Cr 300 measuring head

The olive colour was assessed by taking at least 10 random measurements from the surface of different olives using a Minolta Chroma Meter fitted with a CR-300 measuring head (Minolta, Osaka, Japan). The CIE (Commission Internationale de l' Eclairage) L*, a*, b* colorimetry system was used for colour determination. L* indicates lightness, and its values range from 0 (an ideal black object) to 100 (an ideal white object). Positive a* values indicate red direction, negative a* value is the green direction, positive b* values are the yellow direction, and negative b* values are the blue direction. The instrument was calibrated with a standard white tile (L* = 96.10, a* = +0.98, and b* = +7.27). At each sampling time, 10 olives from each sample (package) of each different treatment were analyzed in duplicate (2 measurements at random locations on each olive). Thus for each time point and treatment a total of 120 measurements were recorded (3 batches × 2 samples × 20 measurements). Chroma (C*) and hue angle (h*) values were also calculated based on the following equations:
$\begin{array}{c}{C}^{\ast }=\sqrt{a^{\ast \mathrm{2}}+b^{\ast \mathrm{2}}},\\ h^{\ast }={\tan }^{-\mathrm{1}}\left(\frac{b^{\ast }}{a^{\ast }}\right).\end{array}$

The pH value of the samples was recorded with a digital pH meter (HI 2211 pH-ORP Meter, HANNA Instruments, Woonsocket, RI, USA), during storage at different temperatures at different time intervals. After finishing the microbiological analysis, the ham homogenate (stomacher homogenate) was used to measure the pH of the samples.
The color of the ham samples was evaluated by taking at least five random readings from the surface of the different samples using a Minolta Chroma Meter fitted with CR-300 measuring head (Minolta, Osaka, Japan). Measurements of the instrument were standardized with respect to a white calibration plate, every time before use. The CIE (Commission Internationale de l’Eclairage), L*, a*, b*, colorimetry system was used for color determination with L* representing lightness, a* representing redness and b* representing yellowness. All of the measurements were collected from areas on the ham surface without visual excess fat, and the values were recorded for C* (chroma) calculation using the following equation: C* = (a*² + b*²)^1/2. Values regarding control and OEOF samples (without essential oil), were common with those reported in our previous paper [52 (link)], while the results relevant to the essential oil supplemented films—OEOS (which is the purpose of this paper) are reported for first time in the current paper.

The fruit ripening was evaluated and monitored by periodic measurements of fruit respiration, firmness, and peel color. Fruit color was evaluated by manual observation and measurement with a colorimeter. Manual observations were evaluated by the fruit ripening index, which is a scale from 1 to 6 as described by Omar et al. (2012) (link) with minor modifications: (1) Bright green in color, green-mature; (2) green with a small amount of yellowish color; (3) more green than yellow; (4) more yellow than green; (5) Yellow with a small amount of green; and (6) Completely yellow. The fruit color was also determined using a chromameter-2 reflectance colorimeter (Minolta, Osaka, Japan) equipped with a CR-300 measuring head and recorded as lightness (L), hue angle (h), or chroma (c). Five points around the equatorial region on each fruit were selected for the measurement. The fruit firmness was determined using an Instron 5,542 penetrometer (Instron, Norwood, MA, United States) equipped with a cylindrical flat-surfaced plunger (5 mm diameter). A 2-mm slice of fruit skin was removed, and the firmness of fruit was measured at a penetration depth of 2 cm on three different fruit at five different points per fruit. Fruit firmness (N) was expressed as the mean of these 50 measurements. Fruit respiration was determined using gas chromatograph as described by Zhu X. et al. (2015) (link).