| Among all the cereals, oat kernels have much higher lipase and lipoxidase activities, which caused oat foods vulnerable to oxidation and spoilage in processing and storage. Thus the enzymatic deactivation treatments in oat processing are necessary to provide oat products with required quality and safety. Normal pressure steaming (NPS), and hot air roasting (HAR) are traditionally used to deactivate the activities of lipid enzymes in the oat industry in China, while infrared roasting (IR), a novel enzyme deactivation method, is believed to better meet the requirement of the industrialization of the oat food production in the country. In this study, oat kernels were subjected to one of the three enzyme deactivation treatments before ground. In order to reveal the effect of these processing on some functional properties, quantity of some nutritional components, and in vitro starch and protein digestibility were assessed. We also employed Sprague-Dawleys rats to study the effects of different lipid enzyme deactivation treated oats on the hyperglycemia, hypolipemic and insulin sensitivity through the measurement of various biochemical indicators with comparison to control group. Also the intestinal effects, including energy charge, intestinal flora, short chain fatty acid and pH in colon of rats, were tested. And HE pictures were used to observe complications of intestinal villi, tunica muscularis of small intestine (duodenum, jejunum and ileum).The main results are as follows:(1) It indicated that compared with the control group, infrared roasting had no significant effect on contents ofβ-glucan, protein and fat, and can maintain the nutritional components of oat whole flour. The infrared roasting lowered the initial gelatinization temperature and increased peak viscosity and cool viscosity of oat whole flour to improve quality of oat products.Results of the in vitro starch digestibility indicated that hot air roasting, normal pressure steaming and infrared roasting increased the content of resistant starch in oat whole flour, while had no significant effect on the content of slowly digestible starch. Infrared roasting showed highest protein digestibility of 70.05% according to the in vitro protein experiment. While hot air roasting and normal pressure steaming had different effect on the nutritional components of oat whole flour, the infrared roasting had no significant effect on that.(2) Compared with the control group, all the treatments of oat-based diets resulted in significantly higher water intake, diet intake, body weight gain, fecal wet weight and fecal dry weight(P<0.05). There were no significant differences (P>0.05) in the levels of diet intake, body weight gain and fecal discharge among the four oat-based diets groups.The levels of serum TG and LDL-C in each oat-based diet group was significantly lower (P<0.05) than in the control group, while there were no significant differences in the levels of TG and LDL-C among the four oat-based diet groups (P>0.05). The TC levels of rats taking the normal oat diet or the IR treated oat diet were significantly lower (P<0.05) than those of rats taking the control diet. Each oat diet group showed lower HDL-C level than the control group, however, there were no significant differences in HDL-C levels among all the five groups (P>0.05).The results of oral glucose tolerance test (OGTT), insulin sensitivity index (ISI) and the postprandial glucose response test (PGRT) showed that rats fed the oat-based diets blunted the postprandial glucose response, increased glucose tolerance and increase insulin sensivivity in normal SD rats without significant differences.(3) Oat-based diets increased ATP and Energy charge (EC) of jejunum and ileum of rats compared with the control group (P<0.05) to improve the contract ability of jejunum and ileum of rats. Significantly increases of the numbers of Bifidobacteria, Lactic acid bacteria and decreases of E. coli and Enterococcus strains in the content of colon(P<0.05), cecum and fresh faeces of rats fed the oat diets were found compared with that of the control groups. In the colon, the oat-based diets led to higher productions of total short chain fatty, and acetic acid and butyrate compared with the control group (P<0.05). But there were no significant difference among the four oat-based diet groups. The pH of the colon and cecum content of rats fed the oat-based groups was lower in experimental groups, especially in the HAR-treated groups.(4) Futhermore, the organ pathological condition of rats was investigated with the employment of HE dyeing technology. Compared with the control group, rats fed the oat-based diets showed larger number of goblet cells of the small intestine epithelium, and more intestinal gland of the small intestine. Rats fed the oat-based diets had shorter villus heights and villus perimeters of duodenum (P <0.05) compared with the control group, but there were no significant differents on the villus heights and villus perimeters of jejunum and ileum among the experimental groups. Compared with the control group, rats fed oat-based diets increased the crypt height and thickness of mucles without significant differences.The results suggested that the IR-treated, HAR-treated or NPS-treated oat diets had the same beneficial functions as normal oat diets. The oat diets, either enzyme-deactivated or not, could help to improve blood lipid profiles, regulate intestinal flora in normal SD rats. The infrared roasting had no significant effects on nutritional components of oat whole flour and favorable for protein digestibly. |
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