| Summary: | 碩士 === 國立中興大學 === 食品科學系 === 92 === Abstract
The apple juice concentrates (AJC) produced from Shandong and Henan (China) was used as materials to study their quality changes during storage at different temperatures. In addition, quality improvement was also conducted by decolorization and adding food chemical additives.
The average temperatures of the inside containers transported from Shandong and Henan (China) to Taichung (Taiwan) from June to October in 2003 were higher than 40℃ while the highest and lowest temperatures were 48 and —6℃, respectively. The temperatures, 37, 45 and 55℃ were chosen as the experimental temperatures, and the storage time was set as 20 days. During storage at high temperature, the intensity of browning of the AJCs from Shandong and Henan increased with the time while the transmittance of the AJCs decreased. During the storage period, 5-hydroxymethyl-furfural (5-HMF) accumulated in the AJC samples at 45 and 55℃ but no apparent change was observed at 37℃. No apparent changes in the concentrations of fructose and glucose as well as their ratio were noted under different temperatures and times during storage. But under the same condition, the sucrose content decreased as the storage time increased. It was inferred that the sucrose was degraded for the Maillard reaction. For the free amino acids, the changes in the contents of Glu, Gly, Leu and Tyr were found to be the highest. After stored at 55℃ for 20 days, Glu, Lys, and Tyr were completely degraded, and the changes in the contents of the other amino acids ranged from 50 to 58%. The changes in the amino acids were different between the AJCs from Shandong and Henan. Glu, Gly, Leu and Tyr were the major amino acids in the Shandong AJC to be affected while Glu, Ser and Thr were the major amino acids in the Henan AJC being affected. According to the experiment, no apparent changes in the organic acids and microbiological growth were found in both two AJCs.
The treatments of the addition of chemical additives (e.g. ascorbic acid, erythorbic acid, and potassium meta-bisulfate) and decolorization (absorber resins and activated carbon) were conducted in order to improve the color quality of AJCs during transportation. It was found that the addition of ascorbic acid, erythorbic acid, and potassium meta-bisulfate could not reduce the Hunter color value (L, a, the b value) and improve the color quality of AJCs during storage at 45 and 55℃for 20 days as compared with commercial specifications. By adding absorber resin and activated carbon into the ACJs, the color quality of AJCs were improved to reach the international commercial standards (browning indexes < 0.5; transmittance > 92%) after stored at 37 and 45℃ for 20 days. Moreover, the results indicated that resin treatment could decolorize the ACJs to match the commercial standard of Taiwan (browning indexes < 0.35; transmittance > 92%), suggesting that absorber resin was better than activated carbon in decolorization. For the storage at 55℃, both the absorber resin and activated carbon could merely improve the color quality to a level below the commercial standard, indicating that decolorization did not work properly for the samples treated by relatively high temperature. Without decolorization treatment, the degradation of free amino acids such as (Asn, Asp, Ile, and Arg) led to the browning of the ACJs. Accordingly, the reduction in the levels of Asn, Asp, Ile, and Arg after proper decolorization treatment declined the Maillard reaction and improved the color quality of the ACJs. Furthermore, the amounts of 5-HMF accumulated in the ACJs stored at different temperatures (37, 45, and 55℃) were also reduced by the decolorization treatment.
Based on the results of this study, the qualities of AJCs in terms of
color and composition were deteriorated when stored at 45 and 55℃. The treatments with both absorber resins and activated carbon can effectively improve the color degradation of apple juice concentrate. The treatment of absorber resins is more efficient than that of activated carbon. The data obtained from this result provide useful information for the quality control of apple juice concentrate during transportation.
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