High Quality Food
Consumer awareness and increased availability of food assortment make natural and healthy food a permanent element of the diet. The trend of pro-health food is becoming popular, which results in the emergence of more products with high quality and nutritional value. Particularly, the high quality beverages including the freshly squeezed juices increasingly are appearing on store shelves.
Negative Impact of Heating
The problem in the beverage industry is the short shelf life of the products and the sensitivity of nutrients. This fact makes distribution more difficult. Juice after only a few hours are not suitable for consumption. This situation exposes producers to losses. As a result, the manufacturers use thermal processes, such as high pasteurization to extend the shelf life. Unfortunately, this action often causes a changes of the food quality. The nutrients lost from fruits and vegetables must be replenished, often from not natural sources.The high temperature has a negative impact on the nutritional value, but also for flavor compounds. The producers declare that their products consists only of natural and fresh raw materials, with no added sugar. However, the taste of the product often differs from fresh fruit and vegetables.
High Pressure Processing of Beverages
The juices subjected of HPP process using the parameters relevant to a given assortment are characterized by extension of the shelf-life even up to 3 months in refrigeration conditions. The pressure range used in practice in the beverage industry is usually 400-600 MPa. Suitable adjustment of parameters allows to perform the process in the highest efficiency.
HPP allows the preservation of healthy properties of juices, smoothies and plant beverages, such as nut or oat milk. The specificity of HPP is due to the fact that the high pressure only causes a changes in high molecular compounds. Smaller substances, such as vitamins, natural colors or flavors remain intact. The technology consists in limiting the use of high temperature during the process, which is its biggest advantage. The nutritional value and natural taste of the products are comparable with fresh raw materials.
HPP is packaged food processing technology. The high water content of liquid products like juices makes the hydrostatic pressure moves uniformly in all directions and does not generate cutting forces. It protects the product against crushing. Unlike heat treatment, the pressure, acts immediately in the entire volume of the food product, regardless of its size and geometry. The packaging should have appropriate flexibility and barrier properties. A popular form of packaging used in HPP are plactic bottles. Most of the beverages on the market are packaged in this way.
High pressure treatment is the particularly advantageous method of processing of acidic food. Most juices are included in this group of products. High pressure causes the degradation of pathogenic and spoilage microorganisms. The high water content and the beneficial pH of the products strengthen the effect of treatment. The process causes a number of changes in the microbes cells. The acidic environment prevents from reconstructions of the cells damaged by high pressure and enhances the germicidal effect of the HPP. Low pH level of juices and beverages can also inhibit the germination of pathogen spores .
Figure 1. Reduction of E.coli O157:H7, Salmonella and L. monocytogenes in artificially inoculated high acid products (pH<4.6) immediately after HPP treatment and after one day of storage at 4 ºC 
Figure 2. Reduction of E.coli O157:H7, Salmonella and L. monocytogenes in artificially inoculated low acid products (pH>4.6) immediately after HPP treatment and after one day of storage at 4 ºC 
The figures above show the level of reduction of the pathogenic microorganisms in high and low acidity juices after HPP. Analyzes were conducted immediately after the process and the following day. It was found that a higher level of microbial reduction (5-log reduction) was achieved for higher acidity apple juice and vegetable juice (green juice). In the case of carrot juice with the highest level of pH, this effect was achieved only in the degradation of L. monocytogenes. The test results illustrate the positive effect of the acidic environment on the enhancement of the germicidal effect of the high-pressure processing .
On the market the most juices have a low pH level. A product acidity is very important in optimizing HPP processes. The low pH level of juices allows for using of lower process parameters, which is directly related to the reduction of processing costs. HPP is a particularly effective method to obtaining safe food products with acidic pH.
High Pressure for High Safety
Juices are products particularly susceptible to spoilage. The manufacturers use the pasteurization to extend the shelf life and facilitate distribution of products. The high temperature treatment causes the destruction of bacterial cells as well as yeast and mold, allowing to the extension of the shelf life of products. The preserved by food can be stored without cooling conditions. Nonetheless, consumers increasingly do not trust this type of product. It is hardly surprising. A fruity product that is fresh for several months outside of the refrigerator may arouse suspicion.
High pressure processing is considered a natural process. It does not interfere with the product, as traditional methods like pasteurisation or sterilization. In addition, high water content and appropriate pH strengthen the effect of HPP. The influence of high-pressure treatment on the number of microorganisms in freshly squeezed apple and orange juices subjected to HPP is presented below. The high-pressure process was carried out in the EXDIN Solutions equipment - HPP 6-CAL70 model.
Figure 3. The effect of high pressure processing on degradation of the total viable count and yeasts and molds in orange and apple juices 
It was observed that HPP significantly influenced the level of microorganisms in the both analyzed juices. It was found that HPP treatment at 400 MPa/3 minutes significantly reduced the total viable count and the number of yeast and mold. After applying these process parameters, the number of yeast and mold in both juices was below that recommended by Stannard et al.  limit (103 CFU/ml). The opposed results was obtained for raw juices. It was observed that treatment at 500 MPa practically complete reducted the microorganisms occurs in the both juices, which directly affected the extension of the shelf-life. The reduction of the total viable count, as well as yeasts and moulds was increasing with the increase of the pressure level in the both juices. These results illustrate the high effectiveness of the high pressure treatment in degradation of the spoilage microorganisms.
High Nutritional Value
Despite the dynamic development of new products in the food industry a juices are still the most popular source of nutritiens in our diet. The industry of the NFC juices (not from concentrate) has never been at the good position as it is now. Cold pressed juices are a great source of vitamins and antioxidants necessary for the proper functioning of the body. Cold pressed juices are classified as premium products, distinguished by a particularly high content of biologically active ingredients. The innovative cold juicing technology counteracts the loss of their valuable ingredients through low pressure on fruits and vegetables. The consturction of the equipment minimalizes the metal parts which can affect oxidation of the ingredients and contribute to the rapid loss of quality of juices.
Natural and healthy food is becoming extremely popular on the market. Consumers reading a product labels are becoming more and more often seen in supermarkets. The demand for healthy food is increasing and the consumers are becoming more aware and demanding. They are looking for minimally processed products without an endless list of substances. Natural food is trendy, so producers are intensive looking for production methods which do not affect the nutritional value and taste of food.
Vitamins Do Not Like a Heat
Vitamins and more diffrent bioactive compounds, e.g. antioxidants having a positive effect on health are characterized by low resistance to high temperatures. The pasteurizated product loses the valuable properties. Most of research proved it. High temperature negatively affects the vitamins and the functional compounds as well as flavor of treated beverages. In addition, the natural color of the juices is changed, because the food colors such as β-carotene or anthocyanins are thermolabile. The substances do not resistant to high temperatures.
losses of bioactive compounds, e.g. vitamins, antioxidants
reduction of natural taste and aroma
natural color changes
HPP used instead of pasteurization allows preserve the functional components and the natural taste of fruits and vegetables in juices. The high pressured juices and beverages do not have the cooking flavour. The taste significantly differs from thermally preserved juices. Modern HPP technology prevents the degradation of vitamins and nutrients.
One of the most popular antioxidant compound is vitamin C. It has scientifically proven the positive effect of human health. The vitamin C is water-soluble, easy oxidized and not resistant to high temperatures. During technological processes a products are often subjected to the thermal treatments. The consequence of this treatment is the degradation of the ascorbic acid. An additional disadvantage of the thermal processing of juices are the losses of the natural taste of fruits and other vitamins and antioxidants.
HPP technology is innovative solution to protect the vitamin C in beverages. High pressure unlike to high temperature do not causes the degradation of the ascorbic acid. HPP does not affect the chemical bonds in its structure. The figure 4 shows the results of test the vitamin C content in the freshly squeezed orange juice after HPP treatment during 14 days of refrigerated storage. The research was carried out on the orange juices due to the fact that it is a common source of the vitamin C in the human diet. The high-pressure process was carried out in the EXDIN Solutions equipment - HPP 6-CAL70 model.
Figure 4. The effect of HPP on the content of vitamin C during the 14 days of refrigerated storage 
The main factor of HPP treatment is not the temperature, but pressure. The high pressure processing did not cause significant changes in the content of vitamin C in orange juices. The level of the substance remained virtually unchanged throughout the storage period. The juices were still characterized by its high content and the natural flavor of the oranges. It was found that the vitamin level was comparable with fresh-squeezed juice.
The EXDIN Solutions application allows to obtain a microbiologically safe product that retains its best nutritious and flavored qualities. The EXDIN equipment construction increases productivity due to multi-cylinder system, which directly affects the efficient use of the equipment and to achieve the required effects.
Figure 5. The effect of HPP treatment on nutrient content (vitamin C) of apple juice 
Kim et al.  presented the results of their research on the influence of thermal treatment (pasteurisation) and high pressure processing on the content of vitamin C in apple juice. The HPP treatment at 500MPa/3min/25°C did not significantly change the content of the vitamin C, while pasteurization at 85°C/1min contributed to significant degradation of the compound. The high pressure procesing positively influenced the stability of the vitamin C in the juice. The juices treated at high pressure and the raw juices were characterized by a similar content of the vitamin. HPP effective increase the nutritional value of products .
Figure 6. Values of ascorbic acid in HPP blueberry juice treated at 200, 400 and 600 MPa 
HPP controls the content of nutrients in juices. In contrast to pasteurization, high-pressure treatment allows for the protection of the sensitive vitamin C. Despite the fact that level of pressure is 6 times highest than in the Mariana Trench the process does not significantly affect on the ascorbic acid. It shown in the analysis by Barba et al. . The researchers proved that the ascorbic acid was stable in the blueberry juice after pressure treatment at the range from 200 to 600 MPa. It has been preserved in more than 92% of the initial content. The pressure level used in industrial practice is 200-400 MPa. The study present the treatment with higher pressure levels then industrial processing, which inform that even higer parameters in treatment gives satisfactory results .
Polyphenols are the next juices compounds with special healthy value. It is a group of several thousand compounds and biologically active substances present in fruits and vegetables. Similar to the vitamin C these compounds are powerful antioxidants. The phenolic compounds counteract the formation of cancer cells and have antioxidant potential even 30 times stronger than the ascorbic acid. However, their resistance to high temperature conditions is similar to the vitamin C. Thermal processes degradate of the polyphenols as effectively as they remove bacteria from a product. The nutritional value of the pasteurised products decreases, along with the valuable properties of the polyphenolic compounds.
Figure 7. The effect of HPP of the total phenoilic content in apple juice during 14 days of refrigerated storage 
The Figure 7 presents the influence of high hydrostatic pressure on the total polyphenol content in the apple juice. The analysis showed that there was no significant effect of the treatment on the polyphenol content in juices for 14 days after production. It is worth adding that the amount of the antioxidants tested was comparable to the content of the polyphenols in the raw juice. After HPP process the content of polyphenols was higher immediately. It was found that increased substances concentration in beverages may be due to the increased extensiveness of polyphenolic compounds after the high-pressure treatment. This information is important because HPP is the process that allows to obtain a product identical with the unprocessed. In this case, even with the increased pro-health value in comparison with the raw juice.
Figure 8. Values of total phenolic content in HPP blueberry juice treated at 200, 400 and 600 MPa 
Barbra et al.  proved that regardless of the level of used process parameters the high pressure treatment has great potential to obtaining a high-value foods. The blueberry juice polyphenols was resistant to all the applied pressure levels and processing times, which resulted their stability in the product. Antioxidant substances have an increased susceptibility to extraction after high pressure treatment. It often results their increasing in a juices after the process. HPP is the innovative method that instead of causing loss, increases availability of vitamins and antioxidants in fresh juices and beverages .
Taste and smell, the main product features affecting consumer acceptance
Pasteurization affects the natural sensory qualities of juices and beverages. The aromatic bouquet of fruits and vegetables after heat treatment turns into the cooking aroma. The traditional thermal processing not guarantees preserving these features, but high pressure processing. Due to the limited impact of the HPP process on aromatic compounds the juices are characterized by the taste and smell of fresh fruits and vegetables. High pressure effectively destruct the spoilage microorganism and this makes the product is safe throughout of the shelf life.
Figure 9. Sensory evaluation of control and high pressure treated grape juice during refrigerated storage (1 or 60 days at 4°C) 
The raw and high pressure treated grape juices were subjected to sensory analysis under suitably prepared conditions. There were no significant differences between the control and the HPP samples. There were no sensory changes in 1 day of storage. The both samples were characterized by freshness, a similar aroma and a sweet feeling. After 60 days, the changes were felt in the control sample of the juice. The level of perceptible sweetness was much lower. It was found the fermentation process, which was caused by microbiological growth. HPP sample had the stable acidity level, demonstrating the absence of fermentation processes. The HPP juice was not characterized by the taste of cooked fruits.
The grass aroma was less noticeable in the HPP sample than the raw juice. There were no significant sweetness changes in in HPP juice, in contrast to the raw juice. After 30 days the sweetness in control sample decreased.
The HPP grape juice was general acceptaced among the evaluators. High pressure processing combined with refrigerated storage is an effective way to extend the shelf life of juices and beverages, while minimizing nutrient losses and sensory characteristics .
Table 1. The HPP impact on the color of the blueberry juice treated at diffrent levels of pressure 
1. Legumes beverages, e.g. soybean milk
Common source of protein for lactose intolerant people. Soybean as one of the main raw materials for the production of plant milk substitutes is characterized by a high content of protein, essential fatty acids and isoflavones. Soy beverages a positive effect on the cardiovascular system and to effectively counteract the formation of cancer cells.
2. Cereal beverages, e.g. oat, rice, barley
In Europe, oat milk is one of the most common plant-based alternative to cow's milk. Oats are very popular due to the presence of dietary fiber, phytochemicals and high nutritional value. In addition to the beneficial amino acid profile, oat milk contain ß-glucan, B-vitamins and iron. Unlike nut-based beverages, oat milk is free of allergens. It have a high starch content. Oat milk begin to gel, which reduces the quality of the product.
3. Nut beverages, e.g. almond, coconut, hazelnut
Nuts are an excellent source of valuable proteins and high-quality fats. Their vitamins and minerals make the beverages are extremely popular, also due to the presence of anti-cancer antioxidants. Fat-soluble vitamins are accompanied by the necessary unsaturated fatty acids. Almond milks, which are the most popular products of this type in the USA, are a rich source of minerals such as magnesium, calcium, zinc and phosphorus. Coconut plays a major role in Southeast Asia, where coconut water and coconut milks are produced on a large scale.
4. Seed-based beverages, e.g. hemp, sesame, flax seeds
Oilseeds are considered to have equally high potential as a raw material for the production of plant-based milks. Beverages based on sesame, flax or hemp seeds are becoming extremely popular due to the high concentration of nutrients in the seeds and their functional properties.
5. Pseudocereal bevarages, e.g. buckwheat, quinoa milks
Thermal operations, are subjected to an plant-based milks cause less or larger changes in the product. Heat treatment, such as pasteurization and sterilization, can cause changes in food ingredients, especially proteins and lipids, which stabilize the emulsion. Thermal processes affect increased dissociation, denaturation and aggregation of proteins, which negatively affects their solubility in beverages. Also, heating of starch causes a significant increase in viscosity, which can affect the stability of the product. The food industry is looking for methods to limit the use of high temperature in the production process to minimize the impact of thermal processes on the properties of plant-based milks.
High Pressure Processing of Plant-Based Milks
The use of HPP technology in preserving the plant-based milks allows to reduce the pathogenic and spolage microorganisms while protecting the product against adverse changes caused by traditional thermall methods. For example, a soy based drink is a low acidity product. The high pH level allows bacteria to grow faster and makes it prone to spoilage. The use of UHT or pasteurization to increase safety carries the risk of losing the unique taste and aroma values of drinks and their nutritional value. High temperatures negatively affect their content, because these compounds are not resistant to thermal treatment. Additionally, changes occur properties of beverages, such as gelation of the starch and denaturation of the proteins, as a result desired by the gel and the formation of sediment in the product.
Plant-based milks during high temperature processing are also exposed to changes in color and sensory characteristics caused by Mailard reactions. Preservation is becoming a problematic issue for the producer, because pasteurization exposes the product to loss of quality. High quality is extremely appreciated by the consumer. Unfortunately, the non-treated product is unfit for consumption after a few days.
High Pressure Processing
Alternative products, alternative solutions
Plant-based milks preserved by HPP are characterized by a high content of nutrients and minerals, because high pressure does not adversely affect the nutritional value of the product. Quality control and food safety, which are key elements in food production, are facilitated by the use of high hydrostatic pressure. This makes it possible to obtain several times extended shelf life, and the producer does not have to worry about the quality loss of the product. HPP technology minimizes the negative effects of high temperatures, because pressure is a food-preserving factor.
Figure 10. Log reduction of E.coli O157:H7, Salmonella and L. monocytogenes in artificially inoculated plant-based beverages immediately after HPP treatment and after one day of storage at 4 ºC 
High pressure treatment resulted in high reduction of pathogenic microorganisms in coconut water and almond milk. In order to obtain the appropriate number of pathogens, inoculation of products with E.coli, Salmonella and L.monocytogenes cells was used, and then stored at 4ºC until HPP. The samples were pressurized. High pressure processing enables the degradation of microorganisms above 5 logarithmic levels, which is a highly satisfactory result and allows obtaining a microbiologically safe product.
Pressure transfer medium in the process is water. Its high content in beverages makes HPP technology highly effective due to the even spreading of pressure in the product. In addition, high-pressure treatment minimizes the impact on the product texture. The packaging after the process is intact even to the slightest extent.
The HPP Advantages:
- Extending the shelf life without negative affecting the product
- Increased safety and elimination of microbiological hazards
- Preservation of natural flavors
- Clean label
- High nutritional value, without preservatives and artificial additives
- Innovative products with high quality
- Facilitated distribution and guaranteed market effect
The high pressure processing of juice and beverage allows for more beneficial effects of treatment than during pasteurization. The product is microbiologically safe and stable throughout the storage period and does not lose nutritional value and sensory characteristics, as in the pasteurized juices.
HPP is a highly effective way to extend the shelf-life of products that are prone to easy spoilage. Increased microbiological safety gives the manufacturer a competitive advantage, as it can increase the distribution range without adversely affecting the product.
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