The Effect Of Cooking Conditions And Distribution Methods On The Quality Of Traditional Braised Pork

In China, most of people like to eat pork, in addition to the individual nations. There are many methods to cook pork, and braised pork is one of the most famous among all. Braised pork is delicious and attracts many consumers. In this study, the streaky pork was used as raw materials, while yellow wine, onion, garlic and ginger were main condiment in order to study the volatile compounds of braised pork in the process stewing. Further, the fuzzy mathematic evaluation was carried on the optimization, and the characteristic flavor of braised pork was detected under the optimal conditions. In addition, the effect of cold/hot chain distribution on flavor and nutritional quality of braised pork was studied.1.Effects of the composite of ginger, onion and garlic on the volatile compounds of stewed-porkElectronic nose and gas chromatography-mass spectrometry (GC-MS) were used to analyze the effect of ginger, onion and garlic(OGG) on stewed-pork flavor. The sensory evaluation suggested that OGG could improve the sensory quality of stewed-pork and the 5% group was best. Both principal component analysis (PCA) and linear discriminant analysis (LDA) of the electronic nose data suggested that OGG had effect on the stewed-pork flavor. The electronic nose was able to detect a clearer difference in volatile profile of stewed-pork using LDA than using PCA. GC-MS analysis showed that the composition and proportions of volatile compounds of stewed-pork were greatly changed with the addition of OGG.40 kinds of major components were identified from the control group, mainly including alcohols (alcohol> 20%)> 35%, followed by ketons and aldehydes. Compared with the control group,49 kinds of major components were identified from the 5%OGG group, mainly including ketones (cyclohexanone> 20%)> 30%, followed byaldehydes and alcohols.12 and 11 key odor compounds (ROAV?1) were assigned by relative odor activity value (ROAV) in the control group and the 5% OGG group, respectively, including aldehydes, alcohols, esters and sulfurcontaining compounds.2-heptenal also had an important contribution to overall flavor of both of control group and the 5%OGG group (0.1?ROAV<1).2.Effects of Chinese rice wine on the volatile compounds change during the processing of stewed-porkElectronic nose and solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) were used to analyze the effectsof Chinese rice wine on the volatile compounds change during the processing of stewed-pork. Both principal component analysis (PC A) and linear discriminant analysis (LDA) of the electronic nose data suggested that Chinese rice wine had effects on the stewed-pork flavor. The electronic nose was able to detect a clearer difference in volatile profile of stewed-pork using LDA than using PCA (P<0.05).71 kinds of volatile components were identified from the stewed-pork by SPME-GC-MS, mainly including aldehydes,aliphatic hydrocarbons, alcohols,ketons and others. Aldehydes, especially hexanal were the most abundant among all compounds.13 key odor compounds (ROAV?1) were assigned by relative odor activity value (ROAV):(Z)-2-heptenal, (D)-limonene, heptanal, benzaldehyde, decanal, octanal?(E)-2-nonenal, 1-octen-3-ol, (E,E)-2,4-decadienal, hexanal. It could be known that the key odor compounds have more fat ordor than others. The 13 key volatile odor compounds could beclassified into 3 clusters by cluster analysis (CA), and the results showed (E, E)-2,4-decadienal and hexanal were the characteristic volatile compounds to identify the pork stewing with Chinese rice wine.3.Lipid oxidation, fatty acid composition and volatile compounds change during the processing of stewed porkLipid oxidation,fatty acid compositions and volatile compounds were detected in stewed pork during the whole processing including raw material, blanching, stewing 0.5h, 1.0h,1.5h,2 h as six key stages. The results showed that the degree of lipid oxidation increased significantly during the stewing process (P< 0.05). The ratio of saturated fatty acids (SFA) revealed a significant decrease (P<0.05), while unsaturated fatty acids (UFA) revealed a sharp increase (P<0.05) during cooking. UFA/SFA ratio was increased from 0.34 to 0.70, which improved the nutritional value of pork lipids. The main volatile flavor substances in stewed pork are aldehydes and alcohols, and the contents of them reached the peak level after stewing for 1h followed by decline.4.Process optimization and analysis of volatile flavor compounds of braised porkFuzzy mathematic evaluation model was introduced to optimize the process of braised pork. Volatiles in braised pork were investigated by solid-phase microextraction (SPME), coupled to gas chromatography-mass spectrometry (GC-MS). The optimum conditions are as follows:blanch time of 3 min, stewed time of 2.5h and stewed temperature of 100?. The SPME technique was previously evaluated to optimize conditions (incubation time,15 min; extraction temperature, 60?; extraction time,35 min). A total of 60 volatile flavor compounds were identified by GC-MS, including 10 aldehydes,10 alcohols,15 aliphatic hydrocarbons, 5 esters,7 ketons,7 compounds containing S?N and others. Aldehydes have the highest proportion (24.68%), following compounds containing S, N (20.99%) and aliphatic hydrocarbons (19.57%). Hexanal (0.72?g/g), limonene (0.51 ?g/g) and propylene sulfide (0.51 ug/g) are themost abundant among all compounds.5.Effect of different storage and reheating procedures on the lipid oxidation, volatile flavor compounds and fatty acid compositionsBraised pork was stored at hot chain condition (incubator,65?) for 5h and cold chain condition (fridge,4?) for 5 days, then reheated by micro waving and steaming in order to study changes occurring in the lipid oxidation, volatile flavor compounds and fatty acid composition. Peroxide value (POV),2-thiobarbituric acid (TBA), carbonyl value and diene value were measured to evaluate the lipid oxidation, suggesting that the degree of lipid oxidation significantly increased with the extension of storage time (P<0.05). The lipid oxidation existed significant differences between braised pork reheated by microwaving and steaming (P<0.05). Volatile flavor compounds in braised pork were investigated by SPME-GC/MS, and the results showedthat significant changes occurred in the volatile flavor compounds during storage, especially aldehydes and alcohols (P<0.05).Thecontent of total volatile flavor compounds (peak area) of braised pork stored in hot chainincreased first and then declined, whilebraised pork stored in cold chain then reheated by microwavingand steaming,respectively, showed an upward trend. GC was used to measure fatty acid composition of braised pork, showing that UFA/SFA increased and then decreased during hot chain storage, while UFA/SFA had a rise trend after reheating. Different storage conditions and reheating procedures had a significant effect on the nutrition and flavor quality of braised pork.