Abstract
Tomato-based processed foods are a key component of modern diets, usually combined with salt and olive oil in different ratios. For the design of radiofrequency (RF) and microwave (MW) heating processes of tomato-based products, it is of importance to know how the content of both ingredients will affect their dielectric properties. Three concentrations of olive oil and salt were studied in a tomato homogenate in triplicate. The dielectric properties were measured from 10 to 3000 MHz and from 10 to 90 °C. Interaction effects were studied using a general linear model. At RF frequencies, the dielectric constant decreased with increasing temperature in samples without added salt, but this tendency was reversed in samples with added salt. The addition of salt and oil increased the frequency at which this reversion occurred. At MW frequencies, the dielectric constant decreased with increasing temperature, salt, and oil content. The loss factor increased with increasing salt content and temperature, except in samples without added salt at 2450 MHz. Penetration depth decreased with increasing frequency and loss factor. Salt and oil contents have a significant effect on the dielectric properties of tomato homogenates and must be considered for the design of dielectric heating processes.
Highlights
IntroductionTomatoes and olive oil are two key components of the Mediterranean diet
Accepted: 13 December 2021Tomatoes and olive oil are two key components of the Mediterranean diet
The dielectric properties of homogenates of tomato, salt, and olive oil were measured at four frequencies relevant to industrial dielectric heating applications
Summary
Tomatoes and olive oil are two key components of the Mediterranean diet. Olive oil acts as an excipient food that increases the bioavailability of the nutrients present in tomatoes [1]. According to the European Commission, the production of processed tomatoes is expected to increase due to higher yields, whereas consumption will probably increase mainly due to growing demand for convenient and healthy food. EU exports of processed tomatoes are expected to increase 1% per year, with Spain, Italy, and Portugal contributing more than 90% of the production [2]. The thermal treatment of tomato-based products is usually carried out in heat exchangers; this operation produces characteristic cooked flavors while ensuring an extended shelf-life. The high temperatures at the surface of the tube and long processing times associated with conventional pasteurization are known to diminish the sensory and nutritional qualities of raw tomato products such as “salmorejo” or “gazpacho” [3]
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