Effects of Germination Duration on Milling, Physicochemical, and Textural Properties of Medium‐ and Long‐Grain Rice

Abstract

Cereal Chem. 93(1):39-46Germinated brown rice is popular in Asia for its increased g-aminobutyric acid (GABA) content and sweeter and softer texture compared with conventional brown rice. However, most studies investigated germinated rice properties on medium-grain or aromatic rice. The objective of this study was to compare differences between a medium-grain (Jupiter) and a long-grain (Wells) rice under similar germination conditions on their milling, physicochemical, and textural properties over the course of germination. Rough rice was soaked in water at 25°C for 12 h and then incubated at 30-34°C for four germination durations. Wells had a higher breakage percentage and a greater weight decrease than Jupiter during germination. Wells had a significantly lower GABA content before germination and at the first two germination durations than Jupiter, but the GABA content in Wells significantly increased at the third germination duration to become significantly higher than that of Jupiter. There were no significant changes in gelatinization temperatures and pasting properties of germinated rice from both cultivars at different germination durations. The cooked rice hardness from Wells decreased at the longest germination duration, whereas Jupiter showed a more significant decrease in cooked rice stickiness from germination. The results demonstrate that the impacts of germination on physical, chemical, and textural properties of rice were affected by grain type and germination

Effect of Parboiling on Milling, Physicochemical, and Textural Properties of Medium‐ and Long‐Grain Germinated Brown Rice

“…The enthalpy values of amylose-lipid complex were similar to those reported by Newton et al (2011). The lack of significant differences in amylose-lipid complex melting between germination durations for both cultivars agrees with the previous study (Han et al 2016) and suggests that germination did not sufficiently alter amylose molecular size to change its interaction with lipids.…”

“…There were two endothermic transitions in parboiled germinated rice for both cultivars (Table III): retrograded amylopectin melting at a lower temperature and amyloselipid complex melting at a higher temperature. The lack of significant changes between germination durations for amylopectin retrogradation properties in both cultivars support the previous study (Han et al 2016) that germination did not significantly change amylopectin structure to result in different amounts and structures of retrograded crystallites. The greater proportion of amylopectin long branch chains in Wells not only contributed to its higher gelatinization temperatures but also was responsible for its increased retrogradation extent.…”

“…Jupiter had an overall higher pasting profile than Wells (Fig. These results support the previous study, in which a similar pasting profile was found in germinated rice from the same cultivar at different germination durations when conducted in silver nitrate (Han et al 2016). The pasting viscosities were significantly decreased after parboiling when compared with their germinated counterparts (Han et al 2016) owing to reduced starch waterbinding capacity after gelatinization, retrogradation, and interaction with protein and lipids, thereby decreasing swelling ability (Rao and Juliano 1970;Ali and Bhattacharya 1980;Soponronnarit et al 2006;Patindol et al 2008).…”

“…Upon parboiling the whiteness significantly decreased for both cultivars (P < 0.001), but their difference still remained, with Wells having higher whiteness values than Jupiter (Table II). The lower whiteness values in Jupiter samples were correlated with their higher soluble sugar contents (Han et al 2016). The lower whiteness values in Jupiter samples were correlated with their higher soluble sugar contents (Han et al 2016).…”

“…Before parboiling, germinated brown rice samples from Wells were generally higher in hardness and lower in stickiness than those from Jupiter when cooked (Han et al 2016). Before parboiling, germinated brown rice samples from Wells were generally higher in hardness and lower in stickiness than those from Jupiter when cooked (Han et al 2016).…”