Study On Process Of Parain-Tenderizing, Curing, Air-drying And Ripening For Spent Layers And Its Quality

There are nearly two billion layers to fall into disusing every year in China.The spent layers' meat is hard because of much collagen in muscle.Protease,as a kind of tenderizing-agents,can be used to improve tenderness of meat.Air-dried chickens,Chinese traditional dry-cured fowl products,are very popular among consumers,but few researches about them were found.The spent layers were tenderized by papain and processed into air-dried chickens by curing and air-drying and ripening in this study,which contains three parts.1.By L₉(3⁴) orthogonal experiment,the affect of papain-tenderizing on quality of air-dried spent layers products was researched by testing Warner-Bratzler Shear force (WBS),concentration of soluble protein(CSP),total of free amino acid(ΣFAA) of breast meat of air-dried spent layers products.The test factors were optimized.The results showed that WBS of breast meat of air-dried spent layers products significantly decreased(p＜0.05), CSP andΣFAA significantly increased with increasing amount of papain(p＜0.05). However,distasteful flavor was produced in the products when the amount of papain increased to 3.5 units per gram of raw material chicken.WBS of breast meat of papain-tenderizing group reduced 31.18%compared with the control,and CSP andΣFAA increased 16.59%and 22.24%respectively.The conditions of papain-tenderizing optimized were 2.5 units of papain per gram of raw material chicken,keeping papain-tenderizing for 30 min at 15℃.The experiment results were well consistent with the sensory evaluation.2.By two L₉(3⁴) orthogonal experiments,the affect of curing and air-drying and ripening on quality of air-dried spent layers products was researched by testing WBS,CSP,ΣFAA,NaC1 content and TBARS value in muscle of breast meat of air-dried spent layers products.The test factors were optimized.The results showed that parameters(cured temperature and time and concentration of NaC1 of curing solution) of curing had no significant effect on WBS of breast meat of air-dried spent layers products(p＞0.05);ΣFAA of breast meat of air-dried spent layers products significantly increased while cured temperature rose(p＜0.01,r=0.871),butΣFAA reduced while concentration of NaCl of curing solution rose;WBS of breast meat of air-dried spent layers products significantly decreased(p＜0.05,r=-0.508),ΣFAA significantly increased(p＜0.01,r=0.594)and value of TBARS in muscle firstly increased then fell while temperature of air-drying and ripening rose.The conditions of curing optimized were as follows:the spent layers were cured at temperature of 15℃for 24 hours in curing solution with 12%concentration of NaCl. Procedure of temperature and RH of air-drying and ripening optimized were as follows: 15℃-65%RH-21.5 h,17℃-71%RH-21.5 h,19℃-68%RH-21.5 h,21℃-63%RH-21.5 h.3.Volatile flavor components of breast meat of air-dried spent layers products were detected by method of HS-SPME-GC-MS,and the data were analyzed by principal component analysis to research flavor identity of air-dried spent layers products and function oftenderization to flavor of air-dried spent layers products.As a result,thirty three components were identified,and Aldehydes,Ketones and Alcohols were its main components,their relative amounts of volatile flavor components of breast meat of air-dried spent layers products were higher than those in air-dried goose;Relative amount of 3-methyl-butanal in breast of cooked air-dried spent layers products tenderized by papain was significantly more than that in cooked samples without tenderizing by papain due to the function of papain(p＜0.05),however,there was not significant difference between total volatile flavor components of them(p＞0.05);Volatile flavor components in breast of cooked air-dried spent layers products were apparently higher than that in breast of raw air-dry chicken products.