Ohmic heating inactivation of Clostridium sporogenes in green bean puree and its effect on sensory attributes

Conventional thermal processing of heat-sensitive low-acid foods like green bean puree ensures microbial safety but often compromises sensory quality. Ohmic heating (OH) offers a promising alternative by rapid and uniform heating as well as accelerated spore inactivation. This study evaluated the effectiveness of OH in inactivating Clostridium sporogenes PA3679 spores, a surrogate for C. botulinum , in green bean puree (GBP) and assessed its effects on sensory attributes. Spore inactivation kinetics were compared between OH and conventional heating (CH) in capillary tubes at 110, 120, and 130°C at various electric field strengths and frequencies. OH demonstrated significantly greater lethality than CH, with a 4.04 log CFU/ml reduction at 130°C compared to 0.88 log by CH. We also conducted scaled-up inactivation trials on GBP using specially fabricated electrode-embedded pouches compared to conventionally retorted GBP at a similar process temperature and kill level of C. sporogenes . Temperature distribution in the pouch during OH was modeled and verified experimentally. Sensory evaluations, including trained descriptive and consumer acceptance panels, were conducted to assess the appearance and aroma of raw, OH-treated, and conventionally retorted purees. In pouch experiments, OH (30 V/cm and 5 kHz) achieved sterility in 2 minutes, while CH required 3 minutes and 42 seconds at 121.1 o C. Sensory analysis showed that OH-treated (30 V/cm and 5 kHz) puree retained significantly more green color and fresh aroma. Consumers also rated its color as more acceptable and preferred it over the retorted sample. These findings support the potential of OH to enhance both microbial safety and sensory quality in low-acid food processing. • Greater spore inactivation was achieved by ohmic heating (OH) at all temperatures • OH achieved faster sterilization of C. sporogenes (2 min) than retort (3.7 min). • OH preserved green color and fresh aroma significantly better than retort processing. • Consumers prefer sensory attributes of ohmic treated puree over retort processed.