Effect Of Brine Aging And Different Processing Techniques On Flavor Compounds Of Water Boild Salted Duck

Water boiled salted duck was one of the few low temperature cooked meat products in traditional Chinese featured meat products. It was famous for its delicate processing, savory, and tender flavor. Brining was one of the most important processing which made a great contribution to the flavor of ducks. In China, the brine used in brining was classified by its using time and frequency. The fresh brine was made up of many spices in particular proportion, so it had a palatable taste. With brining many materials and adding enough spices, more and more soluble materials dissolved in brine, the brine were more and more delicious. When the brine was used for many years, it became aged brine. The longer time the brine was used, the stronger flavor it was and its contribution to duck meat was better too. However, to our knowledge, little study has so far been reported regarding brine of water boiled salted duck. Salting, brining, drying and boiling were the main four processes, which made a great contributiong to the flavor of ducks. At present, the different processing method after brining were the main differences in techniques of water boiled salted duck. Drying with low temperature, cooling and boiling directly were the main three methods after brining.The aim of this research is to study the differences of two kinds of brines and study the effects of flavor in water boiled duck with the two kinds of brines and three different processing methods, so as to provide a theory basis for studying and accommodating the flavor, improving the processing technology, optimizing the parameters of water boiled salted duck. The contents and results are as follows:1Study on basic compounds and flavor compounds of brineThe basic compounds and flavor compounds in fresh brine and aged brine were studied in this part. The results showed that the basic compounds such as protein and fat of aged brine were more than these of fresh brine. The total free amino acids of aged brine was17.99mg/100g, significantly greater than fresh brine which was only5.07mg/100g (P<0.05). The flavor amino acids(including aspartic acid, glutamic acids), because of its relatively low threshaged, made a great contribution to the taste of brine and product. Sweet and bitter components were the main free amino acids of fresh brine and aged brine. Isoleucine, phenylalanine, arginine and nucleotides were mainly from the soluble ingredients of duck meats. When for the volatile falvor vompounds,79kinds of compounds were identified in these two kinds of brine including hydrocarbons(20kinds), aromatic hydrocarbons(8kinds), ketones(6kinds), alcohols(13kinds), aldehydes(12kinds), esters(3kinds), furans(1kinds), heterocyclic compounds (4kinds) and N-containing compounds(2kinds). Aldehydes, alcohols and hydrocarbons were the main compounds in fresh brine, while aldehydes, aromatic hydrocarbons and heterocyclic compounds were the main compounds in aged brine.The ketones, aldehydes, furans, aromatic hydrocarbons, heterocyclic and N-containing compounds in aged brine were more than in fresh brine. The aldehydes, such as cinnamaldehyde, benzaldehyde, hexanal,3-methy butanal and furfural as well as the heterocyclic and N-containing compounds which had a lower threshole value, maybe play an important role to the flavor of brine and duck meat.2Effect of brine aging on flavor compounds of water boiled salted duckRaw ducks (Cherry valley duck) were processed following the traditional methods, except brining with the two kinds of brine.The basic compounds, taste compounds and volatile flavor compounds in duck meats were analyzed. The results showed that basic compounds of water boiled salted duck meat were not affected significantly by the brine but brining could increase the content of free amino acids in duck meat. The vast majority of free amino acids in water boiled salted duck meat of aged brine were more than that of fresh brine. Glutamic acid, alanine, lysine, leucine and arginine were the most abundant free amino acids in water boiled salted duck meat. Synergistic effect of free amino acids in brine and duck meat increased the content of them in duck meat, which contributed to the taste of water boiled salted duck meat. A number of nucleotides and their degradation products in duck meat of aged brine were more than that of fresh brine, which could be one of the reasons contributing to the delicious taste of duck meat. Aldehyde, alcohols, ketones were the main compounds in duck meat of the two kinds of brine.Water boiled salted duck meat of aged brine had more hydrocarbons, aromatic hydrocarbons, ketones, aldehydes, furans, N-and S-containing compounds than duck meat of fresh brine.Most of these compounds were degradation products of fat oxidation, may be the important flavor source of duck meat. Through the sensory evaluation and comprehensive analysis of some compounds, water boiled salted duck meat of aged brine had better colour, juiciness, aroma and taste than duck meat of fresh brine, also had a better comprehensive impression.3Effect of different processing techniques on flavor compounds of water boiled salted duckRaw ducks (Cherry valley duck) were processed following three different methods. The differences of the methods were the process after brining. Drying with low temperature, cooling and boiling directly were the main three methods after brining. The results showed that cooling after brining could significantly increase the content of fat of duck meat (P<0.05), drying and cooling could increase the pH value and salt content. After boiling, duck meat of drying group had the highest fat and salt content and the pH value. Drying could increase the content of MSG-like component, sweet component and nucleotides of duck meats which was good for its taste, while cooling could increase the content of bitter component of duck meat and decreased sweet component which was bad for its taste.Drying could increase the content of hydrocarbons, alcohols, acids, aldehydes, esters, furans and S-containing compounds of duck meat, especially the content of propanal, pentanal, hexanal, heptanal, octanal, nonanal,(E,E)-2,4-heptadiene, benzaldehyde. N-containing compounds in water boiled salted duck meat of drying group were more than the other groups (P<0.05). These compounds could play important roles for the specific flavor of water boiled salted duck.Cooling could increase the content of hydrocarbons, aldehydes, acids, S-containing compounds and heterocyclic compounds of ducks meats. Content of hydrocarbons, ketones, esters were the highest in water boiled salted duck meats of cooling group.Through the sensory evaluation and comprehensive analysis of some compounds, water boiled salted duck meat of drying group was superior to the other two groups in juiciness, aroma and taste, and had the best impression.