Rahman Md Jiaur, Malunga Lovemore Nkhata, Eskin Michael, Eck Peter, Thandapilly Sijo Joseph, Thiyam-Hollander Usha
Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, Canada.
Richardson Center for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, MB, Canada.
Front Nutr. 2021 Apr 13;8:634519. doi: 10.3389/fnut.2021.634519. eCollection 2021.
Thermal processing not only disrupts cell membranes and cell walls, but also cleaves covalent bonds releasing low molecular phenolic. This study examined the impact of various heat treatments (100, 140, and 160°C) on the composition of phenolic acids and antioxidant activities in extracts obtained from defatted brewers spent grain (BSG) meal. Heating BSG at 160°C resulted in a 2-fold increase in total phenolic content [TPC, 172.98 ± 7.3 mg Gallic acid equivalent (GAE)/100 g defatted meal] and total flavonoid content [TFC, 16.15 ± 2.22 catechin equivalents (CE)/100 g defatted meal] compared to the untreated BSG extracts. The antioxidant activities of treated BSG extracts, determined by radical scavenging and ferric reducing antioxidant power (FRAP) were significantly ( < 0.5) higher than the corresponding untreated BSG extracts. Eleven phenolic acids were identified and quantified in BSG extracts by Ultra Performance Liquid Chromatography with Photodiode Array (UPLC-PDA). The amounts varied significantly ( < 0.05) depending on the degree of toasting BSG was subjected to. Chlorogenic acid, an ester of caffeic and quinic acid was the predominant phenolic acid present in all fractions. Significant ( < 0.05) increases in TPC, TFC, individual phenolic acids and antioxidant activity were observed in BSG extracts exposed to increasing oven temperatures. These results confirm the ability of heat processing to release bioactive phenolic from their bound forms thereby enhancing the phenolic acids and the digestibility of BSG meal in the intestinal tract.
热加工不仅会破坏细胞膜和细胞壁，还会裂解共价键，释放出低分子酚类物质。本研究考察了不同热处理温度（100、140和160°C）对从脱脂啤酒糟粕（BSG）中提取的酚酸组成和抗氧化活性的影响。与未处理的BSG提取物相比，在160°C下加热BSG可使总酚含量（TPC，172.98±7.3毫克没食子酸当量（GAE）/100克脱脂粕）和总黄酮含量（TFC，16.15±2.22儿茶素当量（CE）/100克脱脂粕）增加两倍。通过自由基清除和铁还原抗氧化能力（FRAP）测定，处理后的BSG提取物的抗氧化活性显著（<0.5）高于相应的未处理BSG提取物。采用超高效液相色谱-光电二极管阵列（UPLC-PDA）对BSG提取物中的11种酚酸进行了鉴定和定量。其含量因BSG的烘焙程度不同而有显著差异（<0.05）。绿原酸，一种咖啡酸和奎尼酸的酯，是所有组分中主要的酚酸。在暴露于不断升高的烘箱温度下的BSG提取物中，观察到TPC、TFC、单个酚酸和抗氧化活性显著（<0.05）增加。这些结果证实了热加工能够从其结合形式中释放生物活性酚类物质，从而提高BSG粕中酚酸的含量以及在肠道中的消化率。
