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In this study the effect of PEF pre-treatment on the microstructure of freeze-dried strawberry dices was investigated. The PEF treatment has been performed at an electric field intensity of 1.07 kV/cm and a specific energy input of 1 kJ/kg. The samples were freeze-dried at a temperature of 45 °C and a pressure of 1 mbar. The microstructure of dried material was evaluated by different physical and optical methods, such as SEM, μ-CT and thermogravimetry. Moreover, mechanical and acoustic properties as well as the colour of processed material have been analyzed. PEF pre-treated strawberry dices showed a more uniform shape, a better retention of volume and a visual better quality compared to untreated ones. Moreover, PEF pre-treatment led to a more homogeneous distribution and a greater thickness of pores. In accordance, analysis of textural properties evidenced that PEF treated freeze-dried strawberry dices were crispier than untreated ones. Measurement of L*a*b*-values showed that PEF treated material was characterized by a more preserved colour after freeze-drying than untreated ones.
While the Food and Biotechnology industries often use unit operations that have been known for some time, sometimes these processes are not efficient or sustainable. The need to develop more efficient processing lines to obtain higher quality products is of utmost importance. Over the last years, pulsed electric fields (PEF) processing has attracted the interest of numerous researchers and companies due to its ability to reduce processing time, preserve thermolabile compounds, which are responsible for the aroma, nutritional and bioactive properties of food products.
Therefore, in this article, some of the most important studies regarding the application of PEF technology in food and biotechnology processing is discussed.
The study aimed for the analysis of the impact of pulsed electric field (PEF) pre-treatment on convection (CD) and microwave (MW-CD) assisted air drying. Drying kinetics acceleration and retention of bioactive compounds of PEF pre-treated carrots and apples has been demonstrated. Moreover, the direct and indirect environmental energy impacts of CD and MW-CD technologies with consideration of bioactive compounds preservation has been evaluated. PEF assisted CD and MW-CD demonstrated lower energy use, especially for indirect energy consumption, in the case of carotenoids preservation in dried carrots.
Currently, the modelling of drying processes of plant tissues pre-treated by pulsed electric field (PEF) is following experimentally identified curves or separate heat and mass transfer and diffusion models with different levels of accuracy. This research had two major objectives: mathematical modeling and control of drying process of different vegetables pretreated by PEF during convective drying. The mathematical modeling was based on Luikov's heat and mass transfer model along with properties of different vegetables. Computer modelling was done using the difference method for predicting moisture and the temperature potentials of untreated and PEF-treated vegetables. The formulation and the solution procedures were applied to simulate the simultaneous heat and mass transfer in selected vegetables subjected to the convective drying. Suggested model had a good correlation with experimental results. Moreover, cell disintegration index can be used as a controllable parameter in heat and mass transfer models to predict drying behavior of potato, onion, and carrot tissues. Obtained drying models can be used as a mathematical tool to predict drying behavior for various types of agricultural products pre-treated by pulsed electric field.
Applications of pulsed electric fields for processing potatoes: Examples and equipment design
(2022)
In the last two decades, pulsed electric fields (PEF) have successfully been introduced into the food industry, as one of the most promising and "game changing" technologies. This review is devoted to the recent applications of pulsed electric fields used in processing potatoes. The potato processing market size was estimated to be ca. USD 24.83 billion (2018) and with an annual growth rate of 5.2%. The physicochemical characteristics of potatoes and the specificity of potato processing lines makes a pulsed electric field very versatile and flexible allowing one to achieve different technological aims by its implementation into technological lines. In this paper, a short analysis of the potato structure and its nutritional properties, applications of moderate electric fields, ohmic heating, and pulsed electric fields are presented. Moreover, the basic electroporation effects, metabolic responses, texture modification and different PEF assisted processes applied to the potato are discussed. Finally, some examples of commercial applications and a brief description of the available equipment for the PEF processing of potatoes are presented.
This chapter presents the mechanism of the enhancement of freezing by means of ultrasound (US). It has been demonstrated that the effects of US are a rather complex issue. In theory, ultrasound creates cavitation bubbles throughout the volume of the product, which promotes nucleation of the ice and crushes the crystals already present in food. They can also enhance convective heat transfer to the cooling media, thereby accelerating freezing. Moreover, it has been shown that ultrasound reduces the degree of supercooling before nucleation in frozen food. Additionally, numerous experimental studies indicate that ultrasound assisted freezing is a good method to achieve homogenous crystallizations, reduce the deteriorating effect of freezing on food, and thus improve quality after thawing.
Olive oil holds significant importance in the European diet and is renowned globally for its sensory attributes and health benefits. The effectiveness of producing olive oil is greatly influenced by factors like the maturity and type of olives used, as well as the milling techniques employed. Generally, mechanical methods can extract approximately 80% of the oil contained in the olives. The rest 20% of the oil remains in the olive waste generated at the end of the process. Additionally, significant amounts of bioactive compounds like polyphenols are also lost in the olive pomace. Traditionally, heat treatment, enzymes, and other chemicals are used for the enhancement of oil extraction; however, this approach may impact the quality of olive oil. Therefore, new technology, such as pulsed electric field (PEF), is of great benefit for nonthermal yield and quality improvements.