Identification of Cold Spots Using Non-Destructive Hyperspectral Imaging Technology in Model Food Processed by Coaxially Induced Microwave Pasteurization and Sterilization

Abstract

The model food in this study known as mashed potato consisted of ribose (1.0%) and lysine (0.5%) to induce browning via Maillard reaction products. Mashed potato was processed by Coaxially Induced Microwave Pasteurization and Sterilization (CiMPAS) regime to generate an F0 of 6–8 min and analysis of the post-processed food was done in two ways, which included by measuring the color changes and using hyperspectral data acquisition. For visualizing the spectra of each tray in comparison with the control sample (raw mashed-potato), the mean spectrum (i.e., mean of region of interest) of each tray, as well as the control sample, was extracted and then fed to the fitted principal component analysis model and the results coincided with those post hoc analysis of the average reflectance values. Despite the presence of a visual difference in browning, the Lightness (L) values were not significantly (p < 0.05) different to detect a cold spot among a range of 12 processed samples. At the same time, hyperspectral imaging could identify the colder trays among the 12 samples from one batch of microwave sterilization.

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“…Mashed potato (food model) was prepared as previously reported by Soni et al [ 8 ]. In short, to prepare 1000 g of mashed potato (food model), agar (Fort Richards, Auckland, New Zealand) (5 g) was added to boiling water (830 g) and mixed using a cake mixer at medium speed for 2 min followed by addition of potato flakes (150 g) while mixing continuously to avoid lumps.…”

“…The mix was cooled to 60 °C, followed by addition of D-ribose (10 g) and lysine (5 g) and mixed for another 2 min. Ribose and lysine (1 and 0.5%, respectively) have been reported to show formation of brown color with increasing time in the presence of heat, which can be measured by colorimetry [ 8 , 19 ]. This final composition of food model was left to cool in the room temperature for 10 min and then filled into packaging trays (174 × 103 × 35 mm) to reach a total weight of 250 g, while excluding the weight of the tray (20 g).…”

“…CiMPAS system (Coaxially induced microwave-pasteurization and -sterilization) as previously described by Soni et al [ 8 ] was manufactured by Meyer Burger Germany GmbH (Hohenstein-Ernstthal, Germany) and the industrial microwave parts were manufactured by MUEGGE GmbH (Reichelsheim, Germany). CiMPAS equipment used in the current study consists of a hot water tank, a warm water tank a process vessel (with microwave outlets) and an electric cabinet.…”

“…After processing using CiMPAS, each tray was divided into nine different locations on the surface as previously described [ 8 ]. The lightness (* L values) were recorded using a Minolta CR20 colorimeter (Minolta Camera Co., Osaka, Japan) and using *Lab (CIELAB) space as previously reported [ 19 , 20 ].…”

“…The lightness (* L values) were recorded using a Minolta CR20 colorimeter (Minolta Camera Co., Osaka, Japan) and using *Lab (CIELAB) space as previously reported [ 19 , 20 ]. The coldest spot on each tray was identified as the location with the significantly highest L values ( p < 0.05) as the L -values reduce significantly as an effect of the increase in time when subjected to thermal treatment [ 8 ]. The increase in the brown color formation and hence the decrease in * L values has been previously validated using a kinetic study using oil bath set up at 121 °C [ 8 ].…”