Investigation Color Changing Sour Orange Juice during Ohmic Heating Process by Response Surface Method

Sour orange (Citrus aurantium L.) synonymous with the name "C. bigaradia Duh, C. Vulgalis" is native to Southwest Asia, and it has a rounded and acidic fruit known as bitter sour orange, sour orange or Seville names. It is also necessary to process food products, one of which methods is the thermal processes based on heat transfer mechanism via conduction, convection and radiation. Given that color is one of the appearance characteristics of food products for customer selection and marketability, in this study, an ohmic heating system in three input voltage gradients (8.33, 10.83, 13.33 V / cm) and three percent weight loss (10, 20 and 30%) of the total weight made in the heating process. After the heating process, color change was performed using Image J software and the factors L *, a *, b *, BI, C, TCD were measured and the results were analyzed using the response surface method. The results showed that for L *, b *, browning index, chroma index and TCD had the highest estimation coefficient for weight loss percentage and for a * value of process voltage had the highest estimation coefficient. Also, except for the factor a *, where the quadratic model is suitable for the two model factors, for the other factors, the linear model is obtained against the mean of the appropriate model by the response surface.