Research and Development in the Agri-Food Supply Chain. Public attention is generally limited and investment modest, compared with other sectors. Food technology, however, plays a crucial role, not only in producing ultra-processed foods, but also in preserving the characteristic substances and properties of agricultural and botanical raw materials. In some cases, it even proves superior to so-called ‘traditional’ production methods. A couple of examples follow: cold pasteurisation and supercritical CO2 extraction.
DPCD, the ‘Cold Pasteurisation’
The food industry makes extensive use of technologies such as pasteurisation and freeze-drying, to name just a few. Conversely, some technologies with great potential fail to overcome the veil of distrust and scepticism that continues to surround them. Among these are the equipment and systems that use carbon dioxide (or CO2) in its liquid or supercritical state.
Cold pasteurisation is the common name for the treatment known by the acronym DPCD (Dense Phase Carbon Dioxide). It is a ‘non-thermal’ process in which CO2 in a supercritical state, at a temperature between 35 and 50°C and a pressure ranging from 70 to 500 bar, is brought into contact with the food in order to sanitise the product. CO2 at ambient pressure is known for its inhibitory activity on microbial growth, with effects that persist for variable periods, as confirmed by several scientific studies.
The state of the CO2 can have a significant influence on its antimicrobial activity. The pressure applied acts on the inactivation of microorganisms (through mechanisms of cell membrane disruption) and on the inactivation of bacterial enzymes, which are essential for their metabolism and for changes in bacterial pH. Its use is preferred on foods that are naturally heat-sensitive, such as fruit juices and milk. The low temperature allows the nutritional profile in terms of macro- and micronutrients (e.g. polyphenols and vitamins) to be maintained.
The use of DPCD preserves the typical sensory attributes of freshness, as in fresh fruit, without altering the sugar component through thermal processes responsible for the ‘cooked’ taste often perceived in some foods treated with conventional thermal technologies. In matrices containing fat, the use of CO2 also helps to limit rancidity phenomena, preventing the development of unpleasant odours. In fermented products such as wine and beer, CO2 treatment can inhibit the activity of any yeasts present at the bottling stage. It can also, when required and properly dosed, provide a pleasant sparkling note. Although known in the field of applied research, this process still receives little attention within the food industry.
Supercritical CO2: Solvent-Free, Alcohol-Free Extraction
Carbon dioxide, typically known in its gaseous phase, when subjected to a minimum pressure of 72 bar and a temperature of 31°C, acquires properties intermediate between those of a liquid and a gas, which enable multiple applications. Due to its chemical characteristics, this fluid can be compared to an organic solvent, highly compatible with substances of a lipophilic nature.
The more ‘traditional’ applications of supercritical CO2 concern the removal of caffeine from coffee, the extraction of bitter components from hops for the brewing industry, and the treatment of cork to reduce the possible defect of the ‘cork taint’ in bottled wines (caused by the presence of the molecule trichloroanisole). Its preferred function is therefore that of extraction, which also allows its use in the extraction of high-quality vegetable oils (its costs being not negligible) or essential oils and aromatic compounds from medicinal plants or spices.
The advantages deriving from the use of supercritical CO2 are primarily its complete non-toxicity and the low operating temperature, which allows this technology to be defined as ‘cold’. The products obtained are entirely free from residual solvents and possess an extremely high degree of purity. The application of this technology can therefore yield ingredients and products of outstanding qualitative value, preserving the olfactory imprint characteristic of the treated plant and the bioactive properties of its most heat-sensitive components.
In this regard, there is strong and current interest in the use of supercritical fluids for the extraction of non-psychoactive cannabinoids such as cannabidiol or CBD, and aromatic terpenes from the inflorescences of industrial hemp (Cannabis Sativa L.), for the development of formulations in which the beneficial properties of this ‘molecular blend’ are fully expressed thanks to the low impact of the production technology.
Deborha Decorti
Biologist, expert in molecular genetics.
