Study On The Pineapple Fruit Vinegar Brewed From Pineapple Peel

Pineapple peel is the waste of pineapple processing. As its nutrition is similar with pineapple pulp, so it has a great value of further processing. Pineapple peel can be brewed into fruit vinegar, which not only can solve a lot of pineapple processing wastes that caused environmental pollution and resource-wasted problems, but also promote the added value of pineapple processing, and enhance the development of the pineapple industry. Pineapple fruit brewed from pineapple peel using liquid fermentation was studied in this thesis, including pre-processing technology, optimization of fermentation conditions, evaluation of the quality of fermented pineapple vinegar and analyzing flavor compositions of the fermented pineapple vinegar, which could be a theoretical support for the deeply processing of pineapple vinegar and its industrialization.Four fermentation manners (pineapple peel juice-natural fermentation, pineapple peel juice-inoculation fermentation, pineapple peel pulp-natural fermentation and pineapple peel pulp-inoculation fermentation) were studied. Results showed that pineapple peel juice-inoculation fermentation is the better fermentation manner, as pineapple vinegar brewed by this fermentation manner showed the better sensory evaluation, highest alcohol and acetic acid production (5.7% and 3.93g/100mL).Three juice-extraction methods (hot-extraction, fresh-extraction and enzyme-extraction) were studied. Results showed that the enzyme-extraction is the best juice-extraction technology. Optimization of enzyme-extraction conditions were further studied and results showed that dose of pectinase is 0.2%, time of pectinase reaction is 3.5h, temperature of pectinase reaction is 45℃, pH of pectinase reaction is 4.0. Juice yield is about 72.71% when extracted under optimal conditions.Multi-strain fermentation was studied. The results showed that the best quality of pineapple vinegar was got when the proportion of beer yeast to aroma yeast was three to one, and product contented higher alcohol and rational esters, and smelled aromatic.Response Surface Analysis was used to optimize fermentation conditions in this thesis and the results are as follows: (1) The most optimal process parameters of alcohol fermentation are as follows: temperature of fermentation is 23.1℃, pH 3.74, initial sugar 17%, inoculum size of ber yeast 3.3% and aroma yeast 1.1%. (2) The most optimal process parameters of acetic acid fermentation are as follows: initial alcoholicity is 7.2% (v/v), temperature 30.3℃and inoculum size of acetic acid bacteria 7.2%. Degree of acidity was got about 4.7g/100mL when fermented under optimal conditions.Sensory evaluation of pineapple vinegar had been made and its physicochemical and microbiological indexes detected. Results showed that sensory, physicochemical and microbiological indexes completely met the government standard.36 kinds of flavor components in the pineapple fruit vinegar were identified for the first time by the analysis of gas chromatography-mass spectrometry. 13 kinds of them were identified as easy-volatile flavor parts and the others were hard-volatile parts. In the easy-volatile flavor parts, acids accounts for 41.776%, alcohols 3.15%, aldehydes 0.102%, esters 44.069% and hydrocarbones 7.065%. In hard-volatile parts, acids accounts for 6.227%, alcohols 25.21%, aldehydes 0.658%, esters 41.043%, Phenols 5.321% and the other flavor components 4.009%. These components formed the particular flavor of pineapple fruit vinegar.