## 1 Introduction  
The hemp plant (_Cannabis sativa_ L.) is widely cultivated and used in industrial production because of its multi-functionality. It is possible to obtain isolated proteins, fibres for paper and textile, oil from seeds and flours either for food or for cosmetics and pharmaceutical industries [1, 2, 3]. Particularly, the oil from hemp seeds has a high nutritional profile because of polyunsaturated essential fatty acids (EFAs) contained in this oil, which are linoleic acid (C18:2\(\omega\)o) and \(\alpha\)-linolenic acid (C18:2\(\omega\)3) contained in the hemp seed oil at a ratio of 3:1 [4]. In addition, hemp seed oil has a rare acid, \(\gamma\)-linolenic acid, that is advantageous for hormonal balance. Linolenic acid also a positive impact on rheumatoid arthritis, atopic dermatitis, and allergies and has anti-inflammatory, antihypertension, anti-vasoconstrictive, and anti-cancer effects [5]. Additionally, the oil is suitable for both human nutrition and the preparation of several oils and body creams, thanks to its good absorption through the skin. Tocpherols contained in hemp oil are also used to reduce the risk of cardiovascular diseases, cancers and skin-ageing alterations within the blood vessels [6, 7], and the well-balanced quantity of linolenic acid and \(\alpha\)-linolenic acid gives hemp seed oil unique healthy properties [5]. Hemp oil is generally produced by solvent extraction or by cold pressing. The first type of extraction uses solvents, and for this reason is dangerous for the environment and can contain toxic residue. Thus, in the last few years, cold pressing has come to be preferred despite the lower yield of extraction [8]. The cold-pressing extraction can recover up to 65% of the oil in the seeds, and 35% of the available oil remains in the seed cake, but a high chlorophyll pigment content is also present in the oil [9]. The pigments modify the oil colour from dark to light green and promote the oxidation of lipids, which leads to the degradation of hemp oil quality, requiring its storage in dark or matt packaging [9; 10]. Therefore, other extraction techniques are investigated by researchers such as supercritical extraction with CO\({}_{2}\) (SFE-CO\({}_{2}\)), which can give an oil of very high quality also in the presence of an ultrasound pre-treatment [8; 10]. SFE-CO\({}_{2}\) is becoming an important technology to obtain oil with a high purification degree for nutritional purposes or pharmaceutical applications. The solvent used is nontoxic and easy to separate from the extract, and moreover, it is tunable; the use of ultrasounds, coupled with this green technique, can improve the yield of oil obtained because they can disrupt the oil bodies [8]. The ultrasonic pretreatment was also evaluated to extract oil with SFE-CO\({}_{2}\) from hemp seeds and other types of seeds [8; 11; 12; 13]. The use of ultrasonic conditions reduces the extraction time [12; 13; 14], but when ultrasounds are used, they generate heat, the amount of which is directly proportional to the ultrasonic power used. It should be pointed out that In recent years, food industries have also focused their attention on the use of hemp proteins because hemp proteins consist of albumin and edestin, and these are an excellent source of digestible amino acids [15; 16; 17; 18]. The amount of protein inside the hemp seeds is around 25%, and it is possible to extract them as hemp protein isolates after extracting the oil from the seeds and after performing particular steps to isolate them [15; 17]. This type of protein can be used for different foods, such as baked goods [19], food foams, or emulsions [15; 17; 20; 21] because they are also easily digested [20; 22]. Unfortunately, hemp proteins have low solubility at neutral pH, making their use limited in systems such as foams or emulsions [20]. [PERSON] and co-workers [21] studied the stability of hemp protein emulsions to find a trend with pH and compare their functional properties with those of soy protein isolate.