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

Abstract

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.

Amino Acids in Rice Grains and Their Regulation by Polyamines and Phytohormones

“…In the ripe grain (caryopsis) of rice, there are 20 main amino acids, including eight essential amino acids that cannot be synthesized by humans and animals, namely Lys, threonine (Thr), methionine (Met), tryptophan (Trp), phenylalanine (Phe), isoleucine (Ile), leucine (Leu), and valine (Val) [2,5,21]. Among them, Lys, Thr, and Met are considered as the first, second, and third most restrictive essential amino acids in rice, respectively.…”

“…Amino acids are not only basic constituent units of proteins, but also act as metabolites/metabolic intermediates, enhancing plant growth and development as well as responding to various stresses [1,2]. Amino acids in the grains of cereal crops are important nutrition sources for both humans and animals [3][4][5]. Malnutrition caused by the insufficient intake of amino acids, especially the essential amino acids that humans and livestock are unable to carry out by de novo biosynthesis, is a serious problem around the world.…”

Effects of soaking duration and incubation conditions on GABA biosynthesis in MangBuk brown rice of Vietnam

“…These biofunctional components exist mainly in the germ and bran layers, most of which are removed by polishing or milling. In germinated grains, hydrolytic enzymes are activated and they decompose starch, non-starch polysaccharides, and proteins, which leads to an increase in oligosaccharides and amino acids (Patil & Khan, 2011;Albarracin et al, 2019). The decomposition of high molecular weight polymers during germination leads to the generation of bio-functional substances and the improvement of organoleptic qualities due to the softening of texture and increase in flavour.…”

“…Manufactured germinated rice is mostly sold in dried form (the drying does not affect the superior nutritional value accumulated from germination), which looks very similar to ordinary brown rice. The goal of the drying process is to prolong the shelf life of germinated rice (Albarracin et al, 2019). Compared to other rice varieties, germinated brown rice offers considerable health benefits, thanks to its increased amounts of γ-aminobutyric acid (GABA), dietary fibre, inositols, ferulic acid, phytic acid, tocotrienols, magnesium, potassium, zinc, γ-oryzanol, and prolylendopeptidase inhibitor.…”

The novel homologue of the human α‐glucosidase inhibited by the non‐germinated and germinated quinoa protein hydrolysates after in vitro gastrointestinal digestion

“…Lots of functional properties and beneficial effects of quinoa have been attributed to its protein fractions. To improve the quality of the protein, the peptides should be released during proteolysis and through processes such as germination and gastrointestinal digestion (Aguillón‐Osma et al., 2019; Albarracín et al., 2019). Many researchers have reported an improvement in antioxidant, adipogenesis inhibitory activity, antimicrobial, and nutritional properties of quinoa after the enzymatic hydrolysis (Galante et al., 2020; Mudgil et al., 2019).…”