Determining effects of temperature abuse timing on shelf life of RTE baby spinach through microbial growth models and its correlation with sensory quality

Authors: Zhou, Bin; Luo, Yaguang - Sunny; HUANG, LIHAN - Oak Ridge Institute For Science And Education (ORISE); Fonseca, Jorge; YAN, HAIJUAN - Jiangsu University; HUANG, JINGWEI - Jiangsu University

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2022
Publication Date: 3/1/2022
Citation: Zhou, B., Luo, Y., Huang, L., Fonseca, J.M., Yan, H., Huang, J. 2022. Determining effects of temperature abuse timing on shelf life of RTE baby spinach through microbial growth models and its correlation with sensory quality. Postharvest Biology and Technology. 133. Article 108639. https://doi.org/10.1016/j.foodcont.2021.108639.
DOI: https://doi.org/10.1016/j.foodcont.2021.108639

Interpretive Summary: Interpretive Summary: Packaged ready-to-eat (RTE) baby spinach is a high-nutrient vegetable commonly consumed fresh. It is however, highly sensitive to physiological deterioration, especially under temperature abuse across all post-processing practices. Cold chain management during postharvest handling is of paramount importance to ensure its quality and shelf life. Thus, this study was conducted to evaluate the effect of early and late temperature abuse on microbial growth and on quality attributes of RTE baby spinach. In this study, following 2 days of commercial operations, including processing and distribution, and one day storage at 1 °C in research facilities, bagged baby spinach was transferred to refrigerated rooms at 4, 8, 12, 16, and 20 °C (early temperature abuse). A second group of spinach was transferred to the same sub-optimal temperatures after 7 days (late temperature abuse). Results indicated that all microorganisms including aerobic mesophilic bacteria, psychrotrophic bacteria, and yeast and molds, grew slowly when held consistently at 4 °C, while storage at 8 °C and above significantly accelerated the growth of these indigenous microorganisms. The effect of temperature abuse on microbial growth was described by a no-lag phase model or a suboptimal Huang square-foot model. Indigenous microbial populations highly (inversely) correlated with sensory attributes, and were associated with overall quality deterioration in RTE baby spinach. These results underline the importance of cold chain maintenance during the distribution of RTE baby spinach, and help industries make science-based decisions on product handling.

Technical Abstract: Maintaining an optimal cold chain during postharvest handling is of paramount importance to ensure quality and shelf life of ready-to-eat (RTE) fresh-cut produce. However, breaks along the cold chain tend to occur. This study evaluated the effect of temperature abuse encountered i) immediately after processing and ii) in the late stage of the shelf life on microbial growth and on related quality attributes of RTE baby spinach. Following 2 days of commercial operations, including processing and distribution, and one day storage at 1 °C in research facilities, bagged baby spinach was transferred to refrigerated rooms maintained at 4, 8, 12, 16, and 20 °C (early temperature abuse). A second group of spinach was transferred to the same sub-optimal temperatures after 7 days (late temperature abuse). Results indicated that all microorganisms, as indicated by total aerobic counts, psychrotrophic bacterial counts, and yeast and molds, grew slowly when held consistently at 4 °C, while storage at 8 °C and above significantly accelerated the growth of these indigenous microorganisms. The effect of temperature abuse on microbial growth was described by a no-lag phase model or a suboptimal Huang square-foot model. Indigenous microbial populations were highly associated with sensory attributes, with a negative correlation between APC and overall quality. This study underlines the importance of cold chain maintenance during the distribution of RTE baby spinach, and help industries make science-based decisions on product handling, particularly in predicting microbial growth based on temperature history.