Quality and consumer acceptance of radio frequency and traditional heat pasteurised kiwi puree during storage

Radio Frequency Treatment of Food: A Review on Pasteurization and Disinfestation

Radio frequency (RF) is a novel technology with several food processing and preservation applications. It is based on the volumetric heating generated from the product's dielectric properties. The dielectric properties of each material are unique and a function of several factors (i.e., temperature, moisture content). This review presents a list of dielectric properties of several foods and describes the use of RF as an innovative technology for the food industry. This paper includes several examples of pasteurization, fungi inactivation, and disinfestation in selected food products. The aim of this review is to present the potential applications of RF in pasteurization and disinfestation and research needs that should be addressed. RF has been successfully applied in the inactivation of pathogens such as Salmonella spp., Listeria monocytogenes, and Escherichia coli in low- and high-moisture food. The disinfestation of crops is possible using RF because of selective heating. This process inactivates the insects first because of the different dielectric properties between the pests and the food. The products' final quality can be considerably better than conventional thermal processes. The processing time is reduced compared to traditional heating, and thermal damage to the food is minimized. The main drawback of the technology is the lack of uniform heating, mainly when the product is surrounded by a packaging material with different dielectric properties from the food.

Validation of Pasteurisation Temperatures for a Tomato-Oil Homogenate (salmorejo) Processed by Radiofrequency or Conventional Continuous Heating

Salmorejo is a viscous homogenate based on tomato, olive oil and breadcrumbs commercialised as a "fresh-like" pasteurised-chilled purée. Due to its penetration, dielectric heating by radiofrequency (RF) might improve pasteurisation results of conventional heating (CH). The objective was to validate the pasteurisation temperature (70-100 °C, at 5 °C intervals) for salmorejo processed by RF (operating at 27.12 MHz for 9.08 s) or conventional (for 10.9 s) continuous heating. The main heat-induced changes include: orangeness, flavour homogenisation, loss of freshness, thickening, loss of vitamin C and lipid oxidation. Both CH and RF equivalent treatments allowed a strong reduction of total and sporulated mesophilic microorganisms and an adequate inhibition of the pectin methylesterase, peroxidase and, to a lesser extent, polyphenol oxidase but did not inhibit the polygalacturonase enzyme. Pasteurisation at 80 °C provided a good equilibrium in levels of microbiological and enzymatic inhibition and thermal damage to the product. Increasing this temperature does not improve enzyme inactivation levels and salmorejo may become overheated. A "fresh-like" good-quality salmorejo can be obtained using either conventional or radiofrequency pasteurisers.

Comparison of high temperature-short time and sonication on selected parameters of strawberry juice during room temperature storage

The purpose of current research was to explore the effect of high temperature-short time (HTST) and different ultrasound times intervals on the strawberry juice for a period of 14 days. Strawberry fruits were treated at 72 °C for 15 s by HTST and also sonicated at 20 kHz and 100% amplitude for 5, 10, and 15 min. The main objective is to evaluate the effect of treatments and storage time on color, total antioxidants, total phenolics, ascorbic acid and microbial content of strawberry juice. Results showed that the increase in the sonication treatment time (from 5 to 15 min) showed a higher total phenolics, antioxidant capacity and ascorbic acid content. In addition, 15 min sonicated-strawberry juices showed a higher lightness values as compared to HTST treated strawberry juice. Sonication treatment showed a potential as a method to preserve and improve the phytochemical quality of strawberry juice during room temperature storage.

Effect of radio-frequency heating on microbial load, flavor, color, and texture profiles of Cordyceps militaris

BACKGROUND

Cordyceps militaris is a medicine and food dual-purpose mushroom extensively cultivated and consumed in East and Southeast Asia for centuries. However, it has an extremely short shelf life of 3-4 days at room temperature. C. militaris was pasteurized for 10, 20, and 30 min by radio-frequency (RF) at an electrode gap of 20 mm. The effect of RF heating on the microbial load, color, texture, and flavor attributes of C. militaris was evaluated and compared with those sterilized by conventional high-pressure steam.

RESULTS

RF heating contributed to good heating uniformity, uniform temperature distribution, and significant decrease in total microbial load. C. militaris heated by RF exhibited unnoticeable total color difference compared with unpasteurized ones, while those sterilized by high-pressure steam presented undesired and unacceptable browning. Insignificant differences in hardness and chewiness were observed after RF heating. Improvements in mushroom-like flavor occurred after 10 and 20 min of RF heating.

CONCLUSION

This study suggests that RF heating for pasteurization of edible mushrooms has promising prospects. Evaluation of RF heating on the taste and nutritional characteristics of edible mushrooms is needed in future work. © 2018 Society of Chemical Industry.