Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2015
Publication Date: 2/2/2017
Citation: Liu, K., Barrows, F. 2017. Wet processing barley grains into concentrates with protein, beta-glucan, and starch. Cereal Chemistry. 94(2):161-169.
Interpretive Summary: Barley ranks the fourth in world cereal production after corn, rice, and wheat. Worldwide, a significant amount of barley is consumed as livestock feed, a low amount for brewing, and a further lower amount directly as human food. On dry matter basis, barley contains 50–65% starch, 10-16% protein, and 13-22% other carbohydrates. Furthermore, barley is among the very few grains that contain high amounts of the water soluble fiber beta-D-glucan (BG), with a content ranging from 3 to 6%. Clinical studies have shown that BG reduces both serum cholesterol levels and post-prandial blood glucose response. There is a growing interest in incorporating barley into the human diet, since it is naturally healthy, readily available and relatively inexpensive. Many publications have described both wet and dry methods to process barley into fractions enriched with protein, BG, and/or starch, a key strategy to increase value-added utilization of barley. Compared with wet methods, dry fractionation is less expensive, but has low enrichment levels. Therefore, wet extraction is a preferable method. Among all the reported studies on wet fractionation of barley, however, almost all dealt with enrichment of one or two nutrients and neglected other possibly valuable coproducts. Processing parameters investigated and conditions optimized in the previous studies were therefore based on concentration and recovery of only one or two key nutrients. To increase production profitability, a method that can recover all the major nutrients from barley is needed. In a previous study, a wet method for processing oats into fractions enriched with each of key nutrients was developed. In the present study, we further improved the wet method and adopted it for barley processing and optimization.
Technical Abstract: An improved wet method was developed to process barley into fractions concentrated in protein, (1-3)(1-4)-b-D-glucan (BG), starch, or other carbohydrates (CHO). Alkaline concentration, solvent to barley flour ratio (SFR), and extraction temperature were evaluated for their effects on concentration and recovery of protein, BG, starch, oil, ash, and other CHO in each fraction type. Results show that the three parameters and their interactions all had significant effects, resulting in varying nutrient concentrations and recovery rates in each type of fractions. For protein fractions, protein content varied from 37.7 to 75.2%, protein recovery from 8.5 to 75.7%, and increasing alkaline concentration and SFR improved nutrient recovery. For BG fractions, BG content ranged from 21.5 to 87.0%, BG recovery from 28.6 to 78.0%, and increasing alkaline concentration decreased BG content but increased its recovery significantly. For starch fractions, starch content varied from 76.9 to 93.9%, starch recovery from 33.6 to 63.9%, and all parameters had little effect on the nutrient concentrations, but alkaline concentration and SFR improved recovery of starch, other CHO, and mass. Overall, the improved wet method was effective in concentrating the major nutrients from barley into their respective fractions, but process optimization through manipulating the three parameters is necessary to achieve a maximum concentration or recovery rate of a nutrient of interest in a specific fraction.