Germination Time Dependence of Bioactive Compounds and Antioxidant Activity in Germinated Rough Rice (Oryza sativa L.)

Health-promoting germinated rice and value-added foods: a comprehensive and systematic review of germination effects on brown rice

Over the last 30 years, thousands of articles have appeared examining the effects of soaking and germinating brown rice (BR). Variable germination conditions and methods have been employed to measure different health-beneficial parameters in a diverse germplasm of BR. Research results may therefore appear inconsistent with occasional anomalies, and it may be difficult to reach consensus concerning expected trends. Herein, we amassed a comprehensive review on germinated brown rice (GBR), attempting to codify 133 peer-reviewed articles regarding the effects on 164 chemical parameters related to health and nutrition in BR and in value-added food products. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-2020) approach was used to direct the flow of the literature search. A pair-wise comparison t-test was performed to deliver an overall approach indicating when a given compound has been found to significantly increase or decrease through germination, which was grouped into GABA and polyamines, γ-Oryzanol and phytosterols, phenolic compounds, vitamins, proteins and amino acids, starchy carbohydrates, free sugars, lipids, minerals and phytic acid. This resource will stimulate interest in germinating rice and optimistically help increase both production and consumption of highly nutritious, health-beneficial rice with pigmented bran.

Functional Properties of Polyphenols in Grains and Effects of Physicochemical Processing on Polyphenols

Phenolic compounds are important products of secondary metabolism in plants. They cannot be synthesized in the human body and are mainly taken from food. Cereals, especially whole grains, are important sources of dietary polyphenols. Compared with vegetables and fruits, the content and biological activities of polyphenols in cereals have long been underestimated. Polyphenols in whole grains are non-nutritive compounds, which are distributed in all structural areas of cereal substances, mainly phenolic acids, flavonoids, and lignans. In recent years, the health effects of whole grains are closely related to their phenolic compounds and their antioxidant activities. Now, different physicochemical processing treatments and their effects have been summarized in order to provide the basis for promoting the development and utilization of food. The various functions of whole grains are closely related to the antioxidant effect of polyphenols. As the basic research on evaluating the antioxidant effect of active substances, in vitro antioxidant tests are faster and more convenient.

Modification of nutritional properties of whole rice flours (Oryza sativa L.) by soaking, germination, and extrusion

Modifications of nutritional properties (amino acids, available lysine, protein digestibility, fatty acids, fiber, inositol phosphate (IPs), free and bound phenolics, and antioxidant properties) of whole rice ingredients processed by soaking, germination, and/or extrusion cooking were evaluated. Soaking and germination reduced proteins by lixiviation and hydrolysis, respectively. Lysine was the limiting amino acid. Polyunsaturated fatty acids increased after germination. Protein digestibility was 100% for germinated rice, decreased to 75% after the extrusion process. Fiber content decreased around 73% after the extrusion of soaked and germinated flours. Soaking-extrusion combined processes produces >50% IPs reduction. Germination-extrusion produced flours with the highest antioxidant capacity (54 µmol trolox g^-1 ), which was in accordance with the highest content of free and bound phenolics (66 and 69 mg GA 100 g^-1 , respectively). Grain treatments changed nutritional properties of flours resulting in low antinutrient whole grain ingredients, which could be used to develop whole grain-based foods. PRACTICAL APPLICATIONS: Phytic acid (PA) is an antinutrient having negative effects on mineral bioavailability and protein digestibility. There are processes such as soaking, germination, and extrusion, which alone or combined can decrease PA. However, nutritional composition and functionality of flours can change. We observed PA was highly reduced by soaking or germination combined with extrusion and antioxidant capacity and phenolic content increased in germinated and germinated-extruded flours compared to the other treatments. These modified whole grain rice flours low in anti-nutrients could be used in the production of expanded products or pre-cooked ingredients to develop whole grain based foods nutritionally improved.

Factors influencing antioxidant compounds in rice

Epidemiological and clinical studies suggest that the additive/synergistic effects of several bioactive compounds are responsible for the health benefits of rice. Among the leading contenders are phenolic acids, flavonoids, anthocyanins, proanthocyanidins, tocotrienols, tocopherols, λ-oryzanol, and phytic acid, which all possess strong antioxidant activities in vitro. In this review, data related to health effects of rice antioxidants using cultured cells, rodents and humans models are first summarized. The evidence is strong that consumption of rice tocotrienols translates into improved health outcomes. Current research, however, does not strongly support the health-promoting effects of rice tocopherols and phenolic acids. The crucial limitations in studies using rice flavonoids, anthocyanins, proanthocyanidins, λ-oryzanol and phytic acid appear to be the appropriateness of the substance tested (i.e., purity), and the scarcity of animal and human interventions. In a second part, rice antioxidants are reviewed with an emphasis on their composition and contents. Taking into account the bioavailability of these compounds, it is evident that a number of factors affect the antioxidant composition of rice, making it difficult to estimate dietary intake. Before harvest, factors including soil type, atmospheric CO₂, chemical inputs, temperature, and degree of ripening are important. After harvest, rice is subjected to processing methods that include drying, parboiling, storage, irradiation, milling, stabilization, soaking, germination, fermentation, boiling, steaming, roasting, baking, and extrusion. Quantitative knowledge about the effects of these processes is summarized in this review. Surprisingly, a high level of agreement was found among study results, which could be useful in manipulating the growing and processing techniques of rice grains to facilitate efficient and safe consumption of antioxidant compounds.