Characterization of Mixed Apple and Carrot Retentates Using Response Surface Methodology

Models capable of predicting the product quality of mixed apple and carrot retentates (MACR) have been developed using response surface methodology and used to characterize the effects of processing conditions including average transmembrane pressure (ATP), temperature, and blend ratio. Color, soluble solids, total sugar, vitamin C, acidity, turbidity, and viscosity were used to assess the product quality following the ultrafiltration (UF) process. $L^*-value$ decreased with increased ATP, but the value was not affected by changes in temperature. Blend ratio also greatly influenced the $L^*-value$. Redness ($a^*-value$), on the other hand, was less affected by temperature and ATP. As the ATP and temperature increased, yellowness increased gradually. Soluble solids contents appeared to decrease gradually as the ATP increased for all blend samples, but the effect of temperature seemed to be less. Total sugar content was more affected by temperature than ATP. In general, samples containing 75% carrot had higher amounts of vitamin C regardless of processing conditions. Changes in acidity were also complex and appeared to respond to interactions among ATP, temperature, and blend ratio. Turbidity increased for all samples as both ATP and temperature increased. The higher the amount of carrot in the blend samples, the higher values for turbidity. Although the changes were small, viscosity appeared to increase as the ATP and temperature increased during UF.