Electrifying Foods - A Breakthrough Towards Sustainability in Food Processing
We have come to a civilization where 50% of the Earth’s habitable land is dedicated to producing our food - agriculture. Surprisingly, one-third of all the foods ever produced is never consumed. Food loss and waste (FLW) poses a threat to our food security, especially with the human population that keeps increasing and climate change effects that become more apparent on crop yields. In addition to being land-intensive, the provision of food requires 70% of global water and 32% of global energy consumption. Therefore, it is beneficial to find solutions to eliminate FLW. One of the possible solutions is implementing technological breakthroughs in the food processing stage that aims to enhance food quality.
Pulsed Electric Field
Bare Electricity on Food
Non-thermal food processing technologies are superior compared to thermal counterparts in their abilities to preserve food quality as well as the nutrient contents inside it, and efficiency in energy use. Among them is pulsed electric field (PEF), which involves a high voltage power supply and treatment chamber with a set of electrodes. Food product placed between the electrodes is given short pulses of a high electric field with microsecond to millisecond intervals, and intensity of 10-80 kV/cm. The applied electric field will induce changes in electrically-sensitive food components, such as electrochemical reactions, molecule realignment, permeabilization of membranes, and reduction of activation energy. These will lead to microbial inactivation, substance extraction, biomolecule modification, improved reactions, accelerated aging in fermentation, and reduction of enzymatic activity.
Pasteurization, but Colder
PEF holds a promising alternative to the pasteurization of liquid foods. Applied electric field incurs potential difference across the transmembrane region of the cell membrane in microorganisms. When it exceeds the threshold value, the membrane will break down. This process is also known as electroporation. Strong electrical field intensity causes irreversible electroporation, which leads to cell death. PEF has been shown to successfully reduce E.coli cells by 5.53 log reduction in strawberry juice. This is done in just microseconds while maintaining the temperature below 50°C. Thus, it satisfies the FDA standard that requires 5 log reduction of pertinent microorganisms. PEF saves more time compared to other non-thermal technology, such as high-pressure processing (1 minute) and thermosonication (3 minutes). With lower operational temperatures, PEF has more capability in preserving nutrients than conventional pasteurization.
Another step of industrial food preservation is the inactivation of enzymes. Common heat-based methods are able to inactivate enzymes, but it comes with impairment of organoleptic properties. It is known that the ⍺-amylase enzyme is responsible for shortened food shelf life as digests starch into dextrin and maltose. PEF has been proven to inactivate ⍺-amylase by changing the enzyme’s active site. Unlike heating that affects the enzyme’s secondary structure and leads to protein denaturation, PEF only affects the tertiary structure and thus does not result in protein aggregation. PEF is also shown to have a 10% higher rate of inactivation than chemical inactivation.
Mass Transfer Enhancement
The pickling process aims to give out unique flavors and extended-shelf life of foods. This is generally done with dry-salted and wet-brine methods. In both methods, the permeation of seasonings depends on diffusional phenomena caused by a concentration gradient. However, the firm structure of food would impede this process, making it very time-consuming. In addition, there are risks of microbial overgrowth and deterioration of the brine. A study discovered that PEF treatment of lotus root before pickling process significantly increased water loss by 17% and shortened the time needed to reach the target of seasoning concentration by 12%. This is due to electroporation and destruction of tissue structure, resulting in less mass transfer resistance. The sample that was pre-treated with PEF also had a higher browning index, which is a more appealing property.
PEF pre-treatment of lotus root pickle
A life cycle assessment comparing PEF and thermal processing showed that PEF reduced the number of CO₂ emissions by 18.72% and fossil depletion by 19.83%. Besides food processing, ‘electro priming’ of wheat seeds using PEF improves water uptake, germination of seeds, and nutritional contents. At the end of food manufacturing, PEF can take a role in wastewater treatment and recovery of valuable compounds from food waste. PEF is a promising technology to be utilized for sustainable end-to-end food manufacturing. In the meantime, PEF needs a collaborative approach to develop adaptations for various purposes, combinations with other methods, and commercial scale-ups.
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