2.1.2. MAPS and Frozen Meal Processing

MAPS Processing/Freezing: On the day following production, 60 trays of the daily production of 120 were processed through MAPS and the other half were frozen (−35 ◦C) and used as a control. In total, 180 were frozen as controls and 180 trays were pasteurized in a pilot-scale MAPS in the Food Processing Pilot Plant at Washington State University (WSU), Pullman, WA. A detailed description of MAPS can be found in Tang et al. (2018) [19]. The specific processing conditions used to produce jambalaya in the MAPS are described in the methods section of Montero et al., (2020) [22]. At the time the study was conducted, the MAPS could process 16 trays in one run; thus, there were 12 total runs. After being MAPSprocessed, the 180 trays were stored at 2.0 ± 0.5 ◦C. A Temperature Data Logger RC-5+ (Elitech, CA, USA) was used to track the storage temperature during the whole study.

A total of 180 trays were used as control samples (frozen and stored at −31 ◦C). The control samples were sealed under conditions identical to those of the MAPS-samples. During the freezing step, the sample trays were placed on boards across the top shelves in a freezer 1 m in front of the evaporator with an air velocity of 1.6 m/s and stored at −31 ◦C. The storage conditions for the control samples were selected to ensure minimal product changes over the length of the study.

Trays of each type (MAPS and control) were randomly selected and analyzed for microbial, sensory, and chemical properties at 2, 8, and 12 weeks of storage.

Microbial/Safety Testing: At weeks 2, 8 and 12 microbial analyses were performed. MAPS-processed jambalaya and control trays were randomly selected and sent to Microchem Laboratories (Seattle, WA, USA). The jambalaya samples were screened for the following pathogens as a way to assure their safety before human consumption, *Bacillus cereus* (Local Instruction); *Salmonella*; *Listeria monocytogenes*; and *E*. *coli* O157:H7 (AOAC 050501). For the analyses of pathogens, a 25 g sample was tested. The following analyses from AOAC International Official Methods of Analysis were used to detect signs of spoilage: aerobic plate count; yeasts and molds; and total coliforms. The results from the microbial testing are presented in Table 3.

Based on the microbial testing results the jambalaya meals were safe for consumption at each of the evaluated time points.

The jambalaya meals were evaluated in two separate sensory evaluations by two different groups of participants, a home-use test and a semi-trained panel evaluation.


**Table 3.** Pathogens and spoilage-related microbial analyses conducted on the MAPS-processed jambalaya and the control during 12 weeks of storage at 2 ◦C and −31 ◦C, respectively.

<sup>1</sup> Microwave-thermally processed jambalaya is represented as MAPS and cooked frozen jambalaya is represented as Control.
