Investigation on aroma compounds of cocoa wine

• Main Authors: Jheng, Yu-Jing, 鄭榆靜
• Other Authors: Chiu-Hsia Chiu
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/3ptbyf

碩士 === 國立屏東科技大學 === 食品科學系所 === 105 === Cocoa beans (Theobroma cocoa L.) are the major raw material for producing chocolate by fermentation. Fermenting cocoa beans is an essential process for developing chocolate flavor, this process uses various strains of three main species include yeasts, lactic acid bacteria and acetic acid bacteria. Therein, Yeasts are necessary not only for the successful creating of different chocolate types with various flavors, aromas, but also essential for alcohol fermentation of cocoa wine. The principal objective of this study is to screen yeast strain which is most effectively on both the quantity and quality of alcohol fermentation. The Taguchi design will be used to optimize the conditions for producing cocoa wine. Then, the gas chromatography-mass spectrometry (GC-MS) will be used to find total concentration of aromatic compounds from cocoa wine production. In the first part, 54 yeast strains were isolated from Pingtung cocoa pulp. Then these yeasts were inoculated in Einhorn’s fermentation saccharometer, containing 20°Brix glucose solution. The yeasts were also compared by ethanol tolerance and fermentation rate test. In the second part, volatile aroma compounds were analyzed by GC-MS with Solid Phase Microextraction (SPME) and being discussion on the optimum analysis conditions of cocoa wine with different extraction conditions, investigation of the fiber (100 μm PDMS, 50/30 μm DVB/CAR/PDMS and 85 μm Carboxen/DVB), the water bath temperatures (30, 40 and 50℃), the adsorption periods (40, 50, and 60 min), and the desorption time (5 and 10 min). In the third part, Taguchi method was used for optimizing the total concentration of aroma compound which was analyzed by HP-SPME-GC-MS. The 20% cocoa pulp was added into different conditions of sucrose concentrations (15, 20 and 25° Brix), C16 yeast inoculum sizes (1, 3 and 5%), temperatures (20, 25, 30℃) and the fermentation period (7, 14 and 21 days). In the fourth part, the aroma components in cocoa wine which made with different strains (S. cerevisiae P13, P. kluyveri IB8 and S. cerevisiae C16) were explored, and the cocoa wine made by different brewing methods was used for sensory evaluation. In the fifth part, the cocoa distilled wine was aging at 10℃ as ambient temperature for 14 days, the aroma compound of three brandy kinds were then compared. The result showed, among the 54 yeasts tested, 6 yeasts strains showed better fermentation capacity, which include; C5, C6, C16, C19, C28 and C30. Upon ethanol treatment, the survival cell counts of these 6 selected strains all decreased with increasing ethanol concentration. However, C16 can tolerate ethanol concentration up to 12%, and in different saccharide solution fermentation test, it pointed out that C16 fermentation more stable than others, therefore C16 was used as only strain in follow up test. The optimized sorption and desorption conditions were summarized as follows: 10 mL sample of cocoa wine was evenly spread on DVB/CAR/PDMS cloth with 50/30 μm coating thickness, then was heated in 30℃ for 50 min, and followed by desorbing at 250℃ for 5 min. The result showed that with the optimum fermentation condition of 20°Brix sucrose, 5% inoculation size, fermented temperature 20℃ and fermented period 14 days, the total aroma compound concentration reached 2353.06 ± 189.09 (ppm), and the 22 aroma compounds have found which was determined as Isobutanol, Isoamyl alcohol, Ethyl Acetate, Isoamyl acetate, Ethyl hexanoate, Ethyl octanoate, Ethyl decanoate. The ratios of esters to alcohols is 1.23±0.20. The confirming test showed a similar result with ethanol concentration up to 9.25%. In the sensory evaluation, the color of the roasted cocoa bean wine is favorable, although its taste is more astringent and bitter than others. In the overall, the cocoa pulp wine is the most preferable by wine tester. Based on the above experiment results, S. cerevisiae C16 shows a high potential for cocoa wine making with high quantity of alcohol content and high quality of aroma compound and its taste.