Effect of Hurdle Approaches Using Conventional and Moderate Thermal Processing Technologies for Microbial Inactivation in Fruit and Vegetable Products

Abstract

Thermal processing of packaged fruit and vegetable products is targeted at eliminating microbial contaminants (related to spoilage or pathogenicity) and extending shelf life using microbial inactivation or/and by reducing enzymatic activity in the food. The conventional process of thermal processing involves sterilization (canning and retorting) and pasteurization. The parameters used to design the thermal processing regime depend on the time (minutes) required to eliminate a known population of bacteria in a given food matrix under specified conditions. However, due to the effect of thermal exposure on the sensitive nutrients such as vitamins or bioactive compounds present in fruits and vegetables, alternative technologies and their combinations are required to minimize nutrient loss. The novel moderate thermal regimes aim to eliminate bacterial contaminants while retaining nutritional quality. This review focuses on the "thermal" processing regimes for fruit and vegetable products, including conventional sterilization and pasteurization as well as mild to moderate thermal techniques such as pressure-assisted thermal sterilization (PATS), microwave-assisted thermal sterilization (MATS) and pulsed electric field (PEF) in combination with thermal treatment as a hurdle approach or a combined regime.

Keywords: D values; MATS; PATS; PEF; fruits; thermal; vegetables.

Figure 1

Diagram of a possible continuous PEF device used to treat food samples (adapted from Taha, et al. [64] (reprinted from Pulsed Electric Field: Fundamentals and Effects on the Structural and Techno-Functional Properties of Dairy and Plant Proteins. Taha, Ahmed, Casanova, Federico Šimonis, Povilas Stankevič, Voitech Gomaa, Mohamed A. E. Stirkė, Arūnas; Foods 2022; Vol. 11; Issue 11 Page 1556 under a Creative Commons license)).

Figure 2

A graph indicating typical pressure, temperature and time history during pressure-assisted thermal processing of conjugated linoleic acid (CLA)-enriched milk treated at 600 MPa/120 °C (tl, loading time; tc, compression time; th, holding time [78]) (reprinted from Combined Effect of Pressure-Assisted Thermal Processing and Antioxidants on the Retention of Conjugated Linoleic Acid in Milk. Martinez-Monteagudo, Sergio I., Saldaña, Marleny D.A.; Foods 2015; Vol. 4; Issue 2 Page 65–79 under a Creative Commons license).

Figure 3

Schematic representation of batch processing model for microwave sterilization, also known as coaxially-induced microwave pasteurization and sterilization (CiMPAS), where the packaging trays are arranged in carrier tray while kept immersed in hot/warm water inside the pressure vessel [25]. (Reprinted from Development of Bacterial Spore Pouches as a Tool to Evaluate the Sterilization Efficiency—A Case Study with Microwave Sterilization Using Clostridium sporogenes and Geobacillus stearothermophilus. Martinez-Monteagudo, Sergio I., Saldaña, Marleny D.A.; Foods 2020; Vol. 9; Issue 10, Page 1342 under a Creative Commons license.)