| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 103 === Food fermentation is one of the oldest food processing and preservation methods. Glucono-δ-lacton (GDL) and citric acid have been applied in the meat industry to improve flavors and extend shelf life of fermented products. However, too excess addition of GDL might deteriorate the qualities of products. The objective of this study was to investigate the influence of adding different amounts of GDL and citric acid on the physicochemical, microbiological, textural, and sensory properties of Nham sausages which inoculated with Lactobacillus plantarum as a starter culture.
The results showed that the pH values decreased significantly (P < 0.05) after finishing of fermentation (day 4), whereas no significant difference in pH values and water activity between treatments was observed during storage. The acidity increased dramatically during fermentation and then increased steadily thereafter and the control had the lowest acidity. Addition higher levels of GDL and citric acid tended to have higher acidity but there was no significant difference between treatments (P > 0.05). The L* and a* values did not significantly differ at day 0 and tended to increase after finishing of fermentation. Less change was observed in b* value after fermentation and during storage. There was no significant difference on b* values between treatments (P > 0.05) and they tended to decrease after storage. For the texture profile, the hardness, springiness, fracturbility and chewiness of samples increased significantly after fermentation, yet the cohesiveness of samples did not significantly differ between days 0 and 4. The hardness of samples did not significantly differ during storage. The control had the highest hardness whereas the ones with addition of GDL and citric acid had lower hardness. The VBN values increases significantly during the fermentation (P < 0.05). The control had the highest VBN values, followed by the ones with addition of citric acid; the more with addition of GDL, the less of the VBN values. The counts of total viable bacteria and lactic acid bacteria counts increases rapidly during fermentation and there was no significant difference between treatments (P > 0.05). There was no significant difference on the sensory characteristics between treatments. The NPN values of all treatments increased rapidly during the fermentation, and the ones of GDL04+CA01 and GDL08+CA01 decreased during storage. For the SDS-PAGE, the intensity of the myosin heavy chain (MHC) band decreased thereafter. The actin band (around 45 kDa) also decreased in intensity after fermentation and storage. In conclusion, adding GDL and citric acid did not detriment the physicochemical, microbiological, and textural qualities of the Nham sausages inoculated with L. plantarum. Further studies should be addressed on the protectium against the pathogens base on the addition of GDL and citric acid in order to produce safe Nham sausage with better qualities.
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