A technique for the approximate quantitative prediction of flat souring in canned peas

Abstract

It is shown that the percentage of canned peas that will sour on incubation a t 1 3 1 '~ ( 5 5 . 0 '~) may be predicted approximately by enumerating the flat-sour spores in unprocessed cans, expressing the cannery process in terms of decimal reduction times for flat-sour spores, calculating the number of surviving spores per can and from this the percentage spoilage. Graphs have been drawn to simplify the expression of processing times as decimal reduction times, and for calculating the percentage spoilage from the number of surviving spores per can.A technique for the survey of pea-canning lines is described.In the Union of South Africa, the Regulations of the Department of Agriculture provide for the incubation at 131' F (55.0" c) of samples from each day's production of canned vegetables intended for export ; if souring (or gas production) is found in more than 26y0 of the samples incubated at this temperature, the export of the product is prohibited. In S. Africa flat-sour spores of high average heat-resistance are found in large numbers on vined peas, and in-plant multiplication is seldom the primary cause of flat-sour spoilage. The existence of this Regulation therefore imposes a difficult task on canners, and has created a need for a technique that will not only detect the presence of ' flat-sour ' organisms in the canning plant, but give an indication of the final percentage spoilage that would result from a given level of contamination. Incubation of processed cans for 5-10 days is too slow, since, by the time the presence of flat-sour organisms is detected in this way, and the results of the appropriate remedial measures are known, the production from at least two full working weeks will already have been packed ; moreover, if the initial attempts to reduce contamination are found to have been unsuccessful, nearly half the pea-canning season may be over before the results of any further changes are known.Few detailed descriptions of techniques for the bacteriological survey of vegetable-canning plants appear to have been published, but, during a visit to Washington in 1947, Dr. Yesair, of the National Canners' Association, kindly supplied the author with details of the method used there ; these methods formed the starting point for the work described in this paper and they provide a valuable guide to the general bacteriological condition of the canning plant. However, they are not designed to provide data from which the percentage of souring could be predicted in processed cans. Johnson et al.1 drew attention to the fact that the number of flat-sour spores needed to sour a can of peas was very small, and that it was quite possible that the plating of a few millilitres of the washings from the peas in an unprocessed-line can would fail to detect the presence of small numbers of spores. The authors employed a flask test in which 100 g. of peas covered with brine was processed for 35 minutes at 240' F (I'i5.5" c), incubated at 131' F (55.0" c) and tested for acid production daily for 5 days. By this method...

The temperature dependence of the lethal rate in sterilization calculations

“…T A = 100°C in the calculations for Table 2. The choice of T A is arbitrary, but it can be shown that any value of ir, in the range 100-140°C results in a similar value of the ratio (tRl/tR2)1000 f Levine (1956), (b) Deindoerfer (1957), (c) Klostergaard (1965), (d) Ball & Olsen (1957), (e) Stumbo, Murphy & Cochran (1950), (f) Knock (1954). …”