Fortification of zinc in a parboiled low‐amylose rice: effects of milling and cooking

Abstract

BACKGROUND Rice is a staple diet for many people, however, it is not a good source of micronutrients. The process of parboiling induces several desirable changes in rice: it improves the retention of available micronutrients, and in the case of low‐amylose varieties it eases the cooking requirement. During parboiling of brown rice, when soaking is conducted in micronutrient‐rich solutions, it affects fortification. This study is aimed at examining the suitability of the method of zinc fortification by a brown rice parboiling process in a low‐amylose rice. RESULTS Application of the method of zinc fortification by a brown rice parboiling process increased the zinc content in unmilled rice. Milling caused a reduction in zinc content per gram of grain, indicating a high concentration of zinc at the outer layer. Both milled and unmilled rice could retain more than 86% of zinc upon cooking. Changes in colour values in uncooked rice, due to zinc fortification, were non‐significant at P ≤ 0.05. Rehydration of zinc‐fortified rice at 60 °C for 25 min yielded hardness values similar to that of its cooked form. CONCLUSION The method of zinc fortification by brown rice parboiling is a pragmatic way to produce zinc‐fortified parboiled rice to combat zinc deficiency with a reduced cooking requirement from a low‐amylose rice variety. © 2019 Society of Chemical Industry

Studies on in vitro bioavailability and starch hydrolysis in zinc fortified ready-to-eat parboiled rice (komal chawal)

“…Raw rice has A-type starch, which in parboiled rice gets converted into B-type or/and V-type or mixed pattern (Prasert and Suwannaporn 2009). This was also observed in our previous study by XRD analysis (Wahengbam et al 2019b). The presence of A-type starches in raw rice attributes to higher hydrolysis rate than the parboiled rice.…”

“…This might be due to loss of accumulated Zn in the outer surface of kernels (aleurone layer) mainly. Whereas, the less % reduction of Zn in case of parboiled rice soaked in more concentrated Zn solution might be due to diffusion of Zn ions beyond the aleurone layer (Wahengbam et al 2019b).…”

“…The codings of the samples for Zn fortified and unfortified rice are given in Table 1. The content of Zinc in all fractions of rice before and after fortification has been estimated in our previous work (Wahengbam et al 2019b) and values are included in Table 1. The Zn fraction retained in the supernatant after the in vitro simulation digestion is the bioaccessible form of soluble which is potentially available for absorption in the intestinal cells.…”

“…The products thus obtained were milled separately for 30 s (4% degree of milling) and 60 s (8% degree of milling) by using a rice polisher (RTE-08, A GRAIN, India). Before the in vitro study, the unfortified and fortified dried parboiled rice were rehydrated by soaking in water at 60°C for 25 min to obtain the desired hardness and adhesiveness of cooked condition (Wahengbam et al 2019b).…”

“…The product rehydrates in warm water to a texture soft enough for consumption on soaking for 20-25 min (Wahengbam et al 2019b). In the present study, chokuwa rice is used as a carrier for Zn fortification during the production of komal chawal by brown rice parboiling method instead of traditional paddy parboiling.…”