Objective quality assessment of modified atmosphere stored zucchini slices using electronic nose, machine vision and instron

Modified Atmosphere Storage (MAP) is an important method to extend shelf life of food. Using electronic nose (EN), machine vision (MV) and Instron provides quality evaluation of foods. Our objective was to measure quality changes of MAP stored sliced zucchini using EN, MV and Instron, and correlate these data with sensory parameters and microbial counts. Zucchini were washed, sliced, and dipped in chlorinated water for 2 min, and spin-dried. During the controlled atmosphere (CA) study, containers were attached to the flow-through system during storage (10°C, RH = 95%). Samples were subjected to 2 different CA conditions (2%O₂ + 7%CO₂ and 2%O₂ + 15%CO ₂, balance N₂) and air. During the first and second studies, slices were put into two different plastic bags (∼280g/bag). Bags (P1 = first bag; P2 = second bag) were flushed with gas (2%O₂ + 15%CO₂ balance N₂, or air), sealed and stored (5°C, RH = 95%). Samples were evaluated using EN, MV and Instron, and sensory quality parameters. Aerobic microbial counts were performed. EN and MV data were evaluated by discriminant function analysis (DFA). Correct classification rates (CCR) and cross validation analysis were performed. Canonical correlation was calculated between objective readings and sensory evaluations.; CCR for color data were 100% for air, 7% and 15%CO₂ treatments for the CA experiment. CCR for P1-Air, P2-Air, P1-CO₂ and P2-CO ₂ were 96%, 98%, 97%, and 98%, in the first experiment and 88%, 96%, 94%, and 93%, in the second experiment, respectively. DFA of EN data gave more than 98%, 94% and 96% CCR for all treatments in CA, first and second experiments, respectively. MAP significantly reduced microbial growth, discoloration and off-odor, and maintained hardness, crispness and zucchini aroma (p > 0.001) for CA and second experiment. Average L* a* b* values and % color changes showed that the best color preservation was with CO₂ treatments. The correlations among different color blocks, e-nose sensor readings, textural parameters, and microbial loads with different sensory attributes were significant. This project suggests that the use of objective methods, correlated to sensory results, can save time, cost, and increase reliability of food quality evaluation.