Impact Of Heat-Related Processing Treatment And Strains On The Physicochemical,Nutritional Traits And Molecular Structure Of Newly Developed Sorghum Seeds

Recently,Chapingo Autonomous University in Mexico successfully cultivated three new strains of warm-season sorghum(Dkalb DKS43,Pioneer 82G93 and Pioneer 8133).Each sample was either kept as raw(control)or treated by dry heat-related processing using the Lindberg/Blue M?,Moldatherm? for 80 min at 121 °C.This thesis aimed to systematically investigate the heat-induced changes of nutrient compositions and the characteristics of degradation and digestion of warm-season sorghum grains,also the differences of nutrient compositions and the characteristics of degradation and digestion among these three strains of warm-season sorghum.To achieve the objectives,we used five evaluation methods commonly used in ruminant nutrition,including conventional chemical analysis,Cornell Net carbohydrate And Protein System(CNCPS v6.5)model evalution,estimation of energy and truly digestible nutrition(NRC 2001 and NRC,1996),in situ rumen degradation,in vitro intestinal digestion.Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy(ATR-FTIR)was used to detect the molecular structure of sorghum grains directly.It revealed the dry heat-induced effect of sorghum grain internal structure via quantifying the protein related molecular structures and the internal structural differences among Dkalb DKS43,Pioneer 82G93 and Pioneer 8133 sorghum grains.The correlation analysis between protein related molecular structures and the nutrient composition as well as nutrient digestion characteristics of sorghum grain were conducted.Regression models were utilized to predict digestion and utilization of nutrients of sorghum grains using protein molecular structure characteristics.The research results showed that:1.The fiber contents(NDF,ADF and cellulose)of warm-season sorghum grains were significantly increased by heat treatment,further caused t RDC increased.Although heat treatment had no effects on protein fractions,protein supply,protein degradation,and digestion,it significantly changed the protein molecular structure. Heat treatment did not affect td NDF,td CP,td FA and td NFC,but increased DE1×,ME,NEm and NEg.In conclusion,dry heating altered chemical and nutrient profiles and nutrient supply of three strains of sorghum grains without negatively impact the degradation and digestion of the nutrients.The molecular spectral profiles could be used as a potential predictor for the utilization and digestion of the warm-season sorghum grain.2.Among the three strains of warm-season sorghum,Pioneer 82G93 and Pioneer 8133 were different in chemical nutrient composition,nutrition supply and protein related molecular structure.CP and carbohydrate(CHO,NFC,NDF,ADF,cellulose and hemicellulosic)contents were different among these sorghum grains.The contents of ADF and cellulose of Dkalb DKS43 were higher than the other two genotypes of sorghum grains.The CP contents of Dkalb DKS43 and Pioneer 82G93 were similar and both of them are higher than Pionner 8133.However,Pioneer 82G93 and Pioneer 8133 had no differences in protein degradation and digestion characteristics,while Dkalb DKS43 showed significant differences compared with the other two.The contents of td NDF,td NFC and td CP in these three sorghum grains were different.In addition,there was no differences in the TDN1×,DE1×,DEp3×,MEp3×,NEL3×,ME,NEm and NEg among these three sorghum grains.Above all,Dkalb DKS43 was more different compared with Pioneer 82G93 and Pioneer 8133,especially in the digestion behavior of crude protein.3.Three strains of warm-season sorghum grains(Dekalb DKS43,Pioneer 82G93 and Pioneer 8133)were used as models for ATR-FTIR molecular spectral analysis.The results revealed that there was a close correlation between the protein structural characteristics and the chemical components,protein fractions estimated by CNCPS v6.5,truly digestible nutrient,rumen degradation and intestinal digestion of sorghum grains.Amide I and amide II area and peak height,and α-helix and β-sheet peak height were positively correlated with CP(r ≥ 0.72),ADICP(r ≥ 0.58),PB1(r ≥ 0.50),t RUP(r ≥ 0.85),t RDP(r ≥ 0.56)and td CP(r ≥ 0.69).The area ratio of amide I and II was negatively correlated with CP(r =-0.73),ADICP(r =-0.65),t RDP(r =-0.66),t RUP(r =-0.77)and td CP(r =-0.72).The peak height ratio of α-helix and β-sheet was negatively correlated with ADF(r = 0.71),NDF(r = 0.59),SCP(r = 0.86),t RDP(r = 0.63),td NDF(r = 0.60),RDDM(r = 0.77),RDCP(r = 0.71)and d RUP(r = 0.95),it was positively correlated with PB2(r = 0.93).The correlation between protein molecular structure characteristics and DE1×、DEp3×、MEp3×、NELp3×、ME、NEm and NEg were not significant(P > 0.05).Protein related molecular structures can be used as potential indicators to predict the utilization and digestion of newly developed warm-season sorghum grains.