Effect Of Enzymatic Hydrolysis On Natural Milk Fat Composition And Flavor

Milk fat, owing to its buttery sense and fragrant aroma, is widely used in such foods as bakery food, coffee, ice cream, candy, drink, etc. However, the volatile aroma of milk fat is mainly related with fatty acids, ketones, aldehydes, and lactones, which are apt to losses in the course of food processing, especially in heating up and sterilization. The main aim of this work is to improve the flavor of milk fat by increasing the content of short- and medium-chain fatty acids by means of lipase catalyzed hydrolysis.SPME coupled with GC-MS was used to inspect the volatile milk fat aroma. The optimum parameters of SPME were determined: PDMS/DVB extraction fiber, use of stirrer, 60℃, and 4h. The flavor components identified by GC-O analysis. Ten compounds contributed to the flavor of milk fat including octanal(fruity), 2-nononone (winey), ethyl carpylate(buttery), butanoic acid (buttery, a little sour), pentanoic acid(buttery), 2-tridecanone(wood-like), hexanoic acid(buttery, slightly sour), heptanioc acid (buttery, slightly sour), octanioc acid (flower-like, slightly winey), and an unknown compound (buttery, winey, supposed to be an aldehyde).The conditions of enzymatic hydrolysis of milk fat were optimized by means of the Response Surface Methodology(RSM): Palatase 20000L, 45℃, 4h, enzyme addition 0.08%, oil/water ratio 20g:20ml.It was identified from the comparison of fatty acid and flavor component pattern of milk fat before and after enzymatic hydrolysis that the composition of fatty acid was little changed while the content of key flavor compounds in the volatile compounds of milk fat was increased after enzymatic hydrolysis. The content of key flavor compounds increased from 51.25% to 69.02%.Sensory evaluation and baking tests of the natural and hydrolyzed milk fat were conducted and the results was analyzed by Fuzzy Synthetic Evaluation. It was indicated that the texture and color of milk fat were not changed notablely, but the flavor was improved after enzymatic hydrolysis. The rigidity and texture of bakery food is little influenced, while the aroma and sense of mastication is improved.