体外培养条件下不同挤压膨化工艺对豆粕蛋白质综合利用效果的影响

Corresponding author,associate professor,E-mail:suhuawei@cau.edu.cn Effects of Different Extrusion Puffing Processes on Comprehensive Utilization of Soybean Meal Protein in Vitro

本试验旨在通过体外三步法探究不同挤压膨化工艺对豆粕瘤胃发酵和小肠消化的影响。采用单因素随机试验设计,分别制备豆粕[对照组(CON组)]、挤压膨化豆粕(E组)、膨化前添加3%大豆毛油豆粕(AO组)、膨化后添加3%大豆毛油豆粕(CO组)、膨化前后均添加3%大豆毛油豆粕(AO-CO组)、膨化前添加4%葡萄糖豆粕(GE组)、膨化前添加4%葡萄糖和3%大豆毛油豆粕(GAO组)、膨化前添加4%葡萄糖和膨化后添加3%大豆毛油豆粕(GCO组)和膨化前加4%葡萄糖和膨化前后均添加3%大豆毛油豆粕(GAO-CO组),共9组样品。通过测定挤出物性质(色差、褐变程度以及纤维和蛋白质组成),探究挤压膨化工艺对豆粕蛋白质美拉德反应程度的影响。进一步选用3头体重600 kg装有永久性瘤胃瘘管的安格斯阉牛,采用体外三步法(瘤胃液-胃蛋白酶-胰蛋白酶)测定挤压膨化后豆粕瘤胃降解特性和瘤胃不可降解蛋白质(RUP)的体外小肠消化率。结果表明:1)挤压膨化后的色差结果显示,各试验组红度(a*)、黄度(b*)、色差(ΔE)和420 nm吸光度(OD)值相较于CON组显著提高(P<0.05),亮度(L*)值(AO组除外)显著降低(P<0.05)。GAO组294 nm OD值显著低于只添加1种反应物的AO组和GE组(P<0.05),a*和ΔE值显著低于GE组(P<0.05)。除GCO组外,GE组中性洗涤纤维(NDF)和中性洗涤不溶粗蛋白质(NDICP)含量相较于CON组和其他试验组显著提高(P<0.05)。2)与CON组相比,各试验组干物质(DM)和粗蛋白质(CP)的过瘤胃率、体外小肠消化率、体外全消化道消化率以及RUP和小肠可消化粗蛋白质(IDCP)含量显著提高(P<0.05)。GE组DM和CP的过瘤胃率以及RUP和IDCP含量(E组除外)显著高于其他试验组(P<0.05)。3)体外发酵16 h后,各试验组瘤胃液pH和氨态氮(NH3-N)含量相较于CON组显著降低(P<0.05);挤压膨化未对总挥发性脂肪酸(TVFA)含量产生显著影响(P>0.05),但改变了瘤胃液的挥发性脂肪酸组成,其中各试验组瘤胃液中异丁酸、异戊酸和总支链挥发性脂肪酸(TBCVFA)含量显著低于CON组(P<0.05)。综上所述,添加葡萄糖能够提高挤压膨化过程中美拉德反应的程度,促进豆粕优质蛋白质的过瘤胃而转向小肠消化吸收,但添加富含不饱和脂肪酸的大豆毛油会抑制挤压膨化过程中的美拉德反应。因此,推荐挤压膨化过程中添加葡萄糖来提高膨化效果,且不建议添加富含不饱和脂肪酸的大豆毛油。

This study was conducted to investigate the effects of different extrusion puffing processes on the rumen fermentation and small intestinal digestion of soybean meal through a three-step in vitro method.A single-factor randomized trial design was used to prepare the nine samples,which were soybean meal(CON group),extrusion puffing soybean meal(E group),soybean meal adding 3%soybean crude oil before extrusion puffing(AO group),soybean meal adding 3%soybean crude oil after extrusion puffing(CO group),soybean meal adding 3%soybean crude oil at the same time before and after extrusion puffing(AO-CO group),soybean meal adding 4%glucose before extrusion puffing(GE group),soybean meal adding 4%glucose and 3%soybean crude oil before extrusion puffing(GAO group),soybean meal adding 4%glucose before extrusion puffing and 3%soybean crude oil after extrusion puffing(GCO group),and soybean meal adding 4%glucose before extrusion puffing and 3%soybean crude oil at the same time before and after extrusion puffing(GAO-CO group).The properties of the extrudate,such as color difference,degree of browning,and fiber and protein composition,were determined,and the effects of extrusion puffing processes on the degree of Maillard reaction of soybean meal protein were investigated.Then 3 Angus steers with permanent rumen fistulas weighing about 600 kg were selected to estimate the rumen degradation characteristics of soybean meal after extrusion puffing and the small intestinal digestibility of its rumen undegradable protein(RUP)was determined by a three-step in vitro method,which was metabolized by rumen fluid,then pepsin and finally trypsin.The results showed as follows:1)the results of color difference after extrusion puffing showed that the values of redness(a),yellowness(b),color difference(ΔE)and absorbance(OD)at 420 nm in experimental groups were significantly increased compared with CON group(P<0.05),and the brightness(L)value(except for AO group)was significantly decreased(P<0.05).The OD value at 294 nm in GAO group was significantly lower than that in AO and GE groups which were with only one reactant added(P<0.05),and the values of a andΔE were significantly lower than those in GE group(P<0.05).Except for GCO group,the contents of neutral detergent fiber(NDF)and neutral detergent insoluble crude protein(NDICP)in GE group were significantly increased compared with CON group and the other experimental groups(P<0.05).2)Compared with CON group,the rumen non-degradable rates,small intestinal digestibility in vitro,total digestive tract digestibility in vitro of dry matter(DM)and crude protein(CP)and contents of RUP and small intestine digestible crude protein(IDCP)in experimental groups were significantly increased(P<0.05).The rumen non-degradable rates of DM and CP and contents of RUP and IDCP(except for E group)in GE group were significantly higher than those in the other experimental groups(P<0.05).3)After 16 h in vitro fermentation,the pH and ammonia nitrogen(NH 3-N)content in rumen fluid in experimental groups were significantly lower than those in CON group(P<0.05).Extrusion puffing did not have a significant effect on the total volatile fatty acid content(P>0.05),but changed the volatile fatty acid composition in rumen fluid,in which the contents of isobutyric acid,isovaleric acid and total branched-chain volatile fatty acid in rumen fluid in experimental groups were significantly decreased compared with CON group(P<0.05).In conclusion,the addition of glucose can improve the degree of Maillard reaction during extrusion puffing and promote the digestion and absorption of high-quality protein from soybean meal through rumen to small intestine,but the addition of soybean oil rich in unsaturated fatty acids can inhibit the Maillard reaction during extrusion puffing.Therefore,it is recommended to add glucose during extrusion puffing,while not recommended to add oils rich in unsaturated fatty acids.[Chinese Journal of Animal Nutrition,2024,36(6):4036-4049]