It is recognized that fruit consumption constitutes a large contribution of macronutrients, micronutrients, phytochemicals, and structural carbohydrates ^[1][2][3][15,24,25] (Figure 1), resulting in health benefits. According to dietary guidelines, fruit intake decreases excessive oxidative stress, preventing chronic and metabolic diseases while also acting on energy intake ^[4][26].

Indeed, fruits are recognized as fundamental sources of vitamins, minerals, dietary fiber, and antioxidants. Their nutritional value and sensory characteristics depend on species, variety, cultivation (conventional or biological), soil, climatic conditions, storage, transport, and shelf life. Currently, there is a tendency to combine different fruits to increase both the flavor and the contribution of nutritional qualities ^[5][6][27,28].

Fruits are important sources of vitamins and minerals, mainly vitamin C and the B complex, and precursors of vitamin A, as well as providing antioxidants ^[6][7][10,28].

Minerals are essential in human health as they affect the development of bones and teeth, in addition to being related to electrolyte and water balance, metabolic catalysts, oxygen binding, and hormonal functions ^[8][29]. Fruits can contain significant amounts of important minerals such as: potassium, particularly bananas, blackcurrants, and blackberries; magnesium, of which the highest content is recorded in blackberries; and iron, where the strawberry stands out. However, they are low in sodium and selenium. It is also observed that berries as a whole are an important source of minerals, of which the main minerals found are phosphorus, potassium, calcium, magnesium, and iron (Table 1).

Without the ability to synthesize vitamins, these minerals are essential for the proper functioning of the human body due to their antioxidant potential ^[12][30]. Ascorbic acid, or vitamin C, exists mainly in red fruits, such as strawberries, cherries, red raspberries, black raspberries, blackberries, cranberries, and blueberries, with a higher incidence in black currants, oranges, and papayas, which also register considerable levels of vitamin C. Vitamin A is not found abundantly in fruits, with a few exceptions, such as mangos, papayas, melons, and even watermelons. Vitamin B6 (riboflavin) is not present in large amounts in fruits, but appears in appreciable amounts in blueberries, cherries, strawberries, cranberries, and plums (Table 1).

The benefits of a diet rich in dietary fiber have long been known ^[13][14][34,35], namely in physiological responses to satiety, gastrointestinal tract physiology ^[14][35], lower risk of colorectal cancer, lower total and LDL cholesterol, and cardiovascular disease ^[15][36]. The term dietary fiber consists of polysaccharides (cellulose, hemicellulose, pectins, gums, mucilages) and lignin ^[5][13][16][27,34,37]. The fiber content in the fruit ranges from 1 to 3.17 g/100 g FW, with pears and figs showing the highest amounts, 3.1 and 2.9 g/100 g FW, respectively ^[9][31]. The red fruits were recorded to possess lower fiber contents, where the cranberries present the highest fiber content (35.7 mg/100 g FW), followed by the raspberries (5.8–6.5 mg/100 g FW) and the blackberries (4.5–5.3 7 mg/100 g FW) ^[5][9][10][27,31,32].

Glucose, sucrose, and fructose are the main sugars in the fruits, and although there are significant variations in their amount, according to Septembre–Malaterre et al. ^[7][10], the number of sugars in the fruit can vary between 5 and 22% of fresh weight, with citrus fruits among those with the lowest percentage of sugars and bananas with the highest. Mikulic–Petkovsek et al. ^[17][38] determined that fructose and glucose are the main sugars present in red fruits; not detecting sucrose in blackberry and raspberry fruits.

Phenolic compounds are one of the major classes of secondary plant metabolites and are among the most abundant natural antioxidants in the diet. Fruit is one of the foods richest in polyphenols, contributing to about half of the total nutritional intake ^[18][39]. They are associated with the prevention of numerous pathologies associated with oxidative stress, acting as antioxidants, also exhibiting antibacterial, antitumor, antimalarial, and antiviral characteristics, among others ^[1][19][15,40]. The phenolic potential of fruits depends on many factors, of which genetic attributes, maturity stage, and growing conditions are of primary importance ^[1][20][15,41].

About 8000 different plant phenolic structures are known ^[21][42], which are divided into major families such as phenolic acids, flavonoids, and stilbenes ^[7][22][10,43]. In red fruits, most of the phenolics present belong fundamentally to two classes: phenolic acids and anthocyanins, although each species has its profile ^[1][15]. For example, blueberries are rich in quercetin and caffeic acid (31.0–83.0 and 2.0–27.35 mg/kg fresh weight, respectively) ^[23][24][25][44,45,46], while lingonberries are rich in p-coumaric and ferulic acid (37.6–251.1 and 16.2–221.7, respectively) ^[26][27][47,48].

Among the flavonoids, flavanols and proanthocyanidins are the most present in the human diet. In fruits, catechins are represented with high content in apricots and cherries ^[28][29][49,50]. Proanthocyanidins are particularly abundant in cranberries (418.8 mg/100 g fresh weight), blueberries (179.8–331.9 mg/100 g fresh weight), plums (215.9–256.6 mg/100 g fresh weight), apples (69.6–141 mg/100 g fresh weight), blackcurrants (147.8 mg/100 g fresh weight), and strawberries (145 mg/100 g fresh weight) ^[30][51]. Anthocyanins are also abundant in fruits, found mainly in the fruit skin. Anthocyanin content is related to the increasing color intensity as the fruit ripens ^[31][32][52,53]. Grapes are the main dietary source of anthocyanins. The monomeric anthocyanins in grape skin extracts were mainly malvidin, particularly the malvidin-3-glucoside (1.40–7.09 mg/g of skin and 0.62–6.09 mg/g of skin, respectively) ^[33][54].

Lignans are found in relatively low concentrations in various fruits, having a positive impact on the prevention of heart disease, mamma cancer, and osteoporosis ^[34][55]. The highest content of lignan is observed in pears (15.56 mg/100 g food), apricots (11.57 mg/100 g food), grapefruits (7.44 mg/100 g food), peaches (6.83 mg/100 g food), and strawberries (6.2 mg/100 g food) ^[35][56].

Stilbenes are rarely present in human food. Trans-resveratrol can be found in grape skins with well-known beneficial health effects ^[36][37][57,58], namely in the prevention of human cardiovascular diseases. The highest concentration of this phenolic compound was found in grape skin, with a higher concentration in the red compared to the white varieties ^[38][59].

The chemical composition of the fruit affects the sensory characteristics of the juice. According to Francis and Newton ^[39][60], aroma results from complex interactions of numerous chemical compounds. Essentially, the cultivar ^[40][41][42][61,62,63], agricultural practices (conventional vs. organic) ^[43][44][64,65], post-harvest treatments, and the different techniques used to extend the shelf life of fruit and fruit juices ^[45][46][66,67], lead to variations in their sensory characteristics. Several techniques can be used to preserve the shelf life of this type of product, including thermal and non-thermal processing methods. However, their use should prevent the loss of the sensory properties of the juice or limited effectiveness of the treatment, since, in the search for the development of differentiating products, the mixed fruit juices are an option responding to the consumer demand for new flavors with added nutritional value, better sensory characteristics, and more striking colors ^[47][48][68,69].

The consumer demand for fruit juices is growing as they are a naturally rich source of bioactive compounds, however, their susceptibility to spoilage limits the shelf-life ^[49][70]. For this reason, the food industry is constantly searching for new processing technologies to extend the shelf life with a low impact on the fruit juice quality, as the consumers are now more conscious of health and diet ^[50][51][71,72]. To extend the shelf life of fruit juices, the most commonly used preservation process is thermal processing (pasteurization and sterilization). For example, apple juice is treated by HTST at 77 to 88 °C for 25 to 30 s ^[52][73] and orange juice by HTST at 90 to 95 °C for 15 to 30 s ^[53][74]. However, this process may promote undesirable quality changes in the juice composition and the sensory and nutritional values of the fruit juice ^[54][75].

For example, Vegara et al. ^[55][76] evaluated the influence of pomegranate juice pasteurized on anthocyanin stability and verified that the application of thermal treatments (65 and 90 °C for 30 or 5 s) diminished the percentage of anthocyanins in the polymeric form but increased the monomeric anthocyanins. Also, Aguilar-Rosas et al. ^[56][77] studied the high-temperature short time (HTST) pasteurization process (90 °C; 30 s) of apple juice and observed a decrease in the concentration of the total phenolic compounds (~32%), compared to the untreated juice.

Mena et al. ^[57][78] analyzed pomegranate juice before and after low-, mild- and high-temperature pasteurization (LTP, MTP, HTP, at 65, 80, and 95 °C, respectively, for periods of 30 or 60 s, and observed that the total anthocyanin concentration was different among thermally processed and untreated pomegranate juices, the lowest concentration being determinate in the control (untreated pomegranate juices), while the highest concentration of anthocyanins was found in the juice treated at 95 °C for 30 s.

Consequently, as consumers want fruit juices not only with extended shelf life but also with enhanced quality characteristics, researchers are looking for innovative non-conventional technologies such as high-pressure (HP), ultrasound (US), pulsed electric fields (PEF), ultraviolet-C radiation (UV-C), low-pressure plasma (LPP) and Ohmic heating (OH) (Table 2) to achieve the consumer demand for fruit juice with an extended shelf life, better quality, and an improved nutritional profile ^[51][72]. Recent studies reported a positive impact of non-thermal processing on juice quality ^[58][59][79,80]. Optimized non-thermal processing enhanced the content of the bioactive compounds in fruit juices and consequently their beneficial health effects ^[51][60][72,81].

For example, Linhares et al. ^[83][82] compared the composition, stability, and bioactive compounds of juices produced with different processing technologies, thermal technologies such as high-temperature short time (HTST), ultrahigh temperature (UHT), and non-thermal technologies such as high power ultrasound (US), UV-pulsed-light and low-pressure plasma (LPP). These authors showed that all the juices produced with non-thermal processes increased the sugar content (glucose and fructose), and the amino acid betaine, except for the juices produced by the combination of the ultrasound process followed by low-pressure plasma (US.LPP). On the other hand, the juices produced by HTST and UHT showed higher concentrations of fatty acids and phenolic compounds.

Another example of non-thermal technology is the application of high-pressure (HP) and high hydrostatic pressure (HHP) processing on acid fruit juices. This technology is effective in the inactivation of microorganisms (meeting the Food and Drug Administration requirement of a 5-log reduction) and denaturation of diverse enzymes ^[84][85], without loss of vitamins, pigments, and compounds related to sensory characteristics ^[85][86]. High-pressure (HP) processing is preferred to thermal processes in terms of holding phenolic compounds. HP and HHP treatment at moderate temperature is described to have an insignificant effect on the anthocyanin concentration of diverse red fruit juices, as well as the flavor, taste, and color changes being minimal ^[86][87]. However, these authors also showed that the bioactive content of red fruit reduced with the intensity of the treatment in terms of processing time and pressure level. Varela-Santos et al. ^[87][88] evaluate the effect of HHP processing (350–550 MPa for 30, 90, and 150 s) on the concentration of anthocyanins, phenolic compounds, and color of pomegranate juice during 35 days of storage at 4 °C. These authors showed that HHP juice processing has a perceptible effect on the total color difference (ΔE) between untreated and treated samples, and the highest color difference was observed at day 35 of storage for 550 MPa during the 90 s. These results showed clearly that the color stability of pomegranate juice is dependent on the processing conditions. Orange juice showed an increase in flavanone after HPP processing (400 MPa, 40 °C, 1 min), compared to the untreated juice ^[54][75]. Also, Sánchez-Moreno et al. ^[88][89] and Oms-Oliu et al. ^[89][90] observed in orange juice treated with HP (400 MPa/40 °C/1 min) an enhancement in the concentration of naringenin by 20% and the concentration of hesperetin by 40%, compared with the untreated orange juice and the preservation of the orange juice sensory characteristics.

In addition, pulsed electrical field (PEF) processing, which applies short bursts of high voltage electricity for microorganism inactivation, has been successful in a variety of liquid products with relatively low viscosity and electrical conductivity such as orange juice and cranberry juice ^[90][91]. PEF has a high potential for microorganism inactivation and enzyme denaturation, extending the shelf life and preserving the nutritional, vitamin, aroma, and sensory characteristics due to the very short processing time and low processing temperature. Blueberry juice processed by HP (600 MPa/42 °C/5 min) and processed by PEF (36 kV/cm, 100 μs) stored refrigerated at 4 °C for 56 days, showed a 50% of ascorbic acid reduction in both unprocessed blueberry juices and in the PEF-treated juices at the end of the refrigeration time. However, HPP-treated blueberry juice better maintained the ascorbic acid content during the storage time with a reduction of 31%, and the anthocyanins in the blueberry juice treated with HP were also better preserved. Sánchez-Moreno et al. ^[88][89] considered that the PEF treatment did not modify flavanone content, but in general, the pasteurization process led to a diminished naringenin content (16.04%), with no modification in hesperetin. They also observed that even though the losses in total vitamin C were <9%, treatments with the higher temperatures (HPT) (90 °C/1 min), tend to show a greater reduction in the concentration of both forms of vitamin C. HP treatment (400 MPa/40 °C/1 min) led to an increase in carotenoid release (53.88%) and vitamin A value (38.74%). PEF treatment did not modify individual or total carotenoid content. Traditional thermal treatments did not have any effect on the total carotenoid content or on the vitamin A value. In apple juice, the treatment with PEF decreased the concentration of total phenolic compounds (~15%) compared to the untreated juice, however, this decrease was lower than that observed with thermal pasteurization, which decreased the phenolic compounds by 32% ^[56][77]. In summary, according to Sánchez-Moreno et al. ^[88][89], HP and PEF technologies were more effective than HPT treatment in preserving the bioactive compounds of orange juice. Likewise, Agcam et al. ^[91][92] showed that the total phenolic concentration of orange juice was enhanced after the PEF and thermal pasteurization treatments. Orange juice processed by PEF contained higher phenolic compound concentrations than those processed by the heat. The orange juice treated with PEF had more stable flavonoids and phenolic acids than those treated with thermal pasteurization. The PEF-treated samples had higher sensory scores than the heat-treated samples. Therefore, these authors suggested that the application of PEF processing to orange juice seems to be a promising alternative to thermal pasteurization to obtain an extended shelf life and better preservation of phenolic compounds and should be taken into consideration for industrial-scale production.

In recent times, cold plasma was considered suitable for use with fruit juices ^[92][93][93,94]. Therefore, cold plasma is accepted as a potential, novel, non-thermal technology for the quality improvement of fruit juices, and numerous research works have studied the application of cold plasma in fruit juices ^{[60][78][94][95][96][97]}[1,81,95,96,97,98]. The treatment is performed under milder temperatures (< 70 °C), which contributes to the preservation of sensory characteristics and the maintenance of bioactive compounds in fruit juices ^[77][99]. Bursać Kovačević et al. ^[78][96], using a cold atmospheric gas-phase plasma in pomegranate juice, observed an increase in the concentration of anthocyanin between 21% and 35% compared to the untreated juice, which confirms that the cold plasma has a positive impact on anthocyanin stability. More recently, de Castro et al. ^[60][81] studied the application of cold plasma excitation frequency (200, 420, 583, 698, and 960 Hz) in the juice physicochemical properties. These authors concluded that after the application of this non-thermal treatment the content of ascorbic acid was increased by increasing the plasma excitation frequency. According to these authors, cold plasma application could be an interesting method to enhance the nutritional quality of fruit juices. It was also observed in diverse fruit juices, for example, strawberry juice, blackcurrant juice, and raspberry juice, that anthocyanins are stable to HP treatments, such as the application of cold plasma excitation frequency ^[58][59][79,80].

Several research works have been conducted on different fruit juices using ohmic heating which is also known as electrical resistance heating, such as the inactivation of microorganisms ^{[98][99][100]}[100,101,102] and enzymes, for example, pectin methylesterase (EC.3.1.1.11) also called pectinesterase ^[61][101][103,104] and polyphenoloxidase, for minimizing enzymatic browning ^[81][105]. In orange juice treated with ohmic heating around 96% of the pectin methylesterase activity was reduced as observed by Demirdöven et al. ^[61][103]. In fruit juices, the use of ohmic heating to inactivate enzymes does not affect the juice flavor ^[102][106]. Hashemi et al. ^[103][107] compared different ohmic heating treatments (150, 200, and 250 V; 120 s; 99.4 °C) with the conventional heating process (90 °C; 15 min) for the inactivation of microorganisms in blended citrus juice (sweet lemon and orange). These researchers showed that the inactivation rate of pathogenic bacteria using ohmic heating increased by the increase of voltage from 150 to 250 V. Also, Darvishi et al. ^[104][108] studied the influence of ohmic heating on the concentration of black mulberry juice in comparison to the traditional heating treatment. Using ohmic heating the phenolic concentration of the juice was 3–4.5 times greater than if using traditional heating treatment.