![]() The presence of seam defects increases the chance of this contamination occurring particularly whilst the cans are wet. Only when cans are cool and dry is this risk eliminated. The length of satisfactory storage time depends on the nature of the product inside the can, the specification of the can used, and the external conditions to which the can is exposed.Ĭans are highly susceptible to external bacterial contamination immediately after the heat process, when cans are still wet, even when a good seam has been formed. The implications of damage and rusting to the safety of the product is a matter for the expert judgement of a canning technologist, and such advice should be sought if there is any doubt. Rusty body plate below a label which shows no corresponding rust staining usually suggests that the cans were rusty when labeled. Rusting may be light surface rust through to highly localized and deep seated pitting. ![]() ![]() Rusting of cans may be caused by wetting with fresh or salt water, condensation due to rapid changes in ambient temperature, from the glue used to apply labels or from high levels of sulphate or chloride in the label or case packing material. ![]() Additionally, physical damage may result in external rusting due to damage to the surface coating or internal corrosion by aggressive contents on areas damaged internally by the external impact. Expert examination of the cans and contents, preferably those which have not ‘blown’ but are showing signs of spoilage such as swelling, will usually enable the problem to be accurately diagnosed.Įxternal physical damage to cans may result in loss of can integrity, with potential contamination resulting, even though no visible leakage, hole or aperture exists. with pH’s below 4,5 will spoil but not present a serious food poisoning risk. High acid foods such as canned fruit, tomatoes, tomato puree etc. Bacterial spoilage of low acid foods (pH 4,5 or above), e.g. The type of spoilage and its significance to public health will depend to a large extent upon PH (degree of acidity). Such associated damage should also be reported. Ultimately the cans may explode and surface contaminate, damage and consequently corrode other cans in the vicinity. The distension will vary from a reversal of the concavity of the ends (which may be pressed back with the thumb) to heavily swollen cans with permanently distended ends and a reversal of the countersink area. heating, cooling and drying) to ensure that all bacteria or micro-organisms which would otherwise cause spoilage, are destroyed or denied access.īacterial spoilage may manifest itself by the distension (blown cans) caused by gases formed by the bacterial action, although surveyors should be aware that spoilage can occur without gas formation, depending on the organism involved. The cans must be adequately processed, which requires careful control of the thermal process (i.e.Unless an hermetic seal is achieved, spoilage, after short periods of storage, will result in the majority of cases. The cans must be hermetically sealed which requires the can components to be sound, correctly assembled and properly seamed together.Cans cannot be stored indefinitely some products have comparatively short shelf lives.ĭuring the manufacture of canned product many extracting criteria must be met but two in particular are fundamental to the achievement of shelf stability. Properly prepared canned products will remain stable and safe to eat over long periods provided that they are stored and handled correctly.
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