5 Ready-To-Use Minimal Preservation Technologies for Fruit, Vegetable and Nut Based Cold Pressed Juices
There is a big buzz about the benefits of cold pressed fruit and vegetable juices and nut based beverages. The premium cold-pressed industry has been valued at an estimated $3.4 billion and is expected to experience a strong growth in the next seven years around the world.
Cold pressing is a method of processing raw ingredients by first crushing fruits, vegetables or leafy greens before pressing out the juice. In order to maintain fresh-like attributes of juice, cold pressing is typically done at refrigerated temperatures and minimum exposure to oxygen. The known fact is that cold pressed fruit and vegetable juice products are an essential source of vitamins, antioxidants, enzymes and proteins, but only when minimally processed. The product labels often include terms such as fresh, natural, no added preservatives, raw, organic, vegan, and cleansing beverages.
However, cold pressed products can stay fresh only for 72 hours. Thermal pasteurization is an effective preservation technique for extending shelf life of juices, but often negatively impacts both nutritional and quality parameters as well as fresh-like flavour. Ideally, minimal preservation technologies such as mild heat or non-thermal methods are expected to be used to retain the fresh characteristics and flavor with extended refrigerated shelf-life of this type of product. That is why another buzzword often used with cold pressing is high pressure processing, or HPP. Despite the commercial success of HPP, there are other minimal processing techniques that have a potential for preservation of fresh juice products.
1) High Hydrostatic Pressure (HPP) processing of bottled juice, typically at 600 MPa for 3 to 5 min, is effective against common pathogenic and spoilage organisms and capable of extending shelf-life up to 45 days in refrigerated conditions. Juice manufacturers have to comply with the US FDA Juice HACCP. Health Canada also approved HPP as a part of Novel Food regulations for fruit and vegetables smoothies and juices. However, HPP is associated with high start-up and operational costs of batch processing while also requiring a large amount of space and use of plastic packaging.
2) Ultraviolet (UV-C) light is approved by the US FDA for treatment of juice products to reduce human pathogens and other microorganisms. The light source must consist of low pressure mercury lamps with 90% of the emission at a wavelength of 253.7 nm and juice flow pattern must meet turbulent flow. Health Canada also issued no-objections novel foods decision on the use of UV-C for apple juice/cider treatment. UV light technology is a less expensive continuous process that is effective against all food borne pathogens, parasites, natural microflora, molds and yeasts, and extends shelf-life of juices while using various types of glass and metal packaging. To improve efficacy of UV-C processing, UV-C treatment can be combined with moderate temperatures. A few UV-C units are available commercially that are based on employing thin-film turbulent flow or Dean flow in the coiled tube.
3) Pulsed Electric Fields (PEF) technology enables a shelf life increase by permeabilizing cell membranes of microorganisms, retaining high product quality and freshness in juice. The technique can be applied continuously and hardly needs a residence time. For preservation of juices, field strength of 10-20 kV/cm and energy delivery of 50-120 kJ/kg is the appropriate processing condition. Lack of reliable and affordable industrial size equipment and a lack of innovation have limited the industrial exploitations in the past. Recently, new PEF-based equipment was developed and commercialized in the EU. Successful implications of the PEF technology will require the identification of a cost or quality benefit to justify the costs of investment. PEF has no objections from the US FDA for treatment of juices under specified conditions provided by PurePulse technologies. Being continuously operable, the technique allows flexibility with regard to processing capacity as well as bottling into various packaging formats and materials.
4) Ultra High Pressure Homogenization (UHPH) is based on principles of conventional homogenizers and developments in
valve design and materials that have enabled pressures of 400 MPa to be achieved. UHPH is a purely mechanical process, which is evoked by forcing a fluid product through a narrow gap under high pressure. In contrast to HPP, UHPH is also called “dynamic” high pressure assisted processing of liquids. The benefits of UHPH include shelf-life extension through inactivation of microorganisms and improvements in functionality due to increased emulsion capacity and stability, with minimal effects on nutritional value and sensory characteristics. In combination with temperature, inactivation of spores such as Bacillus amyloliquefaciens can be achieved. Also, UHPH can be successfully applied for popular nut-based dairy beverages.
5) High Pressure Carbon Dioxide (HPCD) or Dense Phase Carbon Dioxide (CO2) DPCD process is the non-thermal technology that uses pressurized CO2 in the liquid, gaseous or supercritical fluid states at pressure up to 10 MPa. The advantages of using DPCD for juices include mild temperature ranges (30-50oC) and much lower pressures that are approximately 1/10th of the required pressures for HPP. This allows retention of juice quality attributes, nutrients and other beneficial components such as anthocyanins and polyphenols. Carbon dioxide is an inexpensive gas in industrial quantities and is an accepted ingredient in foods and beverages. Exclusion of oxygen is beneficial in reducing oxidation reactions. Additionally, the reduction of pH by dissolved CO2 may be beneficial in reducing microorganisms, inactivating enzymes, and preserving nutrients such as vitamin C. The operation can be continuous. The main disadvantages are that DPCD process is not used commercially despite the fact that it meets juice HACCP requirements in the USA under the trademark of Better Than Fresh. There is no continuous commercial equipment with the throughput of the existing thermal treatment equipment. Compared to high-volume thermal pasteurization, DPCD is more expensive and requires specialized high-pressure equipment.
The applications of these technologies will expand when their advantages will be validated and demonstrated commercially. They are very much dependent on the cost, design and availability of industrial equipment for small and medium size producers. More research is needed to explore physical, enzymatic and microbial stability of juice suspension, as well as optimization of juice formulation, and pre and post processing operations.
About The Author
Dr. Tatiana Koutchma is a Research Scientist at Agriculture and Agri-Food Canada, focusing
on applied research related to novel processing technologies, development and validation of
new processes for industry. She is an internationally recognized expert in high pressure,
ultraviolet light, and other advanced thermal and non-thermal methods.