The effect of substrate on the radiation resistance of yeasts isolated from sausage meat

Abstract

The radiation resistance of a selection of yeasts isolated from sausages was assessed in phosphate-buffered saline and in sausage meat. The yeasts Candida zeylanoides, Debaryomyces hansenii and Trichosporon cutaneum exhibited sigmoidal survival curves in both substrates whilst the more sensitive Sporobolomyces roseus exhibited an exponential survival curve in buffer but a sigmoidal curve in meat. Irradiating C. zeylanoides, D. hansenii and T. cutaneum in sausage meat changed the shape of their survival curves to significantly alter the calculated parameters Ds (the dose in kGy that must be achieved before reduction in numbers occurs) and D10sig (the dose in kGy required after the shoulder to achieve a 1 log cycle reduction in numbers). The Ds values were reduced while higher D10sig values were obtained demonstrating that the sausage meat contributed a protective effect to these yeasts at higher irradiation doses. For the yeast S. roseus, similar numbers of survivors were recovered from both substrates at initial low irradiation doses (0-0.5 kGy) with the protective effect being demonstrated again at higher doses (> 2 kGy). These findings should be considered when defining a commercial process to reduce the numbers of yeasts in these products.

Inactivation of Enterobacter sakazakii in Infant Milk Formula by Gamma Irradiation: Determination of D10‐Value

“…These results can be explained by the protective effect of protein, fat, and carbohydrate in the RIMF. The composition of suspending menstruum in which the microorganism was exposed to ionizing radiation greatly affects the sensitivity of the microorganism to ionization radiation (McCarthy and Damoglou 1996; Jay 2000; Mayer‐Miebach 2005; Farkas 2006). McCarthy and Damoglou (1996) reported that the D 10 ‐value is dependent on suspending menstruum and increases with complexity (for example, protein, fat, or carbohydrate) of the food system.…”

“…The composition of suspending menstruum in which the microorganism was exposed to ionizing radiation greatly affects the sensitivity of the microorganism to ionization radiation (McCarthy and Damoglou 1996; Jay 2000; Mayer‐Miebach 2005; Farkas 2006). McCarthy and Damoglou (1996) reported that the D 10 ‐value is dependent on suspending menstruum and increases with complexity (for example, protein, fat, or carbohydrate) of the food system. Patterson (1989) and Urbain (1986) explained the protective effect of food components to the competition between food components and microorganisms in food system for interaction with oxidative radicals formed during irradiation, thus reducing the effect of the radiation damage and making the organisms more resistant to ionizing radiation.…”

Current progress of emerging technologies in human and animals’ milk processing: Retention of immune‐active components and microbial safety

“…Direct irradiation should be more effective than indirect irradiation; however, milk and infant formula are complex systems with protein, fat, and carbohydrate. It has been reported that compositional complexity may reduce the radiation damage to microorganisms by interaction with generated oxidative radicals during irradiation (McCarthy & Damoglou, 1996). Moreover, water activity ( a w ) plays an important role in radiation damage, as a low a w may reduce the generation of free radicals, reducing the indirect irradiation damage to the nucleic acid of micro‐organisms.…”