Is slimy ham safe to eat? (Spoilage signs)
In this brief guide, we will answer the question “Is slimy ham safe to eat?”, and will discuss how ham spoils and the shelf life of ham.
Is slimy ham safe to eat?
No, slimy ham should not be consumed. The development of a slimy texture is an early sign of spoilage due to bacterial contamination, often occurring before the product’s sell-by date.
Eating spoiled ham can result in foodborne illness, with ham being a common source of staphylococcal food poisoning. Common indicators of spoilage in cooked meat products include sensory defects such as ropy slime, a sour off-flavor, discoloration, excessive liquid, and gas production. (1, 2)
What are the reasons for sliminess in ham?
The presence of slime and other signs of spoilage in ham can be attributed to microbial growth. Some strains of lactic acid bacteria have been identified as specific spoilage organisms and are the primary culprits behind spoilage in vacuum and modified atmosphere–packed hams.
Ropy slime-producing lactic acid bacteria (LAB) are capable of thriving and surviving at refrigeration temperatures, competing with other bacteria in the ham. The sliminess is the result of the production of long-chain, high molecular mass, viscosifying, or gelling exocellular polysaccharides.
Consequently, even though refrigeration storage extends the shelf life of these products, it may not entirely prevent the formation of ropy slime. This continuous bacterial growth is facilitated by the development of slime, which acts as a protective barrier against external competitors. (3)
Why does ham spoil?
Sliced cooked ham is highly perishable. Distinct microorganisms can prevail in specific microenvironments within ham products, leading to unique issues and defects, influenced by the product’s composition, processing methods, and storage conditions.
Ham offers an ideal environment for microbial proliferation, thanks to its abundant supply of nutrients like glucose, proteins, amino acids, nucleotides, and lipids. Therefore, the availability of nutrients is not a limiting factor for their growth.
Ham’s low salt content (typically 2%-3.5% in the water phase), a pH level of approximately 6.0, and a water activity exceeding 0.945 create conditions that are conducive to the growth of various microorganisms, particularly Staphylococcus, which thrive in the relatively low-salt environment of pre-cooked, packaged hams. (1, 4, 5)
What are the risks of spoiled ham?
Consuming expired ham can result in food poisoning. This condition typically manifests through gastrointestinal symptoms like diarrhea, abdominal pain, and vomiting. In some cases, additional symptoms affecting neurological or systemic functions may arise.
The intensity of these symptoms can range from being asymptomatic or experiencing mild discomfort that doesn’t require medical attention to severe cases. Staphylococcal food poisoning presents with sudden symptoms including nausea, vomiting, and stomach cramps, often accompanied by diarrhea.
These manifestations typically occur within a time frame ranging from 30 minutes to 8 hours after consuming spoiled ham contaminated with Staph toxin and usually subside within 24 hours. Severe illness resulting from Staph food poisoning is uncommon. (6, 7)
How to store ham?
Cooked ham should be consumed promptly or refrigerated immediately at temperatures below 41°F (5°C). To ensure fast cooling, it is advisable to store the ham in smaller portions placed in shallow containers. These containers should have loose covers, allowing proper air circulation and facilitating efficient heat transfer from the ham to the container.
Before it is opened, sliced vacuum-packed cooked ham, which undergoes processing at temperatures ranging from 72 to 85 °C, can be stored for up to 30 days when kept at a temperature of 40°F (4°C).
For optimal quality, individuals also have the choice of freezing ham for a duration of one to two months. It is essential to understand that frozen ham remains safe indefinitely when stored at 0°F (-18°C). However, it is worth noting that in warmer conditions, signs of spoilage may become noticeable within a relatively short span of 3 to 5 days. (1, 2)
How to minimize the risk of foodborne illness?
To minimize the risk of contamination by staphylococcal gastroenteritis and other foodborne illnesses, proper preparation and serving of baked ham are essential.
Food contact surfaces and equipment, such as slicers, should be regularly cleaned and sanitized. Manual handling should be kept to a minimum. Ham should be sliced when cold or, if served warm, just before serving to reduce the chances of bacterial replication from slicing. (1, 2)
In this brief guide, we answered the question “Is slimy ham safe to eat?”, and discussed how ham spoils and the shelf life of ham. Studying this topic I was able to conclude that slimy ham is not safe to eat and should be promptly discarded as the formation of ropy slime is an early indication of spoilage that can lead to food poisoning in case of consumption.
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HU, Ping et al. Characterization of the predominant spoilage bacteria in sliced vacuum-packed cooked ham based on 16S rDNA-DGGE. Food Control, v. 20, n. 2, p. 99-104, 2009.
CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC et al. Outbreak of staphylococcal food poisoning associated with precooked ham–Florida, 1997. MMWR. Morbidity and mortality weekly report, v. 46, n. 50, p. 1189-1191, 1997.
CENCI-GOGA, Beniamino T. et al. Characterization and Growth under Different Storage Temperatures of Ropy Slime–Producing Leuconostoc mesenteroides Isolated from Cooked Meat Products. Journal of Food Protection, v. 83, n. 6, p. 1043-1049, 2020.
BORCH, Elisabeth; KANT-MUERMANS, Marie-Louise; BLIXT, Ylva. Bacterial spoilage of meat and cured meat products. International journal of food microbiology, v. 33, n. 1, p. 103-120, 1996.
MOSCHOPOULOU, E. et al. Food quality changes during shelf life. In: Food quality and shelf life. Academic Press, 2019. p. 1-31.
C. Rius Gibert, Food Poisoning: Epidemiology, Encyclopedia of Food and Health, Academic Press, Pages 67-71, 2016.
Centers for Disease Control and Prevention [CDC]. Staphylococcal (Staph) Food Poisoning. 2023.