Short title: Sorghum grain type and wort physico-chemical and sensory quality
ABSTRACTTo determine the most suitable types of sorghum for whole grain adjunct in lager beer brewing, 14 cultivars of five different types: white tan-plant, white not tan-plant, red non-tannin, white tannin (Type II), and red tannin (Type III) were evaluated. The effects of grain type on wort physico-chemical and sensory quality with raw grain and malt plus commercial enzyme mashing were assessed. Tannin content correlated significantly and negatively with wort extract and fermentable sugars (p<0.001) and free amino nitrogen (FAN) (p<0.1). This is attributable to inactivation of the exogenous enzymes by the tannins during the mashing process. However, the Type II tannin sorghums had wort quality attributes closer to the non-tannin sorghum types, probably due to their relatively low tannin content (≤1%). Malting gave a great improvement in wort extract, fermentable sugars and FAN but substantially influenced wort sensory properties in terms of higher sourness, bitterness and astringency as well as the expected more malty flavour.Worts from raw red non-tannin sorghums were similar to those of white tan-plant sorghums in both physico-chemical and sensory quality. Thus, red non-tannin sorghums, in view of their better agronomic quality, have considerable potential as whole grain adjunct in lager brewing.
.Running title: Tannin inactivation in milled sorghum grain with dilute NaOH 1 Highlights Steeping milled Type III tannin sorghum in NaOH solution reduces tannin content NaOH treatment substantially reduces α-amylase inhibition by the tannins Tannin polymerization was found to be the mechanism of inactivation NaOH treatment could enable use of Type III tannin sorghum in bioethanol production 2
ABSTRACTSteeping milled sorghum in up to 0.4% NaOH was investigated as a method of tannin inactivation. NaOH steeping substantially reduced assayable total phenols and tannins in both Type III and Type II sorghums and with Type III sorghum caused a 60-80% reduction in α-amylase inhibition compared to a 20% reduction by water steeping. NaOH treatment also reduced starch liquefaction time and increased free amino nitrogen. Type II tannin sorghum did not inhibit α-amylase and consequently the NaOH treatment had no effect. HPLC and LC-MS of the tannin extracts indicated a general trend of increasing proanthocyanin/procyanidin size with increasing NaOH concentration and steeping time, coupled with a reduction in total area of peaks resolved. These show that the NaOH treatment forms highly polymerised tannin compounds, too large to assay and to interact with the α-amylase. NaOH pre-treatment of Type III sorghums could enable their utilization in bioethanol production.
Processing functionality in terms of fermentability and nutritional characteristics of Mahewu (a sorghum‐based nonalcoholic beverage product) supplemented with different proportions of Bambara groundnut (BGN) (80:20 and 70:30, respectively) was investigated to develop a sorghum‐based beverage product with improved nutritional quality. Sorghum‐BGN Mahewu blends showed a rapid reduction in pH and significantly (P < 0.05) lower final pH (4.3) after 24 hr compared to the control (pH 5.1) (100% Sorghum Mahewu). With total titratable acidity (TTA), sorghum–BGN Mahewu blends had significantly higher final TTA (0.7%) than control (0.4%). Sorghum–BGN Mahewu blends had higher protein and crude fiber contents (up to 7.7% and 7.9%, respectively) than control (6.1% and 5.7%, respectively). In general, sorghum Mahewu supplemented with BGN did not show substantial increase in mineral and individual amino acid contents after fermentation compared to the control, possibly due to increase in tannin content with BGN supplementation. Fermentation significantly (P < 0.05) reduced phytate content by more than 90% in sorghum Mahewu supplemented with BGN when compared to the control (28% reduction). Importantly, BGN supplementation improved the level of some essential amino acids such as threonine, methionine, phenylalanine, isoleucine, leucine, histidine, and lysine. Therefore, supplementation with BGN can potentially improve the nutritional quality of sorghum Mahewu but modification in processing procedure is required to effectively improve the nutritional quality of sorghum–BGN blends.
Practical Application
This research work has direct application in addressing problem of malnutrition, as well as improving utilization of indigenous food crops in commercial food processing. This is one of the practical approach to address food insecurity that is prevalent in most African countries.
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