Effects of malting conditions on enzyme activities, chemical, and bioactive compounds of sorghum starchy products as raw material for brewery

Abstract

Two cultivars of sorghum (red, RS and white, WS) were germinated at 25 or 30°C for 1, 2, or 3 days and were evaluated regarding enzyme activities (diastatic power: DP, b-amylase), chemical compounds (total starch, damaged starch, glucose, free amino acid), and bioactive compounds (free phenolic compounds: FPC and g-aminobutyric acid:GABA). For WS and RS (on third germination day at 30°C), DP was 11.3 AE 1.4 and 10.8 AE 1.3°DP, b-amylase activity: 33.0 AE 0.9 and 71.1 AE 0.7 UBetamyl/g d.b., respectively, while at 25°C, DP was 6.1 AE 0.7 and 18.0 AE 1.1°DP, b-amylase activity: 9.3 AE 0.5 and 57.8 AE 0.3 UBetamyl/g d.b., respectively. Starch degradation, free amino acids, and free glucose content increased during germination, and depended on cultivar, germination time and temperature. The hydrolysis of the protein matrix influenced the release of starch granules, which were more accessible to amylolytic action. FPC and GABA levels were higher after grain germination and depended on sorghum cultivar and germination temperature. Germination at 30°C for 3 days represented the most suitable conditions for obtaining good bio-functional sorghum malt.

Whole Grains and Phenolic Acids: A Review on Bioactivity, Functionality, Health Benefits and Bioavailability

“…An increase in the nutritive value, total phenolics content, dietary fiber content, and radical scavenging activity (DPPH) of the wheat flour with the increase in germination time of wheat grains was reported in several studies [ 196 , 197 , 198 ]. Therefore, soaking and germination have been recommended to enhance the nutritional value and potential functional effects of cereal grains and cereal-based products [ 199 , 200 ].…”

Changes in phenolics, γ‐aminobutyric acid content and antioxidant, antihypertensive and hypoglycaemic properties during ale white sorghum (Sorghum bicolor (L.) Moench) brewing process

“…During the first steps, GABA level keeps constant (~1.5 mg per 100 g s.s.), but it increased after the first fermentation (FF) step to ~15 mg per 100 g s.s., and remained at the same level in SB. It is known that malting of a cereal increases GABA content during steeping and germination due to seed stress conditions (Garzón et al ., ). Moreover, yeast ( Saccharomyces cerevisiae ) synthesizes and accumulates GABA on vacuoles (Bach et al ., ).…”

“…White sorghum cultivar (341 × 120) was obtained from Nuseed S.A., VenadoTuerto, Santa Fe, Argentina. Sorghum grains were malted and milled as described previously (Garzón et al ., ). Briefly, 6 kg grains were steeped in tap water (3:1) for 24 h at room temperature (25 °C).…”

Aptitude of sorghum ( Sorghum bicolor (L) Moench) hybrids for brewery or bio‐functional malted beverages

“…Part of water soluble FPC leach during steeping, since phenolics are primary located in pericarp and testa, thus water‐extractable FPC decrease respect to native grains. However, after germination, water‐extractable FPC increased (Garzón et al, ). Dicko et al () found germination decreased or increased total phenolic content according to sorghum cultivar.…”

“…It is known the cultivar influences directly biochemical properties of malt (Dicko, Gruppen, Traore, van Berkel, & Voragen, ), and a good quality grain is fundamental to produce acceptable food products from malted sorghum. In a previous study, Garzon, Torres, and Drago () found optimal malting conditions to produce sorghum beer (germination at 30°C for 3 days), or biofunctional sorghum beverages (germination at 25°C for 3 days). As far as we know, there is no report about the influence of chemical composition of native or malted sorghum grains on the aptitude to produce functional beverages.…”