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Cold pasteurization and supercritical CO2

Research and development in the agri-food chain. Public attention is generally low and investments modest, in comparison with other sectors. However, food technology plays a crucial role, not only in making ultra-processed foods but also in preserving the substances and properties characteristic of agricultural and botanical raw materials. In some cases, even better than 'traditional' production methods. A couple of examples to follow, cold pasteurization and supercritical CO2 extraction.

DPCD, the 'cold pasteurization'

The food industry makes extensive use of technologies such as pasteurization and freeze-drying, just to name a few. Conversely, some technologies with great potential fail to overcome that veil of distrust and skepticism that continues to surround them. These include equipment and systems that make use of carbon dioxide (or CO2) in a liquid or supercritical state.

Cold pasteurization is the common name of the treatment known by the acronym DPCD (Dense Phase Carbon Dioxide). A process defined as 'non-thermal' in which the CO2 in the supercritical state, at a temperature between 35-50 ° C and a variable pressure between 70 and 500 bar, is placed in contact with the food in order to sanitize the product. CO2 at ambient pressure is known for its inhibition activity on microbial growth, with effects that last for more or less long periods, attested by various scientific studies. 

The state of CO2 it can have significant influences on antimicrobial activity. The pressure used makes it possible to act on the inactivation of microorganisms (through rupture mechanisms of cell membranes) and the inactivation of bacterial enzymes, essential for their metabolism and the variation of pH in the bacterium. Its use is preferred on foods which by their natural composition are sensitive to heat, such as fruit juices and milk. The low temperature allows to maintain the nutritional profile in terms of macro and micronutrients (eg polyphenols and vitamins). 

The use of the DPCD it keeps intact the sensorial attributes of freshness typical, for example, of fresh fruit. Without affecting the sugar component with thermal processes responsible for that 'cooked' taste that is perceived when consumed in some foods treated with conventional thermal technologies. In matrices with a fat component, the use of CO2 also allows to contain the phenomena of rancidity, preventing the development of its unpleasant aroma. In fermented products such as wine and beer, the treatment with CO2 can then inhibit the activity of any yeasts present in the bottling phase. Also offering where required, with appropriate dosages, a pleasant sparkling note. This type of process, although known to the applied research sector, still finds little attention in the food industry.

Supercritical CO2, the non-alcoholic extraction without solvents 

Carbon dioxide, usually known in the gaseous phase, when subjected to a minimum pressure of 72 bar and a temperature of 31 ° C, it assumes intermediate properties between those of a liquid and those of a gas that allow for multiple uses. Due to its chemical characteristics this fluid is comparable to an organic solvent, very similar to the world of lipophilic substances.

The most 'traditional' applications of supercritical CO2 relate to the removal of caffeine from coffee, the extraction of the bittering component from hops for the brewing industry, the treatment of cork to reduce the possible defect of the 'cork' scent in the wines thus bottled (due to the presence of the trichloroanisole). Its favorite function is therefore that of extraction, which can also allow its use in the extraction of valuable vegetable oils (its costs are not negligible) or essential oils and aromatic components from medicinal plants or spices. 

The advantages that derive from the use of supercritical CO2 are first of all its complete non-toxicity and low operating temperature, which allows this technology to be defined with the adjective 'cold'. The products thus obtained are totally free of residual solvent, as well as having a very high degree of purity. The application of this technology can therefore allow to obtain ingredients and products of high quality quality. Keeping intact the olfactory imprint that characterizes the plant undergoing treatment and the bioactive properties of its components most sensitive to all heating technologies. 

In this sense interest in the use of supercritical fluids in the extraction of non-psychrotropic cannabinoids such as cannabidiol or CBD and aromatic terpenes from inflorescences of hemp industrial (Cannabis sativa L.) for the development of formulations in which the beneficial properties of this 'molecular blend' are expressed to the maximum, thanks to the low impact of the production technology.

Deborha Decorti

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Food Technologist, Ph.D in Food Science, specializing in 'New Product Development' at the European Institute of Innovation and Technology. Expert in R&D with unconventional green technologies, with attention to the values ​​of health, sustainability and circular economy


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