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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.
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.
Pulsed electric field (PEF) treatment consists of exposing food to electrical fields between electrodes within a treatment chamber, which can improve the preservation of fresh-like products such as milk. Although several studies support the use of PEF technology to process milk at low temperature, these studies reported microbial reductions of around 3 log10 cycles and also indicated a limited impact of PEF on some endogenous and microbial enzymes. This scenario indicates that increasing the impact of PEF on both enzymes and microorganisms remains a major challenge for this technology in milk processing. More recently, combining PEF with mild heating (below pasteurization condition) has been explored as an alternative processing technology to enhance the safety and to preserve the quality of fresh milk and milk products. Mild heating with PEF enhanced the safety of milk and derived products (3 log10–6 log10 cycles reduction on microbial load and drastic impact on the activity enzymes related to quality decay). Moreover, with this approach, there was minimal impact on enzymes of technological and safety relevance, proteins, milk fat globules, and nutrients (particularly for vitamins) and improvements in the shelf-life of milk and selected derived products were obtained. Finally, further experiments should consider the use of milk processed by PEF with mild heating on cheese-making. The combined approach of PEF with mild heating to process milk and derived products is very promising. The characteristics of current PEF systems (which is being used at an industrial level in several countries) and their use in the liquid food industry, particularly for milk and some milk products, could advance towards this strategy.
Optimization of important drying parameters with PEF pretreatment was carried out using Hermetia illucens larvae tissue. Three level factorial design of response surface methodology was used for the study varying specific PEF energy input 10–20 kJ/kg and drying temperature of 50–90 °C. Important average H. illucens larvae temperature during the drying process was obtained by numerical simulation from Luikov drying model. Consumption of drying energy was affected more by the drying temperature, than by the PEF energy. This indicated that range between 81 and 84 °C drying temperature and range from 11.2 to 13.1 kJ/kg of specific PEF energy input may be considered as optimal processing window for larvae drying.
Insect production for food and feed purposes is rapidly emerging in Europe, in many cases relying on existing processing methods for blanching, freezing, drying, fractionating, but also seeking for more efficient and beneficial biomass treatment methods. Current study is aimed to explore the application of Pulsed electric fields (PEF) pretreatment of insect biomass (Hermetia illucens) for drying and oil extraction enhancement. The study demonstrates an increase in the drying rate of larvae pre-treated with PEF at 2 and 3 kV/cm; 5, 10 and 20 kJ/kg wet basis. No effect on fatty indices and amino acids profile were determined, but more free total amino acids especially at PEF with E = 2 kV/cm and 20 kJ/kg, were identified in press cake after pressing. Results from this study show, that PEF could be used as a pre-treatment before drying of insect mass to increase the drying rate or to decrease the drying time and the content of functional ingredients under gentle conditions. Slight increase in the oil yield after PEF treatment allows to propose this technique for oil extraction improvement.
Applicability of Pulsed Electric Field (PEF) Pre-Treatment for a Convective Two-Step Drying Process
(2020)
Available literature and previous studies focus on the Pulsed Electric Field (PEF) parameters influencing the drying process of fruit and vegetable tissue. This study investigates the applicability of PEF pre-treatment considering the industrial-scale drying conditions of onions and related quality parameters of the final product. First, the influence of the PEF treatment (W = 4.0 kJ/kg, E = 1.07 kV/cm) on the convective drying was investigated for samples dried at constant temperatures (65, 75, and 85 °C) and drying profiles (85/55, 85/65, and 85/75 °C). These trials were performed along with the determination of the breakpoint to assure an industrial drying profile with varying temperatures. A reduction in drying time of 32% was achieved by applying PEF prior to drying at profile 85/65 °C (target moisture ≤7%). The effective water diffusion coefficient for the last drying section has been increased from 1.99 × 10−10 m2/s to 3.48 × 10−10 m2/s in the PEF-treated tissue. In case of the 85/65 °C drying profile, the PEF-treated sample showed the highest benefits in terms of process efficiency and quality compared to the untreated sample. A quality analysis was performed considering the colour, amount of blisters, pyruvic acid content, and the rehydration behavior comparing the untreated and PEF-treated sample. The PEF-treated sample showed practically no blisters and a 14.5% higher pyruvic acid content. Moreover, the rehydration coefficient was 47% higher when applying PEF prior to drying.
The study investigated the potential of pulsed electric fields (PEF) technology application for the improvement of cell disintegration and subsequent extraction/fractionation of cyanobacteria Arthrospira maxima into valuable components (phycocyanin, proteins, oils and carbohydrates). Pulsed electric fields were applied to fresh A. maxima suspension, dried powder and dried sticks in combination with water as extraction solvent and freeze-thawing. Pulsed electric fields application for cell disruption reached approximately 90% increase of C-phycocyanin extraction compared to bead milling. Obtained fractions of phycocyanin and bulk proteins were also of higher purity and had twice lower environmental impact than similar fractions obtained without Pulsed electric fields treatment. Extracts with improved purity can be directly applied in pharma and food industry without any further processing and purification steps.
The aim of this work was to investigate the potential of PEF technology for green extraction of microalgal pigments and lipids from fresh Chlorella sorokiniana suspensions. Efficiencies of PEF treatment and different solvent systems application to C. sorokiniana were compared to efficiencies of untreated biomass extraction. Differences in chlorophyll extraction of untreated and PEF treated C. sorokiniana were only seen at short extraction times. Beneficial PEF-effect was minimised for long-time extractions of larger algae quantities where yields aligned. Extraction attempts on C. sorokiniana lipids did not show increased extractability after PEF treatment, which underlined the statement of PEF representing a rather ineffective disruption method for microalgae holding rigid cell walls.
Dehydration is a technique that has been used since ancient times. The need to develop more efficient processes to obtain dehydrated foods of higher quality from the organoleptic and nutritional point of view has led to the study of different techniques. For instance, convection drying, freeze-drying, spray drying, vacuum drying, microwave vacuum drying, infrared radiation drying, osmotic dehydration, among others have been investigated.
Over the last years, pulsed electric fields (PEF)-assisted drying has attracted the interest of several researchers due to its ability for reducing drying time, preserving at the same time some 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-assisted drying in food processing will be discussed.
Pulsed electric fields (PEF) application enables cell disintegration and microbial decontamination of food products. Recent developments of pulsed power systems have supported successful technology transfer, from lab scale to industrial application, of PEF processing for fruit juice and vegetable processing. Ongoing equipment design research will result in increased treatment capacities and development of additional applications of PEF to foods. Future PEF processing applications for shelf life extension of protein-based drinks, dressings, soups, dairy products, and beer are likely, as are applications for extraction improvements in wine, micro- and macro-algae production. Therefore this chapter is introducing the history of industrial application of PEF technology. Moreover, it is giving an overview of current applications. Finally, the current status of patents and a discussion of advantages and challenges of this emerging technique will be presented.