A simple multiple linear regression model in near infrared spectroscopy for soluble solids content of pomegranate arils based on stability competitive adaptive re-weighted sampling

The objective of this study was to develop a multiple linear regression (MLR) model using near infrared (NIR) spectroscopy combined with chemometric techniques for soluble solids content (SSC) in pomegranate samples at different storage periods. A total of 135 NIR diffuse reflectance spectra with the wavelength range of 950-1650 nm were acquired from pomegranate arils. Based upon sampling error profile analysis (SEPA), outlier diagnosis was conducted to improve the stability of the model, and four outliers were removed. Several pretreatment and variable selection methods were compared using partial least squares (PLS) regression models. The overall results demonstrated that the pretreatment method of the first derivative (1D) was very effective and the variable selection method of stability competitive adaptive re-weighted sampling (SCARS) was powerful for extracting feature variables. The equilibrium performance of 1D-SCARS-PLS regression model for ten times was similar to 1D-PLS regression model, so that the advantage of wavelength selection was inconspicuous in PLS regression model. However, the number of variables selected by 1D-SCARS was less to 9, which was enough to establish a simple MLR model. The performance of MLR model for SSC of pomegranate arils based on 1D-SCARS was receivable with the root-mean-square error of calibration set (RMSEC) of 0.29% and prediction set (RMSEP) of 0.31%. This strategy combining variable selection method with MLR may have a broad prospect in the application of NIR spectroscopy due to its simplicity and robustness.

Effects of Argon-Based and Nitrogen-Based Modified Atmosphere Packaging Technology on the Quality of Pomegranate (Punica granatum L. cv. Wonderful) Arils

Ready-to-eat pomegranate arils are considered a “functional food” for their health benefits and have desirable sensory characteristics, which have caused an increasing interest by the consumers for this product. The preparation process of ready-to-eat fruit products can cause severe injuries and worsen their quality and shelf life significantly. Modified atmosphere packaging (MAP) has been used broadly in the last years to maintain the quality of processed fruits and showed optimal results, in spite of the possible problems caused by the depletion of O2 and corresponding accumulation of CO2 in the package. This study was conducted to evaluate the effects of different MAP treatments, based on nitrogen or alternatively on a noble gas, argon, in combination with refrigerated storage (0, 4, 8, 12, and 16 days at 4 ± 1 °C and 90 ± 5% RH) on the qualitative parameters of pomegranate arils with the aim to prolong their post-harvest life maintaining the original quality. The argon-based MAP treatment (MAPAr) was the one that provided the best results, assuring a limited loss of weight and juice content. The use of noble gas allowed to maintain a high sugar/acid ratio until 16 days from packaging. Sensory analysis on all MAP treated arils and, on the juice, obtained from them were carried out, and judges showed a preference for MAPAr treated arils and juice until day 12 from packaging.

Determination of drying kinetics, specific energy consumption, shrinkage, and colour properties of pomegranate arils submitted to microwave and convective drying

In this study, the drying kinetics, effective moisture diffusivity (D eff), specific energy consumption (SEC), colour, and shrinkage (S b) of pomegranate arils were compared when dried by convective (CV) drying and microwave (MW) drying. The experiments were performed at air temperature of 50, 60, and 70°C and air velocity of 1 m/s for CV drying and 270, 450, and 630 W for MW drying. The results showed that increasing air temperature and MW power increased the D eff. The calculations demonstrated that the maximum D eff for pomegranate arils was obtained for MW drying (630 W). Maximum SEC for pomegranate arils in the CV dryer was 145.12 kWh/kg, whereas in the MW dryer was 35.42 kWh/kg. In MW dryer, the lowest values of colour change and shrinkage were 6.77 and 50.5%, respectively. Comprehensive comparison of the different drying methods (MW and CV) revealed that MW drying had best drying performance for pomegranate arils, considering the drying time, effective moisture diffusion, SEC, colour, and shrinkage.