Effects of degree of milling on nutritional quality, functional characteristics and volatile compounds of brown rice tea

Lei Zhou; Yong Sui; Zhenzhou Zhu; Shuyi Li; Rui Xu; Junren Wen; Jianbin Shi; Sha Cai; Tian Xiong; Fang Cai; Xin Mei

doi:10.3389/fnut.2023.1232251

Effects of degree of milling on nutritional quality, functional characteristics and volatile compounds of brown rice tea

Front Nutr. 2023 Aug 24:10:1232251. doi: 10.3389/fnut.2023.1232251. eCollection 2023.

Authors

Lei Zhou^{1

2}, Yong Sui¹, Zhenzhou Zhu², Shuyi Li², Rui Xu^{1

2}, Junren Wen¹, Jianbin Shi¹, Sha Cai¹, Tian Xiong¹, Fang Cai¹, Xin Mei¹

Affiliations

¹ Key Laboratory of Agro-Products Cold Chain Logistics, Ministry of Agriculture and Rural Affairs, Institute of Agro-Products Processing and Nuclear-Agricultural Technology, Hubei Academy of Agricultural Science, Wuhan, China.
² School of Modern Industry for Selenium Science and Engineering, Wuhan Polytechnic University, National R&D Center for Se-Rich Agricultural Products Processing, Hubei Engineering Research Center for Deep Processing of Green Se-rich Agricultural Products, Wuhan, China.

Abstract

This study investigated the effects of rice preparation using different degrees of milling (DOM) from 0% to 13% on the nutritional composition, functional properties, major volatile compounds and safety of brown rice tea (BRT). We found that 2% DOM reduced 52.33% of acrylamide and 31.88% of fluorescent AGEs. When DOM was increased from 0% to 13%, the total phenolic content (TPC) of brown rice tea decreased by 48.12%, and the total flavonoid content (TFC) and condensed tannin content (CTC) also decreased significantly, with the smallest decrease at 2% DOM. In addition, the inhibitory activities of α-amylase, α-glucosidase and pancreatic lipase as well as the antioxidant activity also decreased gradually. Analysis by electronic nose and gas chromatography-mass spectrometry (GC-MS) showed that alkanes, furans, aldehydes, pyrazines and alcohols were the major volatiles in BRT, with 2% DOM having the greatest retention of aroma compounds. An orthogonal partial least squares discriminant analysis (OPLS-DA) and VIP score (VIP > 1 and p < 0.05) analysis were used to screen 25 flavor substances that contributed to the differences in BRT aroma of different DOMs. These results suggest that 2% milled BRT can improve safety and palatability while maximizing the retention of flavor compounds and nutrients. The findings of this study contribute to an enhanced understanding of the dynamics of changes and preservation of aroma compounds and nutrients present during the processing of BRT.

Keywords: OPLS-DA; aroma compounds; brown rice tea; degree of milling; nutrients.