Fecal streptococci in frozen foods. IV. Effect of sanitizing agents and blanching temperatures on Streptococcus faecalis.

Low-temperature heat treatment for sanitizing fruits and some vegetables is very detrimental to the appearance of the products. Fruits especially are so softened that they are extremely difficult to market. In order to correct this trouble, industries use such chemical sanitizing agents as chlorine and the quaternary ammonium compounds in the processing of many fruits. All these chemicals are inactivated by the organic materials that make up the physical composition of the fruit or vegetable. This phenomenon could be a serious problem if complete elimination of organisms is desired. Investigations by Rudolfs, Falk, and Ragotzkie (1951a, b, c) showed that, if sewage irrigation or night soil application was stopped one month before the tomato harvest, the fruit could be safely consumed raw. The possibility that the tomatoes would be vectors for the transmission of enteric diseases was considered unlikely. Later studies on decontamination of tomatoes showed that storage, or washing with or without detergents, was ineffective. Germicidal rinses containing chlorine were superior to the other methods, but were unreliable. The only effective method of decontamination was pasteurization at 60 C for five minutes. Pederson (1947) studied the processing of vegetables before freezing and found that a large proportion of the bacteria are destroyed by the blanching process. However, the surviving bacteria may develop during cooling, handling, and prefreezing. Under commercial conditions, some contamination of the food by bacteria was caused by vegetable juices spilling on the processing equipment, thus providing medium for growth. Bacterial counts, therefore, should be considered as an indication of the care with which vegetables are handled between blanching and freezing. It was noted also that no coliform bacteria or enterococci were found on vegetables directly after blanching. From the results of the frozen food survey of Larkin, Litsky and Fuller (1955), it can be seen that fecal streptococci were present in many of the commercial frozen foods. Where does this contamination occur?