Growth and survival of L. innocua and TAC in artificially inoculated Turkish White Cheese during manufacturing and storage periods, with respect to different level of contamination of L. innocua were investigated.
Cheese products were manufactured by the short-set procedure in pilot-plant-sized vats, as in AOÇ / dairy factory. Pasteurized cow&rsquo / s milk was inoculated with L. innocua for obtaining the initial loads of 3.84 and 7.12 log CFU/ml. Bacterial load of inoculated milk, whey, post-ripened curd and post-salted cheese was determined during processing at 20± / 5º / C.
Cheeses were stored in 16% saline solution at 4 ± / 2º / C for up to 45 days. Samples were taken from each treatment and analysed on 5, 10, 15, 20, 30 and 45 days. Total decrease of L. innocua in Turkish White Cheese with each inoculum dose was approximately 2 logs during the storage period. L. innocua values were also compared with TAC values.
The results had shown that, if pasteurization is not as sufficient as to kill this bacteria in contaminated raw milk, or if there is post-process contamination, Listeria can survive during the manufacture and storage, although they decrease in number. Storage (ripening) period for consumption of cheeses should be at least 90 and 178 days, in low and high inoculum dose, respectively.
Physico-chemical properties of cheese as pH, acidity, salt, fat, moisture contents during storage period were determined. Salt concentration, pH value and storage temperature had a cumulative bactericidal effect on microorganisms.
In this respect, effect of implementing HACCP method on reducing the Listerial contamination of Turkish White Cheese was determined for checking the quality problems in a cheese plant and for directing the companies as a guide.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12605543/index.pdf |
| Date | 01 June 2004 |
| Creators | Ozturkoglu, Sebnem |
| Contributors | Gurakan, Candan |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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