Research And Application Of Preparing Dog Food Attractant By Waste Beer Yeast

Dog food attractant is a special additive added into dog food, in order to improve the palatability, digestion and absorption of dog food as well as increasing appetite. So far, many researchers merely focused on sweeteners, amino acids and fat, rather than the key flavor compounds, to increase palatability of dog food. In the current study, the key flavor compounds were determined by establishing the relationship between palatability values of products and volatile compounds. Furthermore, with the amount of the key flavor compounds as the reference, the technological conditions to process dog food attractant prepared with beer yeast residual were optimized and its efficacy was investigated. The main contents and results for this study are as follows:Seven different levels of dry dog foods and 4 different flavor dog food attractants were selected from the market and they were separately ranked in terms of palatability. In order to find out the key flavor compounds that could increase the palatability of dog food,the volatile compounds of dog foods and dog food attractants were detected with SPME-GC-MS. It showed that 56 aromatic compounds were tentatively identified in the 7 dry dog foods while 78 aromatic compounds in the 4 dry dog food attractants. With the analysis of Partial Least Squares Regression(PLSR) to build up the relationship between the volatile compounds and palatability, the results suggested that the key flavor compounds contributing to the palatability were mainly aldehydes, heterocycle compounds and etc. It was worth noting that some volatile compounds were present in both results of the dog foods and attractants, such as octanal, benzaldehyde, ethyl vanillin, vanillin, anisole, ethyl maltol, furfural and Tert-butylhydroquinone. Therefore, nonanal(63.80 μg/g), benzaldehyde(29.13 μg/g), furfural(5.20 μg/g), vanillin(50.56 μg/g), ethyl maltol(44.05 μg/g) and 2,5-dimethyl pyrazine(4.00 μg/g) were chosen for adding-back validation experiments, and the results showed that IR of vanillin and 2,5-dimethyl pyrazine were up to 75%, over 65% for benzaldehyde, ethyl maltol and furfural, and about 60% for vanillin and 2,5-dimethyl pyrazine.The primary key compounds are aldehydes and heterocycle compounds, which could be prepared by Maillard reaction. Firstly, with the beer yeast residual as the source of amino acids and the degree of hydrolysis as the index, the optimization condition of autolysis was 45 oC, p H 6.5, three times water, 0.3% flavor enzyme(2.2×104 U), 20 h. The amount of free amino acids could reach up to 40% under this condition, and HD of Cys and Met were more than 90%, which would be able to be as reactant of Maillard reaction. Then, the reactant(xylose), important flavor precursor(thiamine), flavor enhancer(vitamine C), and L-Cysteine monohydrochloride because of inadequate sulfur-containing amino were added back to produce Maillard reaction. Then, with the amount of key flavor compounds as index to determine the raw materials of Maillard reaction: 3.0% xylose, 0.5%L- cysteine hydrochloride, 1.5% thiamine, 0.5% vitamin C. Also, the condition of maillard reaction: 120 °C,p H 8.0, 1 h. The last step was to add gum arabic powder and maltodextrin in Maillard reaction liquid and spray drying to prepare the lab version of dog food attractant.The efficacy of the lab version of dog food attractant was investigated by preference tests, and the results showed it was at intermediate level. The palatability of the lab version of dog food attractant could be improved by adding ethyl maltol and 2,5-dimethyl pyrazine. When the modified attractants were spread on six types of market dog foods, the results showed that their palatabilities were correspondingly improved.Also, the degree of oil oxidation and microbial counts are the important indices for judging the storage stability of dog food and p H has a great influence on it. The peroxide value(POV) and aerobic plate count were applied to determine the effect of the p H of attractant(2~6) on dog food. The results illustrated that the POV of samples spread with attractants were reduced by 21%~33% and the attractants had some antioxidation effects showed from DPPH data. The highest DPPH free radical scavenging activity was around 90%. Besides, the DPPH free radical scavenging activity would increase as increasing p H and the reducing power was the highest when p H was 4. Since the attractant could inhibit the growth of microorganisms, the total aerobic plate count was reduced from 103 to 102 after spreading attractants. The Bacteriostatic ring size of attractants with different p H showed that the antibacterial activity on E. coli increased and S. aureu decreased as increasing p H. Nevertheless, the palatability tests showed that within the range of p H 4 to 6, p H had no significant effects on the palatability of dog food. So the p H of attractant by-hand is 4.