Effect of hot-fill processing at reduced temperatures on tomato sauce microbiological stability in plastic packaging

Abstract

Tomato sauce production technology implies cooking at 80-95 ºC. High-density polyethylene (HDPE) packaging material is not recommended for hot-fill process, mainly because of packaging deformation under the influence of high temperature. However, condiments could be cooled and then filled in a HDPE bottle, but the secondary contamination still can occur during the filling process. The aim of the study was to find out whether cooked tomato sauce can be filled in HDPE bottles at reduced temperatures. Two commercial products were hot-filled at 65, 70 and 75 ºC, and incubated at 30 ºC for 12 weeks for accelerated shelf life prediction, assuming the temperature coefficient (Q10) is 2. Microbiological tests were performed after each 2 weeks. Based on target bacteria kinetic factors obtained from literature, and time-temperature data obtained during the hot-fill process, theoretical evaluation of heat treatment processing effectiveness was performed, resulting in prediction that no bacterial growth should be observed during the sample incubation. Untreated samples showed 4 ± 0.2 log10 g-1 total plate count (TPC), 2.4 ± 0.2 log10 g-1 yeasts and moulds count, and various mesophilic lactic acid bacteria and sulphite-reducing bacteria count. After heat treatment, both samples showed stable TPC during the incubation at 30 ºC for 12 weeks, which allowed us to conclude, that expected shelf life of chosen commercial products is at least 6 months. Study result brings us in-depth knowledge about commercial product microflora heat resistance and behaviour during the accelerated shelf-life storage, as well as expands our understanding of industrial pasteurization process designing.