| The aged pork fat is the core component in the production of Chi-aroma Baijiu(CAB).During the long-term soaking process of pork fat,a large number of aldehydes,acids and esters are produced due to the lipid oxidation and play key roles in the formulation of the typical aroma of CAB.Using the traditional technology,pretreated fresh pork fat can be preliminarily used to produce CAB after being soaked in basic liquor for 6 months,while another 2-3 years soaking is needed to become high-quality aged pork fat.Up to now,the change rules of lipid oxidation products and rate-limiting reactions in the process of soaking pork fat are still not clear.Therefore,it is difficult to develop new technology which can greatly improve the productivity of aged pork fat.In this paper,two key rate-limiting reactions which restricting the oxidation efficiency of pork fat were found by exploring the change rules of lipid oxidation indicators,and the solutions to significantly accelerate the production of aged pork fat were given.Results are as follows:(1)The off-odor of raw pork fat could be eliminated by warm water and then boiling water pretreatment.In the soaking process of pork fat,polyunsaturated fatty acids(PUFAs)were the main reactants,which were easily oxidized to lipid peroxides.Aldehydes were produced due to decomposition of lipid peroxides and then oxidized to acids.Finally,carboxylic acids reacted with ethanol in basic liquor to form ethyl esters.These aldehydes,acids and esters provided aromatic components for the ageing of basic liquor.In the reaction steps mentioned above,the oxidation of unsaturated fatty acids(UFAs)to lipid peroxides and aldehydes to acids were two rate-limiting steps in the production process of aged pork fat.(2)Indoor illumination,sunlight,hydrogen peroxide and lipoxygenase could accelerate the oxidation of UFAs to lipid peroxides.Treatment of indoor illumination was the most ideal solution to alleviate the first rate-limiting step.The peroxide value(PV)and p-anisidine value(AV)of pork fat treated by indoor illumination reached 76.72 ± 2.98 g/100 g and 19.65 ± 0.96 respectively,which were 16.27 and 28.40 times than those of the control group.And the content of PUFAs increased to 19.06 ± 0.02 g/100 g compared with the control group.(3)Soaking with fat oil of high acid value was an effective way to alleviate the second ratelimiting step.The highest acid value of fat oil used in this research was 33.48 mg/g.The acid value of pork fat soaked with this fat oil was significantly increased to 5.46 ± 0.17 mg/g after 2-month soaking,which was 7.91 times higher than that of the control group.Fat oil could also promote the lipid oxidation of pork fat.The PV and AV of pork fat soaked with this fat oil were significantly higher and the PUFAs was significantly lower than that of the control group.According to the results,theoretical basis and feasible schemes for improving the soaking efficiency of pork fat were provided,which had a broad application prospect in the CAB industry. |
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