Application of simplex lattice mixture design for optimization of active modified atmosphere for pomegranate arils (cv. Wonderful) based on microbial criteria

Despite the advantages of low O-2 and enriched CO2 for extending the storage life of pomegranate arils, limited studies on systematic selection and optimization of gasses to reduce the microbial growth during storage have been reported. Therefore, this study was undertaken to optimize the gas composition for cold storage (10 degrees C) of pomegranate arils (cv. Wonderful) based on microbiological criteria. Selecting experimental points and optimizing gas concentration were carried out according to the simplex lattice mixture design with three factors (O-2, CO2 and N-2). Seven gas combinations including low O-2 (2-18 kPa), enriched and high CO2 (2-18 kPa) and 80-96 kPa N-2 were used in varying concentrations and the bacterial, yeast and mould growth on arils were analysed. Aerobic mesophilic bacteria growth varies between 3.95-5.89 log CFU g(-1) and yeast growth was between 3.84-5.91 log CFU g(-1), whereas, mould growth was between 2.15-3.63 log CFU g(-1) across the modified atmospheres. Data from these analyses were used to fit linear and cubical polynomial models. Pareto analysis and ternary contour plots showed that the main effects (CO2, N-2 and O-2) as well as their interaction had significant effects on microbial growth. For all microbial criteria's, the lowest growth was tend to move to the highest CO2 in the modified atmosphere system. On the contrary, the presence of higher O2 concentration stimulated the growth. This was evident that, the gas mixture containing 12.67-18 kPa CO2, 2-4.67 kPa O-2 and 80-82.67 kPa N-2 significantly reduced microbial count on pomegranate arils. Validation of the model showed that the cubical model predicted the microbial counts effectively with high correlation coefficients of R-2 > 94% for mould and > 99% for aerobic mesophilic bacteria and yeast, whereas, the linear model overestimated bacteria and yeast counts and underestimated mould count.