Impact of Postharvest Operations on Rice Grain Quality: A Review

Abstract

Postharvest operations, such as drying, storage, and milling, have been used to ameliorate the aging of rice grains and to achieve and maintain desirable rice grain quality, and thus play a key role in determining rice commercial quality and value. This review summarizes publications from the past decade and outlines the evidence supporting attribution of grain quality changes induced by postharvest processes to changes in the physical properties and chemical composition of the rice grain (starch, protein, lipids, and antioxidants). Rice drying mainly affects rice milling quality as rice kernel fissuring that may occur during drying leads to head rice yield reduction. Rice grain aging occurring during storage is inevitable and responsible for the changes in rice appearance, milling, eating, cooking, and nutritional quality. As milling significantly changes the chemical composition of rice by removing protein‐ and lipid‐rich bran layers, milling can alter the aging process of rice and also affect rice appearance, eating, and sensory quality, but mainly affects the nutritional quality. Therefore, drying methods, storage conditions, and milling methods warrant further research to achieve and maintain the desired rice grain quality. This review may contribute to better understanding of the impacts of postharvest processes on rice grain quality, and provide insights into potential improvements in these practices for rice production and utilization in the whole rice industry.

Multiple Mycotoxins in Kenyan Rice

“…In Kenya, approximately 10% of the grain is reported to be broken during milling [3]. Kernel breakage caused by poor postharvest handling of kernel and grains could increase infection and exacerbate fungal contamination [72].…”

Room Temperature in Scientific Protocols and Experiments Should be Defined: a Reproducibility Issue

“…Rice (Oryza sativa L.) grains stored for 6 months at 40 • C showed lower bound phenolic content and cooking time than grains stored at 16, 24 or 32 • C, although this depended on the cultivar [11]. When air becomes dry, caused by a high ratio of temperature to RH, rice grain quality is negatively impacted [12]. In a study on the influence of hyperbaric storage on bacterial (Bacillus subtilis) endospore growth in different matrices, RT was referred to as 'variable/uncontrolled' and defined as a wide range (16-24 • C) [13].…”

Transição vítrea e propriedades tecnológicas na secagem e temperagem de grãos de arroz em casca

“…The drying with average air temperature of 55° C and tempering of 240 min led to head rice yield (HRY) equivalent (p < 0.05) to that of the drying at average temperature of 30° C. Thus, it was observed that the higher the drying temperature employed, without proper tempering treatment, the greater the incidence of fissured grains and broken grains, and consequently, the lower the head rice yield (HRY). Rough rice grains subjected to drying temperatures above the glass transition temperature, without proper tempering treatment, do not resist high gradients of temperature and vapor pressure, which damage their physical integrity (TONG et al, 2019). Dong et al (2010) observed that after drying of rough rice (short grains), the tempering for 120 min eliminated about 80% of the moisture gradient created, which was an important factor in the formation of cracks and subsequent broken of grains.…”