Study Of Adding Sodium Formate And Calcium Propionate On The Preservation Of Wet Brewer’s Grains

Wet brewer’s grains are by-products in the process of beer brewing,with huge yield and rich nutrients,which have high feeding value in animal production.However,the higher water content of wet brewer’s grains leads to its strong seasonality.Therefore,it is very important to find a simple and economical method to prolong the storage time and make full use of it.sodium formate（SF）and calcium propionate（CAP）are commonly used as food preservatives and feed additives with high safety and low cost.Thus,we try to use these two additives to store wet brewer’s grains,and compare their preservation effect.While prolonging the storage time of wet brewer’s grains,the waste of resources and environmental pollution are reduced,and the utilization value of food processing by-products is also improved.The objective of this research is to study the effect of sodium formate and calcium propionate on the preservation and microbial community of wet brewers’grains under short-term storage.Wet brewers’grains used in the present study were obtained from Jinrun Animal Husbandry Company Limited.There were three main contents in this study:Experiment Ⅰ:The study on the conventional chemical compositions of wet brewer’s grainsThe nutritional compositions and the number of microorganisms in fresh wet brewer’s grains were determined by conventional chemical analysis in the laboratory.The results showed that the content of dry matter（DM）and soluble sugar（WSC）were respectively 27.82%and 0.53%of wet brewers’’grains,as the crude protein（CP）and neutral detergent fiber（NDF）contents were 26.95%and 67.94%.The content of acid detergent fiber（ADF）was 20.53%.The raw material contained lactic acid bacteria and yeast,with the concentrations being 10⁴cfu/g FW and 10³cfu/g FW;whereas no mold could be measured in this study.Experiment Ⅱ:Effects of adding SF and CAP additives on preservation,chemical compositionsand rumen degradation parameters of wet brewers’grainsA single-factor experiment design was employed in this study.The wet brewers grains were randomly treated by one of three treatments:（1）the control（without additive;CON）,（2）addition of sodium formate（SF,3g/kg fresh weight）,and（3）addition of calcium propionate（CAP,3g/kg fresh weight）.There were three replicates in each treatment.All the samples were preserved in the vacuum environment for 20 days.At the 20th day,the pH value,volatile fatty acid（VFA）,lactic acid and ammonia nitrogen（NH₃-N）,chemical compositions and rumen degradation parameters of wet brewer’s grains were analyzed.The results showed that the SF group had the lowest pH value,acetic acid and ammonia nitrogen contents（P<0.05）and highest concentration of lactic acid（P<0.05）,whilebutyric acid content was not detected in the samples.the addition of CAP did not affect pH value and lactic acid concentration（P>0.05）,while increased concentrations of propionic acid.Some mold and rotten couldbe observed in the CON,but no change could be seen among three groups.After 20 days,the SF group had the highest contents of DM,WSC and NDF,and DM loss was significantly lower than that in the other two treatment groups（P<0.05）.The contents of the these three nutrients in the CAP group was also significantly higher than that in the CON group（P<0.05）,and the DM loss was not significantly different from that in the CON（P>0.05）.The addition of the two additives did not affect the CP and ADF content of the wet brewers’grains（P>0.05）.Compared with the CON group,two additives elevated rumen effective degradability of DM,NDF（P<0.05）,and the wet brewers’grains with SF addition had higher rumen effective CP degradability than that in the CON group and CAP group（P<0.05）.Experiment Ⅲ:Effects of adding sodium formate and calcium propionate on the microbial community of wet brewers’grainsThe results of Alpha diversity analysis showed that the addition of sodium formate and calcium propionate increased the species richness and community diversity of microbiota in fermented wet brewers’grains（P<0.05）.The results of principal component analysis showed that the SF group and the other two groups had a large difference in bacterial compositions.The analysis of the genus level of the bacterial flora showed that the relative abundance of Lactobacillus in the SF group was significantly higher than that in the other two treatment groups（P<0.05）,while the relative abundance of Clostridium was significantly lower than that in the other two treatment groups（P<0.05）.The results of prediction and analysis of the function of bacteria in fermented wet beer dregs showed that sodium formate significantly decreased the relative abundance of functional groups of amino acid and carbohydrate metabolism（P<0.05）.Spearman correlation analysis showed that the relative abundances of Lactobacillus,Bacillus,Weissiella and Acinetobacter was negatively correlated with pH,acetic acid,butyric acid and ammonia nitrogen contents,and positively correlated with lactic acid content,while Clostridium was changedin the oppositetendence（P<0.05）.All the data showed that both additives could improve the quality of preserved wet brewers’grains to some extent,but with the same addition level,wet brewers’grains treated with SF showed better preservation quality.