A comparative study of high pressure sterilisation and conventional thermal sterilisation: Quality effects in green beans

Abstract

Experiments were conducted to compare the colour, texture and microbiological quality of green beans that had been either high pressure sterilised (HPS) using commercially achievable pressures (a pre-heat to 86 °C followed by two treatments of 2 min at 700 MPa) or were conventionally thermally sterilised (Fo 1 to 3 min with a retort temperature of 115 °C). Samples were assessed immediately after processing and after 7 months of ambient storage. HPS treated samples were generally darker in appearance (L⁎ values shifted downwards) compared with heat treated (F0 3 min) samples. The a⁎ values for HPS samples were significantly (P 0.05). HPS treated samples were typically twice as firm as F0 3 min treated samples (P < 0.05). There was some softening over storage but this differential in firmness was maintained after 7 months. Total aerobic and anaerobic plate counts and spore counts after storage were below the limits of detection in all samples apart from one canned sample where leaker spoilage had occurred. Industrial relevance Thermal sterilisation technologies are used to produce ambient stable products but frequently these products suffer deleterious quality changes such as colour and texture modification as a result of processing. There is industrial interest in any technologies with the potential to produce ambient stable products with improved retention of ‘fresh’ characteristics. High pressure sterilisation is a promising method for the production of ambient stable products with improved quality.