Der natürliche und erntebedingte Keimgehalt roher Speisekartoffeln sowie Verfahren zur Reduzierung der Keimbelastung während der Kartoffelverarbeitung vor dem Sterilisationsprozeß

Raw unpeeled potatoes of different variety and cultivation conditions were analyzed for their natural and harvest-caused bacterial load. By means of gradual control it was demonstrated, what size of count reduction could be achieved by technological processes like rinsing, peeling, blanching and predrying in the course of potato-processing. By means of artifical contamination of raw potatoes with Bacillus-spores it should be elucidated which type of food processing is suitable to reduce the bacterial load. Within a test period of 18 weeks the total microbial load of the potato peels amounted to about 10 high 8 colony forming units per g. The microbial count values of the cores of artifically contaminated potatoes were always higher than the counts of the naturally contaminated samples. At the end of the storage time in the cores of intact potatoes there could be enumerated equal or smaller than 100/g of bacteria and moulds. With the exception of artifically contaminated samples there w as no growth of moulds in the cores. The risk of microbial contaminations of potatoes is dependent on the rate of harvest-caused injuries. By gradual processing with rinsing, knife-peeling and blanching a total count reduction of 8 logcycles could be reformed. With steam-peeling, the heat-resistant Bacillus-spores were inactivated to a large extent. The residual microbial load of pretreated potatoes represents no problem for a subsequent sterilization process, provided that after these pretreatments a recontamination can be excluded