Effects of Gamma Irradiation at ‐78°C on Microbial Populations in Dairy Products

Abstract

The effect of low temperature ( -78°C) gamma irradiation was investigated on microbial populations in selected dairy products to determine the irradiation dosage needed to produce commercially sterile dairy products for immunosuppressed patients. 40 kGy irradiation was sufficient to sterilize ice cream and frozen yogurt, but not mozzarella or Cheddar cheeses. Up to 8 wk continued incubation of the 40 kGy irradiated products at 7°C or 35°C resulted in no resuscitative growth in ice cream or yogurt, but identifiable growth in the cheeses. The 12D for B. cereus preinoculated into cheese and ice cream was 43-50 kGy.

Destruction of Bacillus anthracis strain Sterne 34F2 spores in postal envelopes by exposure to electron beam irradiation

“…(1990) reported D 10 values from 3·6 to 4·1 kGy at −78°C in dairy products. These D 10 values are similar to those found in this study, although those reported by Hashisaka et al. 1990 were determined at −78°C.…”

“…Following this same rationale, a radiation dose comparable with a thermal process for canned foods would be 40 kGy using the data from this report, 45 kGy for the Bowen et al. (1996) data, and 49·2 kGy for the highest value reported by Hashisaka et al. (1990).…”

“…While there is little data available on the radiation resistance of B. anthracis , there is additional data on a closely related species, B. cereus . Briggs (1966) reported a D 10 value for B. cereus of 1·6 kGy in distilled water at ambient temperature, while Hashisaka et al. (1990) reported D 10 values from 3·6 to 4·1 kGy at −78°C in dairy products.…”

Protezione degli alimenti mediante radiazioni e radioresistenza dei microrganismi

“…40 kGy sono stati sufficienti per la radappertizzazione del gelato e dello yogurt gelato, ma non per la mozzarella e per il formaggio cheddar 30 . 40 kGy sono stati sufficienti per la radappertizzazione del gelato e dello yogurt gelato, ma non per la mozzarella e per il formaggio cheddar 30 .…”

Effect of gamma radiation on lipids by the TBARS and NMR

“…Due to the characteristics of composition, that is, a high quantity of water and the presence of saturated and unsaturated fats, milk and its derivatives are sensitive to oxidative rancidness after radiation treatment, which in many cases makes the products unacceptable for the consumption because of the presence of unwanted flavor. For this reason, studies using radiation on fluid milk and dairy products have been seldom done, in spite of work having been done in recent decades to examine the efficiency of radiation on the reduction of microorganisms which contaminate and deteriorate fluid milk (Naghmoush et al, 1983;Rosenthal et al, 1983;Schoonmaker, 2001;Searle and Mcathey, 1989), on the chemical-physical and sensory characteristics of irradiated milk (Ciesla, et al, 2004;Guimarães et al, 2005) and on its effects on milk derivatives (Gurgel, 2000;Hashisaka et al, 1990;Pietranera et al, 2003;Silva, 2003). There are at present several methods for detection of rancidity in foodstuffs.…”