# The Influence of Processing on the Bioactive Compounds of Small Berries
## 4 Processing of Small Berries and Their Effects on Bioactive Compounds
### Pasteurization  
Pasteurization is an essential process applied in the food industry to assure the microbial stability of berry products such as juices, jams, pures, or stewed berries for a specific period. Often, food products with low acidity are sterilized (>100 \({}^{\circ}\)C), while those with high acid are pasteurized (<100 \({}^{\circ}\)C) [87]. For fruit juice processors, the thermal processing conditions applied must achieve a 5-log reduction in the most resistant pathogens present in the final product [88]. On the other hand, the heat treatment applied has a strong impact on the phytochemical composition of the berry products. Products treated by thermal pasteurization have an enhanced quality compared to thermally sterilized products, as the applied process parameters are less severe. The pasteurization treatment can be performed by using thermal and non-thermal technologies or a combination of them (Figure 4). Conventional thermal pasteurization is one of the most cost-effective technologies used at the industrial level to ensure the shelf life of juices, as it possesses good bactericidal and enzyme inactivation effects. The high temperatures and long exposure time reduce the quality of the juices from sensorial, nutritional, and functional perspectives [58]. The phytochemical content is also influenced by pH and the presence of oxygen and other components present in the berry products. Most conventional thermal technologies cause a reduction in the bioactive compounds present in berry products. The thermal pasteurization (92 \({}^{\circ}\)C, 15 min) of strawberry puree decreased the anthocyanin content by about 43% compared to the control sample [89]. On the other hand, the pasteurization of blackberry and raspberry juices did not exert a significant reduction in the total anthocyanin and total polyphenol contents when compared to non-pasteurized juice [90; 91]. Ohmic heating and MW heating are considered promising alternatives to the conventional thermal pasteurization of berry products. MW heating is the result of the interaction between electromagnetic radiation and dielectric materials at 915 MHz and 2450 MHz (frequencies approved for use in the food industry) [87]. In ohmic heating, the electrical current passes through liquid/semi-solid samples, promoting a temperature increase, at levels depending on electrical conductivity, particle size, ionic concentration, or field strength. In addition, pasteurization is faster and more effective when using ohmic and MW heating than conventional pasteurization [87]. However, their application on a large scale is limited by their high initial costs and negative effects related to the high temperature and electrochemical reactions [58]. Non-thermal technologies based on high-pressure processing, US, PEF, or irradiation have emerged in recent decades and can be used to complement or replace conventional thermal pasteurization. In addition, the low processing temperature applied by these technologies causes limited effects on small constituents like vitamins or antioxidants, enabling the development of high-quality products. High-pressure treatments can be divided into hydrodynamic treatments (high-pressure homogenization--HH) and hydrostatic treatments (high hydrostatic pressure--HH) [92]. Pressure between 200 and 400 MPa, applied for up to 15 min, improved the phenolic and anthocyanin contents of blueberry juice due to the higher extractability of the constituents with antioxidant properties following pressurization [93]. [PERSON] et al. [94] found that HHP treatment of mulberry juice at 400 MPa for 5 min ensured the retention of over 80% of the anthocyanin content of the fruits. HPH allowed the total phenolic content of strawberry juice to be increased when applying pressures of at least 100 MPa [95]. Combined with conventional thermal pasteurization, high-pressure treatments showed excellent results in preserving the nutritional, sensorial, and functional properties of berry products, as reported by [PERSON] et al. [96] for mulberry juice.