Effect of oscillatory high hydrostatic pressure treatments on Byssochlamys nivea ascospores suspended in fruit juice concentrates

Abstract

and oscillatory (one, three or five cycles at 689 MPa with holding times of 1 s) high hydrostatic pressure treatments on the viability of Byssochlamys nivea ascospores suspended in apple and cranberry juice concentrates adjusted by dilution to water activities (a w ) of 0·98 and 0·94 was evaluated at 21 and 60°C. Inactivation of the initial spore inocula was achieved after three or five cycles of oscillatory pressurization at 60°C when the a w was 0·98 in both fruit juices. With a w 0·94, the initial inocula were reduced by less than 1 log-cycle after five pressure cycles. Inactivation was not observed within 25 min with continuous pressurization at 60°C. In treatments at 21°C, no effect on spore viability was observed with continuous or oscillatory treatments.

Destruction of Salmonella Enteriditis inoculated onto raw almonds by high hydrostatic pressure

“…The results of this study confirmed the results of other researchers (Palou et al, 1998;Hayert et al, 1996), showing that low a w imparts a protective effect on bacterial cells. This work also showed that HHP is much more effective at reducing the microbial load in foods with higher water activities.…”

“…For both strains of S. Enteriditis, the discontinuous process resulted in greater than a 1 log reduction in viable bacteria. These results are in agreement with the other studies (Hayakawa, Kanno, Yoshiyama, & Fujio, 1994;Palou et al, 1998), that showed that discontinuous processing is more effective than continuous processing at reducing bacterial concentrations. Nevertheless, it is clear that the low a w of the almonds limited the ability of the discontinuous process to greatly reduce the S. Enteriditis concentration, a result supported by other studies (Palou et al, 1998).…”

“…These results are in agreement with the other studies (Hayakawa, Kanno, Yoshiyama, & Fujio, 1994;Palou et al, 1998), that showed that discontinuous processing is more effective than continuous processing at reducing bacterial concentrations. Nevertheless, it is clear that the low a w of the almonds limited the ability of the discontinuous process to greatly reduce the S. Enteriditis concentration, a result supported by other studies (Palou et al, 1998). The manner in which pressure is applied during processing (continuously or discontinuously) has a significant effect on the bacterial inactivation achieved, and several studies have shown that discontinuous pressure processing can vastly increase bacterial inactivation as compared to continuous processing (Palou et al, 1998;Hayakawa et al, 1994).…”

“…Bacterial cells, yeasts and molds are relatively sensitive to pressurization below 100,000 psi, but bacterial spores can be quite resistant. Several variables, including magnitude of pressure, pressurization time and temperature, microbial types, cell growth phase, suspending media, and the presence of antimicrobial substances have been reported to influence the hydrostatic pressure induced death of microbial cells (Alpas et al, 1999;Benito, Ventoura, Casadei, Robinson, & Mackey, 1999;Kalchayanand, Ray, Sikes, & Dunne, 1998a; , 1998b;Patterson & Kilpatrick, 1998;Palou et al, 1998). Generally, microbial destruction will increase with increases in pressure, pressurization time and temperature, in suspending media with low solid content, and in the presence of antimicrobial properties (Alpas et al, 1999).…”

Inactivation ofSalmonellaEnteritidis in Chicken Breast Fillets by Single-Cycle and Multiple-Cycle High Pressure Treatments

“…Multiple-cycle HHP treatments have been reported by some authors to be more effective than single-cycle treatments for the destruction of bacterial and mold spores (Hayakawa et al, 1994;Palou et al, 1998), although variable results have been obtained for vegetative cells. In the case of Salmonella, multiple-cycle treatments of liquid whole egg at 350 or 450 MPa (Ponce et al, 1999) or at 138 MPa (Huang et al, 2006) were more lethal than single-cycle treatments.…”