Research – Evaluation of Listeria monocytogenes and Staphylococcus aureus survival and growth during cooling of hams cured with natural-source nitrite

Journal of Food Protection

Growing consumer desires for clean label, “natural” products drives more meat processors to cure meat products with natural sources of nitrate or nitrite such as celery juice powder (CJP). One particular challenge for these producers is to identify safe cooling rates in CJP-cured products where extended cooling could allow growth of pathogens. USDA FSIS recently added guidelines for stabilization of meat products cured using naturally occurring nitrites, based on control of Clostridium spp . Currently a gap exists in knowledge associated with safe cooling rates of naturally cured ham that prevent the growth of Listeria monocytogenes and Staphylococcus aureus that are potential post-lethality contaminants. The study aims to investigate the temperature profiles of naturally cured hams of typical sizes during refrigerator cooling and determine the survival behavior of S. aureus and L. monocytogenes on ham during these cooling periods. Whole (14 lbs / 6300 g), half (6 lbs / 2700 g) and quarter hams (3 lbs / 1400 g) were slowly cooked in Alkar Ò 1000 smokehouse until internal temperatures reached a minimum of 140 ° F / 60°C and were immediately transferred into walk-in cooler (38 ° F / 3.3°C). Cooling times for all sizes were within the requirements for cured products but not for uncured products. Worst-case scenarios of post-processing surface contamination were simulated by inoculating small, naturally cured ham samples with S. aureus or L. monocytogenes , which were cooled in controlled processes (130-45 ° F / 54.4-7.2 ° C in 720-900 min). B y the end of cooling, each inoculum had a small decrease of 0.5-0.6 log CFU/g. This study helps small processors identify if recommended concentrations of natural cure agents that prevent growth of Clostridium pathogens may also prevent growth of other pathogens during cooling, which aids small meat processors in production and quality control.

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