Effects of Different Extrusion Puffing Processes on Comprehensive Utilization of Soybean Meal Protein in Vitro
This study was conducted to investigate the effects of different extrusion puffing processes on the ru-men 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 puff-ing(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),soy-bean 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 pro-tein composition,were determined,and the effects of extrusion puffing processes on the degree of Maillard re-action 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(△E)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* and △E 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 signif-icantly 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 digesti-bility 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-degrad-able 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(NH3-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 con-tent(P＞0.05),but changed the volatile fatty acid composition in rumen fluid,in which the contents of isobu-tyric 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]
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