Improvement of structure and cooking quality of brown rice using ultrasonic and enzymatic treatments

Abstract

Brown rice (Oryza sativa L.) was subjected to ultrasonic treatment (UT) and three enzymatic treatments (ET) with cellulase, glucoamylase and α‐amylase. All treatments changed pasting properties of brown rice flour and structure of brown rice grain surface, but only UT and α‐amylase treatment (AT) significantly affected starch granules inside the grain. During cooking, water uptake and volume expansion of UT brown rice were higher than those of ET. Both UT and ET decreased hardness of the cooked brown rice from 206.05 N to 192.22–154.02 N in which the AT cooked rice was the softest. Although UT reduced hardness and increased volume expansion, the brown rice from AT had the highest liking score. Principle component analysis also visualized the preferable brown rice from AT. Therefore, AT was considered to potentially become a novel technology for development of high‐quality brown rice. Practical applications Brown rice is normally soaked in water before cooking. Modifying the structure of brown rice by ultrasonic or enzymatic treatment could improve water uptake, volume expansion and texture of the cooked brown rice. Therefore, enzymatic treatment by α‐amylase was recommended to produce the soften brown rice without soaking before cooking.

Impact of ultrasonic treatment on rice starch and grain functional properties: A review

“…Similar observations were reported by Zhang et al [51] ; the enhanced water absorption of UT brown rice effectively decreased from 28.7 mins to 24.3 mins with enzymatic treatment only and further reduced to 22.3 mins with ultrasonic and enzymatic treatments. Moreover, an increase in water uptake of UT Thai brown rice [84] , [73] reduced the cooking time of Shanlan rice after UT [88] . Volume expansion is also affected by ultrasonication; Dang et al [73] reported an increase in volume expansion ratio of brown rice (2.83 ± 0.24 to 3.33 ± 0.00) after ultrasonication.…”

“…(A, C) Brown rice; (B, D) milled rice. Sonication conditions: (a) 40 kHz, 150 W, 30 mins, 30 °C [84] ; (b) 40 kHz, 300 W, 10 mins, 4 °C [53] ; (c) 16 kHz, 2 kW, 30 mins, 55 °C [50] ; (d) 53 kHz, 5 mins, 55 °C [52] . Reprinted with permission.…”

“…Table 3 summarizes the impact of ultrasonication on rice thermal, crystalline, and pasting properties. In terms of pasting properties, an increase in the peak and final viscosities are observed in isolated starch, even if different UT conditions are applied in the rice samples [50] , [51] , [71] , [72] , [77] , [84] . The elevated peak viscosity is caused by the softening of the rice starch matrix resulting in an easier rupture of starch during gelatinization.…”

Effects of ultrasonic and enzymatic treatment on physical and chemical properties of brown rice

“…The major loss in these chemical components could be caused by the soaking of brown rice in water and buffer solution during ultrasonic and ETs. Amylose content was reported in Dang et al (). Amylose content was reduced significantly in case of GT and AT, due to the starch hydrolysis action of these enzymes.…”

“…The major loss in these chemical components could be caused by the soaking of brown rice in water and buffer solution during ultrasonic and ETs. Amylose content was reported inDang et al (2018).…”