สมบัติและเสถียรภาพของมายองเนสที่ใช้น้ำมันผสมระหว่างน้ำมันมะพร้าวและน้ำมันรำข้าวเป็นน้ำมันพื้นฐาน / ศรุดา สถิตวรพจนา = Properties and stability of mayonnaise using oil blends between coconut oil and rice bran oil as oil base
The purpose of this research was to study the effects of replacement of coconut oil (CNO) (high content of Medium-Chain Fatty acids (MCFAs)) in rice bran oil (RBO) (high content of Long-Chain Fatty acids, LCFAs), which was used as oil base, on property and stability of mayonnaise. At the first part of the study, the fatty acid profile and properties of five ratios of oil blends (0:100, 10:90, 20:80, 30:70 and 40:60 (v/v)) such as color (CIE L*, a*, b*), viscosity and crystallization temperature (Tc) were studied. It was found that CNO had 61.25% MCFAs and 38.22% LCFAs whereas RBO had 99.99% LCFAs. Increase in CNO ratio in oil blend resulted in increases in MCFAs and lightness (L*) but decreases in redness (a*), yellowness (b*) and viscosity. Tc values of five ratios of oil blends were -12.9 °C, -13.0 °C, -14.6 °C, -6.5 °C and -5.6 °C, respectively. In the second step of the study, mayonnaise was prepared using 72% oil blends (five ratios), 1% salt, 10% egg yolk, 8% sugar and 7% vinegar (w/w). The properties of mayonnaise were evaluated on Emulsion Stability Index (ESI), color, firmness, consistency, cohesiveness, index of viscosity, microstructure, Tc, 2-Thiobarbituric acid (TBA) and sensory evaluations. It was found that the highest portion of CNO replacement in RBO was 30% (30:70) supported by the results of unchanged ESI values during two weeks of storage. The lightness (L*), firmness, consistency, cohesiveness and index of viscosity values were higher than 40:60 ratio but b* value was lower than 40:60 ratio. Moreover, a* value was not significantly different (p>0.05) with other ratios. The size of its droplet was smaller and demonstrated lower dispersion than those of the 10:90 and 20:80 ratios. Tc and TBA values were -9.8 °C and 0.27 mg malonaldehyde / kg, respectively. For this 30:70 ratio, the sensory evaluation result of the color was not significantly different (p>0.05) whereas the texture was accepted similar to 0:100 ratio, which was the most acceptance. The taste was accepted not significantly different (p>0.05) with those of 10:90 and 20:80 ratios. Moreover, overall acceptance was not significantly different (p>0.05) with those of 10:90, 20:80 and 40:60 ratios. At the final step of the study, the results from stabilities of storage mayonnaise, (0:100 and 30:70 ratios), which were stored at 30 ± 2°C for 4 weeks, demonstrated that those of 0:100 and 30:70 ratios had unchanged ESI values during 4 weeks of storage and their Tc values were similar to the beginning values of the storage. The amount of Total Viable Plate Count, Yeasts and Molds and Coliforms were lower than the recommended microbial standard values of the Thai Industrial Standard. During 4 weeks of storage, both 0:100 and 30:70 ratios had significantly decreased in L* and b* values while a* values decreased. The TBA value of 30:70 ratio increased during storage, while the TBA value of 0:100 ratio increased during 3 weeks of storage and then decreased in the last week. Increase in some droplet sizes of 0:100 ratio could be related to flocculation and coalescence of droplets. For 30:70 ratio, less change in droplet size was observed during the time of storage.