Application of microwave and ohmic heating for pasteurization of cantaloupe juice: microbial inactivation and chemical properties

Abstract

BACKGROUND: Cantaloupe melon (Cucumis melo L.) is one of the most important dessert fruits and is cultivated in many countries of the world. The effects of microwave (400 and 800 W for 110 s), ohmic (100 and 200 V for 110 s) and conventional heating (27-75 ∘ C for 30 min) treatments on inactivation of Escherichia coli, Salmonella Typhimurium, S. Enteritidis and Staphylococcus aureus pathogens; pH and degradation of vitamin C, -carotene and phenolic compounds of cantaloupe juice were investigated. RESULTS: As time passed, all of the treatments resulted in significant (P ≤ 0.05) decreases in the number of pathogens and vitamin C, -carotene and phenolic compound content, whereas the pH of samples did not show significant changes. The mentioned parameters were more reduced by increasing the power, voltage and temperature of ohmic, microwave and conventional heating treatments, respectively. Comparison of the results for conventional heating with those of ohmic and microwave heating revealed that the complete inactivation time of pathogens by the two latter treatments was much shorter than that of the former. After 20 s, the effect of ohmic heating at 200 V on decreasing vitamin C content was significantly (P ≤ 0.05) higher than that of the other treatments. The amounts of -carotene and phenolic compounds showed the most reduction under 800 W microwave treatment. CONCLUSION: The results obtained for conventional, ohmic and microwave heating treatments indicated a higher degradation of -carotene and phenolic compounds and a lower loss of vitamin C in the former. -Carotene determination -Carotene was extracted with hexane-acetonitrile-ethanol solution and the content was measured at a wavelength of 480 nm (UV-visible; Philips, Cambridge, UK). The result was expressed as micrograms of -carotene per gram of dry solids. 41 J Sci Food Agric 2019; 99: 4276-4286

The influence of Ohmic‐vacuum heating on phenol, ascorbic acid and engineering factors of kiwifruit juice concentration process

“…Results showed that the AA content of concentrated samples was lower than the fresh juice (370.9 ± 23.6 mg AA/100 mL). Generally, the heating process reduced the AA content in fruit juice because vitamin C is sensitive to heat and environmental conditions (Hashemi et al ., 2019). AA declines in OHVC treatments were lower than OHAC ( P < 0.05).…”

Microbial inactivation by ohmic heating: Literature review and influence of different process variables

“…Several authors have compared the effects of using high and low electric fields on microorganism inactivation. Won et al (2002), Uemura and Isobe (2002), Yildiz and Baysal (2006), Kim, Park, andKang (2018), Hashemi, Gholamhosseinpour, andNiakousari (2019) and found significant reductions in viable cells at higher electric fields; this behaviour was also observed by Shao et al (2019). Moreover, the latter authors showed that the recovery of injured cells is slower at higher voltages.…”

“…The greater the electric field and shear rate, the lower the inactivation time for a 5-log reduction. Moreover, Hashemi, Gholamhosseinpour, et al (2019) and Hashemi, Mahmoudi, et al (2019) demonstrated that an increase in the electric current had a significant impact on reducing microbial species. This effect was higher for Zygosaccharomyces rouxii than for the bacterial and fungal species analysed, which may suggest that yeasts are more susceptible to electric effects.…”

Comparative analysis of ohmic and conventional heat‐treated carrot juice

“…This may be because β-carotene is prone to degradation and more precisely to isomerization, especially at high temperature, and oxidation, due to the occurrence of oxygen in food (Hashemi et al, 2019;Pénicaud et al, 2011):…”