids, vitamins and minerals (Cui et al 2010;Han and Lim 2009). Despite its the high nutrient content, brown rice is not well accepted as white rice because of the rough and tough texture making it hard to chew (Chen et al 2012).…”

“…In order to obtain uniform water absorption and desired texture, it is a common practice to soak the brown rice in water before it is cooked (Han and Lim 2009). However, the simple soaking treatment takes a long time and hinders production efficiency in commercial practice.…”

Effects of Leached Amylose and Amylopectin in Rice Cooking Liquidon Texture and Structure of Cooked Rice

“…The starch molecules in rice are tightly distributed to form fascircular micella, which are unpenetrable to water molecules. During soaking and cooking, the AM and AP located near the surface of the rice could leach out into water at low temperature (Han and Lim, 2009). Along with temperature rise, water permeated into the partially crystallized AM and AP molecules in rice grains, also the starch grains started to absorb water and swell, the starch grains broke down to form unimolecule, and the doublehelix of AM was opened, then AM and AP in starch grains were leached gradually (Janeand Shen,1993).…”

“…After filling up the hollows， the appearance of cooked rice displays an uneven structure (Figure 6f). The leached AM in cooking water is relatively smaller and greater mobility than AP, which facilitated themselves entering into the hollows at the surface of the cooked rice (Han and Lim, 2009). When the water was finally boiled off, the leached short-chain AM began to migrate and entered into the hollows at the surface of the cooked rice.…”