No Major Differences Found between the Effects of Microwave-Based and Conventional Heat Treatment Methods on Two Different Liquid Foods

Abstract

Extension of shelf life and preservation of products are both very important for the food industry. However, just as with other processes, speed and higher manufacturing performance are also beneficial. Although microwave heating is utilized in a number of industrial processes, there are many unanswered questions about its effects on foods. Here we analyze whether the effects of microwave heating with continuous flow are equivalent to those of traditional heat transfer methods. In our study, the effects of heating of liquid foods by conventional and continuous flow microwave heating were studied. Among other properties, we compared the stability of the liquid foods between the two heat treatments. Our goal was to determine whether the continuous flow microwave heating and the conventional heating methods have the same effects on the liquid foods, and, therefore, whether microwave heat treatment can effectively replace conventional heat treatments. We have compared the colour, separation phenomena of the samples treated by different methods. For milk, we also monitored the total viable cell count, for orange juice, vitamin C contents in addition to the taste of the product by sensory analysis. The majority of the results indicate that the circulating coil microwave method used here is equivalent to the conventional heating method based on thermal conduction and convection. However, some results in the analysis of the milk samples show clear differences between heat transfer methods. According to our results, the colour parameters (lightness, red-green and blue-yellow values) of the microwave treated samples differed not only from the untreated control, but also from the traditional heat treated samples. The differences are visually undetectable, however, they become evident through analytical measurement with spectrophotometer. This finding suggests that besides thermal effects, microwave-based food treatment can alter product properties in other ways as well.

Microwave Processing: Current Background and Effects on the Physicochemical and Microbiological Aspects of Dairy Products

“…The authors have assembled a glass tube fitted across a waveguide in which raw milk was passed through and exposed to MW energy during gravity falling. Since then, several other studies on MW heating of milk have been performed, the majority of them focused on the assessment of the potential enhancement of the milk shelf‐life, the application of MW energy to inactivate milk pathogens and enzymes, the influence of MW treatment on nutritional and sensory aspects of milk, and the nonuniform temperature distribution during the MW treatment, in which many of these studies include a comparison with conventionally thermal treated milk samples (Chiu, Tateishi, Kosikowski, & Armbruster, ; Choi, Marth, & Vasavada, , ; Clare et al., ; Dehghan, Jamalian, Farahnaky, Mesbah, & Moosavi‐Nasab, ; Dumuta, Giurgiulescu, Mihaly‐Cozmuta, & Vosgan, ; Géczi et al., ; Iuliana, Rodica, Sorina, & Oana, ; Jaynes, ; Kudra, de Voort, Raghavan, & Ramaswamy, ; Lin & Ramaswamy, ; Manjunatha, Prabha, Ramachandra, Krishna, & Shanka, ; Rasooly, Hernlem, He, & Friedman, ; Rodríguez‐Alcalá, Alonso, & Fontecha, ; Sieber, Eberhard, & Gallmann, ; Tremont et al., ; Villamiel et al., ; Wang & Guohua, ).…”

“…() observed a reduction of the fat content in milk during MW heating. Milk lipids may undergo chemical and physical changes during processing and storage, such as auto‐oxidation and formation of trans FAs (TFAs; Semma, ), and this fact may be an explanation for a decreasing fat content (Mishra & Ramchandran, ); however, such reduction in fat content was not observed in other similar studies (Dehghan et al., ; Géczi et al., ).…”

“…Novel thermal technologies such as dielectric heating by microwave (MW) and radio-frequency systems promote a volumetric heating, that is, the heat generated occurs inside the food, thereby obtaining higher quality products with greater thermal efficiency when compared to conventional thermal processes (Bhushand et al, 2017;Mishra & Ramchandran, 2015). Because the first study reported on the use of a MW system for milk pasteurization (Hamid, Boulanger, Tong, Gallop, & Pereira, 1969), many studies have been carried out on the pasteurization and sterilization of different food products (Géczi, Horváth, Kaszab, & Alemany, 2013;Laguerre et al, 2011;Lin & Ramaswamy, 2011;Manjunatha, Prabha, Ramachandra, Krishna, & Shankar, 2012;Pina-Pérez, Benlloch-Tinoco, Rodrigo, & Martinez, 2014;Rasooly, Hernlem, He, & Friedman, 2014;Tremonte et al, 2014).…”

Development of biodegradability indicators for microwave sludge conditioning

“…Thermal effect is expressed in the increase of internal pressure of intracellular liquor caused by internal heating and rapid evaporation, which altogether can lead to cell wall disruption (Géczi et al, 2013). The non-thermal effect of high frequency electromagnetic field contributes to alter the structure of macromolecules with polarization of side chains and breaking of hydrogen bounds (Park et al, 2004;Lakatos et al, 2005).High efficiency of MW treatments in the biomaterial processing and also on the rate of chemical reactions is often explained by the non-thermal effects of microwaves due to the direct interaction of electromagnetic field with molecules.…”

Molecular Mechanisms Contributing to the Growth and Physiology of an Extremophile Cultured with Dielectric Heating

“…T he impact of microwave frequency (300 MHz to 300 GHz) electromagnetic fields on living organisms is of significant interest across multiple industries, including medical, food, and biotechnology (1)(2)(3)(4)(5). However, confirmation that a biological effect results from exposing live cells to an electromagnetic field has yet to be definitively demonstrated.…”