Inactivation of non-proteolytic Clostridium botulinum type E in low-acid foods and phosphate buffer by heat and pressure

Abstract

The effect of high pressure thermal (HPT) treatments on the inactivation of spores of non-proteolytic type E Clostridium botulinum TMW 2.990 was investigated at high pressures (300 to 600 MPa) and elevated temperatures (80 to 100 °C) in four low-acid foods (steamed sole, green peas with ham, vegetable soup, braised veal) and imidazole phosphate buffer (IPB). In addition, corresponding conventional thermal treatments at ambient pressure were performed to expose possible synergisms of pressure and temperature on spore inactivation. In general, spore count reduction was more efficient by combining pressure and temperatures < 100 °C and the overall process duration could be shortened due to accelerated heating rates (adiabatic effect). Processing at 90 °C and 600 MPa resulted in inactivation below the detection limit after 5 min in all foods except steamed sole. Traditional thermal processing of spores at 90 °C for 10 min, on the other hand, did not result in an estimated 6-log reduction. Additional HPT treatments in steamed sole and IPB did not reveal pronounced food matrix dependent protective effects. Here, varying pressure levels did not appear to be the driving force for spore count reduction in steamed sole at any temperature. By applying a Weibull distribution on destruction kinetics of isobaric/isothermal holding times, 6D-values were calculated. Compression and decompression phase (1 s pressure holding time) had a considerable impact on spore count reduction (max. -2.9 log units) in both, foods and buffer. Hence, compression and decompression phases should directly be included into the total lethal effect of HPT treatments to avoid prolonged holding times and overprocessing.

Phage lysin that specifically eliminates Clostridium botulinum Group I cells

“…High-temperature processing in the food industry is the most effective method for inactivation of C. botulinum spores and the neurotoxin, but often compromises nutritional and sensory qualities of food products 4 . There is a growing interest in development of novel methods alternative to thermal process to control the botulism hazard 5 , 6 .…”

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

“…In recent studies with proteolytic (types B) and nonproteolytic (type E) C. botulinum strains in food model systems and different types of real foods, spore stabilization by HHP against high temperature inactivation could be confirmed, namely for type B strains. It was demonstrated for C. botulinum type B that, at a given temperature (100, 110, and 120 • C), spore inactivation was increased when pressure was reduced, for example, from 600 to 300 MPa (Maier et al, 2018). Such fundamental differences given, it is unlikely that true surrogates for Clostridium spores for the purpose of evaluating the effectiveness of HPT processes can be found within Bacillus species.…”

High‐pressure pasteurization of low‐acid chilled ready‐to‐eat food

“…Maier et al. (2018) have suggested that storage temperatures below 3°C can be considered (for low‐acid chilled storage products) as a safety limitation for chilled meals.…”

“…The results of these various studies emphasize the need for temperature control during storage for the microbial safety of low-acid pasteurized products. Maier et al (2018) have suggested that storage temperatures below 3 • C can be considered (for low-acid chilled storage products) as a safety limitation for chilled meals.…”