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Coliforms in processed mango: significance and control
R E O'Connor-Shaw1, J A Guthrie, K J Dunlop
1Queensland Department of Primary Industries, IFIQ, Hamilton, Australia.
Abstract:
The aims of this investigation were to enumerate coliforms in fresh mangoes, puree, cheeks, and cheeks-in-puree in order to determine the source of these organisms in the processed products, to determine methods for their control, and to identify coliforms isolated from cheeks-in-puree to determine whether they have any public health significance. Product from four processors was tested on two occasions. The retail packs of cheeks-in-puree having the highest coliform counts were those in which raw puree was added to the cheeks. Coliform counts in these samples ranged between 1.4 x 10(3) and 5.4 x 10(4) cfu/g. Pasteurisation reduced the coliform count of raw puree to < 5 cfu/g. Forty-seven percent of the 73 colonies, isolated as coliforms on the basis of their colony morphology on violet red bile agar, were identified as Klebsiella pneumoniae using the ATB 32E Identification System. Klebsiella strains were tested for growth at 10 degrees C, faecal coliform response, and fermentation of D-melizitose, to differentiate the three phenotypically similar strains, K. pneumoniae, K. terrigena and K planticola. Results indicated that 41% of K. pneumoniae isolates gave reactions typical of K. pneumoniae. A further 44% of strains gave an atypical reaction pattern for these tests and were designed 'psychrotrophic' K. pneumoniae. Klebsiella pneumoniae counts of between 2.1 x 10(3) and 4.9 x 10(4) cfu/g were predicted to occur in the retail packs of mango cheeks-in-puree produced by the processors who constituted this product with raw puree. In view of the opportunistic pathogenic nature of K. pneumoniae, its presence in these products is considered undesirable and steps, such as pasteurisation of puree, should be taken in order to inactivate it.
Insights
Raw puree addition significantly increases coliform counts in mango products. Pasteurization effectively reduces these bacteria, with Klebsiella pneumoniae identified as a key concern requiring control measures.
Area of Science:
- Food Microbiology
- Food Safety
- Microbial Contamination
Background:
- Coliforms are indicators of microbial contamination in food products.
- Understanding the source and control of coliforms in processed mangoes is crucial for public health.
Purpose of the Study:
- To enumerate coliforms in fresh mangoes, puree, and processed products.
- To identify the source of coliform contamination in processed mangoes.
- To determine effective control methods and assess the public health significance of isolated coliforms.
Main Methods:
- Enumeration of coliforms in various mango matrices (fresh, puree, cheeks-in-puree).
- Isolation and identification of coliforms using the ATB 32E Identification System.
- Testing Klebsiella strains for growth characteristics and fermentation patterns.
Main Results:
- Highest coliform counts were found in mango cheeks-in-puree made with raw puree.
- Pasteurization reduced coliform counts in raw puree to below 5 cfu/g.
- Klebsiella pneumoniae was identified as a significant coliform, with some strains exhibiting psychrotrophic properties.
Conclusions:
- Raw puree is a primary source of coliform contamination in processed mangoes.
- Pasteurization is an effective method to control coliforms, including Klebsiella pneumoniae.
- The presence of Klebsiella pneumoniae in mango products is a public health concern, necessitating control measures.