| Chicken seasoning(CS)is gradually gaining popularity among consumers because of its unique advantages.The industry standard "SB/T 10371-2003" stipulates that the flavor of CS should be mellow chicken flavor with no undesirable flavor,but the manufacturers have found CS can deteriorate during the shelf life(usually marked as 20 months)and produce an unpleasant rancid flavor,which may be caused by fat oxidation.However,since the fat content in CS is extremely low(<1%),there are no studies on CS fat and no suitable method to assess the oxidative stability of CS,so the oxidative stability evaluation method has become a problem that restricts the development of manufacturers.Therefore,this paper analyzes the similarities and differences in fat composition and quality of several commercially available fresh CS;and on this basis,analyze the differences in fat composition and quality between fresh and deteriorated CS to derive sensitive indicators that can quantitatively evaluate the deterioration of CS,which is used to establishment the method of evaluating the oxidative stability of CS based on changes in fat quality.Firstly,seven commercially available brands CS(all about 4 months old)were used as raw materials to analyze the similarities and differences in their fat composition and quality.The results showed that the fat content of commercially available CS was very low(0.17%～0.68%),and the fat composition of CS was mainly glycerol triglycerides(>95%),followed by glycerol diesters,glycerol monoesters and free fatty acids;the main fatty acids of CS were oleic acid,palmitic acid and linoleic acid;the peroxide values of CS differed,with the highest peroxide value being 0.053 mmol/kg;the differences in flavor and volatile compounds can be attributed to the differences in flavoring techniques and production formulations of manufacturers,with fatty flavor mainly coming from hexanal,heptanal,(E)-2-octenal,octanal,nonanal produced by moderate oxidation of fat.Next,fresh and deteriorated CS of the same brand were used as raw materials to compare the differences in fat composition and quality.The results showed that as CS deteriorated,CS fat underwent obvious hydrolysis and oxidation reactions,with the hydrolysis reaction being primarily manifested in the decrease of glycerol triglyceride content and the increase of free fatty acid content;the oxidation reaction being primarily manifested in the decrease of CS fat linoleic acid content,the increase of CS peroxide value,and the secondary oxidation products of fat hexanal,heptanal,octanal,(E)-2-octenal,nonanal,decanal and(E,E)-2,4-nonadienal.Correlation analysis of the sensory properties of CS with the volatile compound content revealed that fat oxidation(primarily the oxidation of linoleic and oleic acids)was the root cause of rancid flavor,which was composed of secondary oxidation products of fat,with hexanal being the most important component,and the threshold value of rancid flavor in CS is when the hexanal content is 80 μg/kg.Four indicators were developed to assess the degree of deterioration(fat oxidation)of CS: hexanal content,peroxide value,linoleic acid content,and free fatty acid or glycerol triglyceride content.Finally,the effect of temperature,relative humidity and UV light on accelerating the fat oxidation of CS was investigated using the same brand of fresh CS as raw material to establish a method for evaluating the oxidative stability of CS on this basis.The results showed that the oxidation rate of CS was slow during storage at 50-80℃,the color of CS changed from light yellow to brown,and the content of pyrazine of CS increased rapidly,which presumably that the fat oxidation of CS was inhibited by the Maillard reaction under high temperature;then the temperature was lowered and the humidity was increased for the storage of CS(30～50℃/80RH%),and the oxidation effect of CS was not obvious because the aluminum foil package was well sealed.Then,the oxidation of CS was accelerated by365 nm UV light irradiation,and it was found that the oxidation speed of CS was extremely fast,and the threshold value of hexanal was exceeded 80 μg/kg after 48 h of light irradiation,which made it difficult to effectively distinguish the difference of oxidation stability of CS.Finally,the automatic oxidation reaction of CS was accelerated with the increase of storage temperature and the extension of light time under this condition,The final method was determined to evaluate the oxidative stability of CS by monitoring the time of hexanal reaching 80 μg/kg with pretreatment of 18 h UV light and storage at 50℃.The method was used to accelerate four CS with different production dates to verify the effectiveness of the method.There was a good linear relationship between the hexanal content and storage time.The time of reaching 80 μg/kg were: 0.22 days,1.21 days,3.34 days and 6.32 days. |
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