Department of Biological Science, Cork Institute of Technology, Bishopstown, Cork, Ireland.
School of Nutrition and Health, University College Cork, Cork, Ireland.
Food Microbiol. 2020 Sep;90:103464. doi: 10.1016/j.fm.2020.103464. Epub 2020 Feb 21.
Achieving a high monosaccharide composition in malt wort is instrumental to achieve successful lactic acid bacteria fermentation of malt based beverages. The conversion of monosaccharides to alternative metabolites such as the sweet polyol, mannitol with heterofermentative strains presents a novel approach for sugar reduction and to compensate for the loss of sweetness. This work outlines the application of an adopted mashing regimen with the addition of exogenous enzymes to produce wort with high fructose content which can be applied to different malted grain types with consistently efficacious monosaccharide production for bacterial fermentation. The so produced worts are then fermented with Leuconostoc citreum TR116 a mannitol hyper-producer. Malted barley, oat and wheat were mashed to stimulate protein degradation and release of free amino acids along with the enzymatic conversion of starch to fermentable sugars. Amyloglucosidase and glucose isomerase treatment converted di- and oligo-saccharides to glucose and provided a moderate fructose concentration in malt worts which was consistent across the three cereals. Fructose was completely depleted during fermentation with Lc. Citreum TR116 and converted to mannitol with high efficiency (>90%) while overall sugar reduction was >25% in all malt worts. Differences in amino acid composition of malt worts did not significantly affect growth of Lc. Citreum TR116 but did affect the formation of the aroma compounds diacetyl and isoamyl alcohol. Organic acid production and acidification of wort was similar across cereal substrates and acetic acid formation was linked to yield of mannitol. The results suggest that differences in amino acid and fructose content of malt worts considerably change metabolite formation during fermentation with Lc. Citreum TR116, a mannitol hyper-producer. This work gives new insight into the development of consumer acceptable malt based beverages which will provide further options for the health conscious and diabetic consumer, an important step in the age of sugar overconsumption.
实现麦芽汁中单糖组成的高含量对于成功进行基于麦芽的饮料中乳酸菌发酵至关重要。将单糖转化为替代代谢物，如具有异型发酵能力的菌株的甜味多元醇甘露醇，为减少糖含量和补偿甜度损失提供了一种新方法。本工作概述了采用外加酶的糖化方案的应用，以生产高果糖含量的麦汁，可应用于不同类型的麦芽谷物，始终有效地生产用于细菌发酵的单糖。然后，用甘露醇高产菌乳明串珠菌 TR116 发酵如此生产的麦汁。将大麦、燕麦和小麦进行糖化，以刺激蛋白质降解和游离氨基酸的释放，同时酶促转化淀粉为可发酵糖。糖化酶和葡萄糖异构酶处理将二糖和寡糖转化为葡萄糖，并在三种谷物的麦芽汁中提供了中等浓度的果糖。在与乳明串珠菌 TR116 的发酵过程中，果糖完全耗尽，并高效（>90%）转化为甘露醇，而所有麦芽汁的总糖减少量均超过 25%。麦芽汁中氨基酸组成的差异不会显著影响乳明串珠菌 TR116 的生长，但会影响双乙酰和异戊醇的香气化合物的形成。在不同的谷物基质中，有机酸的产生和麦汁的酸化相似，并且乙酸的形成与甘露醇的产率有关。结果表明，氨基酸和果糖含量的差异会显著改变与甘露醇高产菌乳明串珠菌 TR116 发酵过程中的代谢产物形成。这一工作为开发消费者可接受的基于麦芽的饮料提供了新的见解，为注重健康和糖尿病患者提供了更多选择，这是在糖过度消费时代的重要一步。
