Cr 400 410

For the color analysis, a separate batch of chicken wingettes not inoculated with C. jejuni was allocated and coated with treatments as mentioned above. Following air-drying of wingette samples, color of the samples was measured using a chroma meter (CR 400/410, Konica Minolta Sensing Americas, Inc., Ramsey, NJ) as described previously (Wagle et al., 2017a (link)). The chroma meter provides information about 3 different colors (L, a, and b indicating relative lightness, redness, and yellowness, respectively). The instrument was calibrated against a tile, and average color values were recorded from 3 different locations on each sample. The samples were then vacuum-sealed to store at 4°C.

The color of the apple slices was measured using a colorimeter (CR400/410, Konica Minolta, Shanghai, China). The colorimeter was first calibrated and then used to determine the color value of fresh and dried apple slices. All color measurements for each apple slice sample were performed in triplicate and averaged for calculation. Equation (1) was used to compute the overall color difference of the apple slices [26 (link)].
$$\Delta E_{\mathrm{apple}}=\sqrt{{(L_{{\mathrm{apple}}_0}^{*}-L_{{\mathrm{apple}}_1}^{*})}^2+{(a_{{\mathrm{apple}}_0}^{*}-a_{{\mathrm{apple}}_1}^{*})}^2+{(b_{{\mathrm{apple}}_0}^{*}-b_{{\mathrm{apple}}_1}^{*})}^2}$$
where $\Delta E_{\mathrm{apple}}$ is the overall color difference value; $L_{{\mathrm{apple}}_0}^{*}$ , $a_{{\mathrm{apple}}_0}^{*}$ , and $b_{{\mathrm{apple}}_0}^{*}$ are the brightness, redness/greenness, and yellowness/blueness values of fresh apple slices, respectively; and $L_{{\mathrm{apple}}_1}^{*}$ , $a_{{\mathrm{apple}}_1}^{*}$ , and $b_{{\mathrm{apple}}_1}^{*}$ are the brightness, redness/greenness, and yellowness/blueness values of dried apple slices, respectively.

Colour changes on each apple fruit exposed to VUV and control were measured based on Commission International del’ Eclairage (CIE) colour system using a digital Chroma-meter (CR 400/410 Konica Minolta Sensing Inc., Japan). Colour calibration of the chroma-meter was performed against a white and black tile background before each measurement. Colour measurements were taken using individual fruit $\left(n=6\right)$ and data obtained were average of individual colour parameters. To describe the measured colour attributes hue angle $\left(h^0\right)$ , which describes the qualitative attribute of colour shades (0° red–purple and 180° bluish-green), and Chroma (C*), which denotes the quantitative attribute of colour intensity were calculated using Eqs. (4) and (5): $$h^0=ta{n}^{-1}\left(\frac{b^{\ast }}{a^{\ast }}\right)$$ $$C^{\ast }=\sqrt{{\left(a^{\ast }\right)}^2+{\left(b^{\ast }\right)}^2}$$ where, L^* denotes the lightness, $a^{\ast }$ describes red ( +)/green (−) and $b^{\ast }$ describes yellow ( +)/blue (−).

The color of the films was determined on the CieLab scale by means of a colorimeter, model CR-400/410 (Konica Minolta, Foster City, USA). The parameters L* a* and b* were evaluated. The L* component corresponds to the luminosity. It ranges from 0 to 100 to describe the black and white color, respectively. The a* parameter describes the red (positive value) and green (negative value) colors. For the b* parameter, the positive values represent the yellow color, while negative values correspond to the blue color.

The firmness of the entire fruit was non-destructively measured using a method adapted from Tijskens [45 ]. A fruit hardness tester (FHM-1, Takemura, Japan) calibrated with a 1 kg weight and equipped with a 12 mm diameter probe was used. Seven readings were obtained for each fruit at two pared surfaces on the equator and recorded in units of N/cm² after a controlled deformation. The SSC and the rind color were determined based on a method adapted from Liu [25 ]. The SSC of each melon was also measured by dropping the extracted juice from the equatorial region of flesh tissue onto a digital refractometer (DBR45, Huixia, Fujian, China). The rind color was detected using a chromatic color difference meter (CR—400/410, Konica Minolta, Japan); corresponding points on the fruit rind equator were detected, and seven values were recorded. Among these values, L* represents the brightness of the rind, which directly correlates with the fruit luster; a* represents the red/green ratio: higher positive values indicate red fruit, whereas negative values indicate green fruit; and b* represents the yellow/blue ratio: higher positive values indicate yellow fruit, whereas negative values indicate blue fruit. Each experiment was performed in triplicate.