Effect of gelatin edible coating containing antioxidant agents on hardness, and color of roasted pistachio nuts

The present study investigated the effect of gelatin coating, containing ascorbic-acid (AA:1% w/v) and Propyl-gallate (PG:100ppm), on the instrumental and sensory properties of roasted pistachio (hardness and color). Pistachio nuts packed and stored at 35°C and 50 C. The changes occurred in the textural properties, moisture content, color parameter (‘L’, ‘a’ and ‘b’ values) and sensory attributes of pistachio nuts were determined during 3 months of storage. The instrumental properties were correlated with sensory attributes. Gelatin antioxidants coating significantly (P<0.05) increased instrumental and sensory hardness of pistachio. The moisture content decrease with time in gelatin-antioxidants and antioxidant-coated samples. However, this value in gelatin-coated samples was significantly lower than another sample. In sensory evaluation of color, the effect of treatments was significant. The image processing result revealed that color parameter a* in green kernel beside L* and b* parameter in purple skin of kernel, was significantly increased in AA-gelatin coated pistachio. Using the gelatinantioxidants coating, brought better maintenance to the green color of the kernel (the ΔE* factor lower than control sample) while it decreased the red-purple color of kernel skin (more ΔE* factor). The results indicated that there are strong relationships between the instrumental and sensory hardness values, but sensory and instrumental color values had a weak correlation with each other.