The Relationship Between Goaty Flavor And The Volatile Substances Of Goat Milk

The goat’s milk containing protein, fat, minerals, vitamins and a variety of bioactive substances, which were known as "the king of milk" in the world. But the goaty flavor makes some people don’t like to drink goat milk, which limits the development of goat milk industry. Numerous studies show that goaty flavor is closely related to its chemical composition, especially the volatile constituents. Thus, the present study was to analyzed relationship between volatile components and the goaty flavor for goat milk and goat milk powder, which in order to investigate the mechanism of the improvement of the goaty flavor by fermentationThe paper is mainly divided into three parts.The first part:To established condition of headspace solid phase extraction of micro volatile components for goat milk. Head space solid phase micro-extraction (HS/SPME) coupled with gas chromatography (GC) were used for the determination of volatile compounds in goat milk. HS/SPME experimental parameters, such as SPME fibre, extraction temperature, NaCl concentration, extraction time and desorption time were optimized using the number and area of peaks as index. The optimal extraction efficiency for goat milk was achieved when sample was headed at 70℃ for 90min after the addition of 0.3g/mL NaCl, extracted by a carboxen/polydimethylsiloxane (CAR/PDMS) fibre, and than the fibre was transferred to a GC injection port for thermal desorption at 250℃ for 5 min.The second part:The relationship between volatile components of goat milk and goaty flavor was studied. The main factors affecting the goat milk flavor were analyzed, for exploring the possibility that causing the goaty flavor, also for providing a therotical basis for the development and utilization of goat milk. Head space solid phase micro extraction were used for extracting the volatile components from 15 different odor intensity goat milk samples, and then the volatile components were separated and detected by gas chromatography-mass spectrometry. Principal component analysis and correlation analysis were used for assessing the goaty flavor quality. The results indicate that 49 kinds of volatile components were detected from goat milk of 15 samples, and that including acids (12 kinds), hydrocarbons (9 kinds), aromatic (8 kinds), ketones (5 kinds), alcohols (7 kinds), esters (3 kinds), aldehydes (2 kinds) and other components (7 kinds). The maliy goaty flavor substances are 4-methyl octanoic acid and n-nonanoic acid. Therefore, principal component analysis coupled with correlation analasis has the potential to be used for goaty flavor quality evaluation of goat milk, and was established evaluation model for the goaty flavor (GF=6.3575x39+4.2273x40+4.0595, and GF represents of the goaty flavor value, and x39 represents the relative content of 4-methy caprtlic acids, and x40 represents the relative content of pelargonic acids, and the correlation is 0.72, p<0.01).The third part:Study on the changes of volatile components and goaty flavor for goat millk powder under different storaged temperatures. We used HS/SPME method and GF value to analies the goat milk powder, which were storaged at 5℃,25℃ and 35℃. The results show that,37 kinds of volatile components were detected from the goat milk powder that were storaged at 5℃, and that including acids (11 kinds), esters (5), hydrocarbons 50 kinds), alcohols (4 kinds), aldehydes (3 kinds), and other components (9 kinds); 46 kinds of volatile components were detected from the goat milk powder that were storaged at 25℃, and that including acids (14 kinds), esters (5), hydrocarbons (7 kinds), alcohols (5 kinds), aldehydes (3 kinds), and other components (12 kinds); 49 kinds of volatile components were detected from the goat milk powder that were storaged at 35℃, and that including acids (13 kinds), esters (6 kinds), hydrocarbons (8 kinds), alcohols (6 kinds), aldehydes (9 kinds), and other components (7 kinds).And than we used the GF values to analysis the goat milk powder goat flavor change that storage at 5℃,25℃ and 35℃. The results show that 25℃ and 35℃ were not for stroge of goat milk powder because of that goaty flavor changes rapidly. Therefore we should choose storage at 5℃ to extend the shelf life of goat milk powder.