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Application of power ultrasound in the food processing industry

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The power of the ultrasound wave…

Power ultrasound is considered today as an emerging and promising technology in the food industry. The potential of this technology in both solid-liquid systems and solid-gas systems has aroused wide interest due to its ability to accelerate mass transfer processes. Additionally, the benefits of the application of power ultrasound, alone or in combination with thermal, light or high-pressure treatments, in the inactivation of microorganisms and enzymes for the preservation of foods have been widely demonstrated in the food technology area. [1]

Ultrasound, is an elastic wave that travels through a conductive medium producing compression (high pressure) and rarefaction (low pressure) and whose frequency exceeds that of the sound audible by the human ear (20 kHz). Like sound, ultrasound is transmitted through any solid, liquid or gas that possesses elastic properties. Depending on its application, ultrasound can be classified into high power (low frequency) or low power (high frequency) ultrasound. Low frequency (20kHz-100kHz) ultrasound is used for the Intensification of the transport phenomena and it is characterized by causing changes in the physical, chemical and/or biochemical properties of the media in which it is applied; and high frequency (> 100 kHz) ultrasound is used as a non-invasive technique for the analysis and evaluation of product quality. [2]

Food processing is constantly evolving due to different challenges and changes in the preferences and needs of consumers. These changes respond the need to produce healthy, sustainable, safe, additive-free and better-quality food. In reaction to this demand, the intensification of food processes has emerged and has become an area of growing interest within the food industry. Lately, the use of ultrasound in food industry covers different purposes including analysis methods and food processing such as freezing, cutting, drying, tempering, homogenization, degassing, antifoaming, filtration and extraction. There may be numerous advantages of using ultrasound during food processing such as effective mixing, increment of mass transfer, reduction of energy consumption and product temperature and increment of product yield. Due to the elimination of microorganisms and enzymes without destroying nutrients of foods, ultrasound can be used as an alternative method to thermal treatments in food preservation. Low power ultrasound is thought to be an attractive non-thermal method due to overcome problems which occur during heat treatments such as physical and chemical changes, nutritional loss and change in organoleptic properties. [3]

Furthermore, the current structure of agro-industrial and food processing industries also contributes to the generation of by-products/waste streams. To improve sustainability and reduce waste, it is essential to have a comprehensive understanding of the various sources of residual biomasses and to apply new, economically feasible technologies able to extract valuable compounds and breathe new life into waste. Additionally, in the path to tackle the residual streams disposal from food and beverages processing by enhancing their valorization and re-circulation into the process, ultrasound-assisted extraction (UAE) has been proved to be a promising technique. UAE is an inexpensive and efficient alternative to conventional solid-liquid extraction techniques, which main advantages includes better penetration of the solvent into cellular material, enhancement of the mass transfer due to the cavitation effect that provokes the disruption of the plant cell walls and facilitates the release of extractable compounds, reproducibility of the results and the reduction and the use of hazardous solvents that permits its classification as green technique. [4]

With this aim, IRIS Technology Solutions is advancing the knowledge towards non-thermal and minimal processing ultrasound assisted processes through 3 key challenging and innovative Horizon2020 projects: SHEALTHY, AGRIMAX and PROLIFIC. Power ultrasound is utilized in the first case, for fruits and vegetables (F&V) decontamination and juices stabilization and, in the other two cases, for antioxidants and proteins extraction from several food processing residual streams. The processes are demonstrated in an industry-relevant environment through several pilot trials performed at different food micro, small and medium enterprises (SMEs) and large industries around Europe, in which Italian food industries are predominant.

SHEALTHY – Novel mild technologies to preserve freshness of fruits and vegetables

Consumer demand for fresh, sustainable and healthy food is growing in leaps and bounds, especially in one of the youngest consumer segments, in which the vegetarian and vegan diets are more popular and spread. F&V are key elements of a healthy and balanced diet providing humans with essential nutrients and bioactive compounds as vitamins and minerals. [5] The dietary shift has seen the market adapt to the newfound demand, with animal source foods substitutes (mainly F&V-based) sales and production fast- growing during these latest years.

Before these demanded F&V products can be commercialized and brought to the market, they must be processed and preserved for food ready meals by being exposed to a decontamination process in order to assure their safe consumption.
Nowadays, traditional food processing industries apply thermal conventional technologies as pasteurization and sterilization, which highly raise the treated product temperature for ensuring its microbiological safety and stability. In contrast, the use of high temperatures leads to a modification of the natural and original attributes of the product, and the destruction of some key food ingredients as vitamins and polyphenols.

SHEALTHY is a 4-years project funded under the European Union’s Horizon 2020 research innovation programme framework (GA 817936), formed by 21 partners from 8 different countries. The project focuses on developing optimal combinations of mild technologies to substitute the conventional thermal technologies used in the food processing industry during the sanitization, preservation and stabilization processes. The combinations of these novel technologies are intended to better preserve the nutritional quality of the products while prolonging the shelf-life.

Fig. 1 - US treatment along the F&V and smoothies processing chain in SHEALTHY project

In SHEALTHY project, IRIS, will develop, combine and assess the application of power ultrasound together with photodynamic technologies like High Intensity Pulsed Light (HIPL) and Blue Light to carry out, on one hand, the decontamination and sanitization of F&V products, and on the other hand, the stabilization of fruit-based smoothies and juices.

In food processing, high-intensity ultrasound at low frequencies, from 20 to 100 kHz, is useful in inactivating microorganisms. The inactivation of microorganisms is a consequence of cavitation. Cavitation is the formation, growth, and collapse of bubbles that generate localized mechanical and chemical energy. The physical effect can be the main action that is involved in microbial cell death. The ultrasound alone can provide powerful disinfection, but its use for large-scale microbiological decontamination should be further evaluated, and in combination with other technologies, it could even provide excellent results. The application of high intensity pulsed light or blue light could be considered as a complementary technology during the power ultrasound application. The photodynamic inactivation is a phenomenon that has the potential to cause microbial inactivation using visible light. It works on the principle that photosensitizers within the microbial cell can be activated using specific wavelengths to trigger a series of cytotoxic reactions. This technology is considered non-thermal, due to the decontamination of foods such as fruit juices, meat products, vegetables, and fruits is achieved by using high-intensity light pulses for a short duration of time. Recently, light emitting diodes (LEDs) of visible wavelengths have gained attention as a novel preservation technology due to their antibacterial effect.

Concerning the different typologies of ultrasound, in one hand, the application of power ultrasound in the sanitization of F&V could be carry out by using ultrasonic baths. Commercial ultrasonic baths are available in different tank capacities, ultrasonic powers or frequencies. The adjustable wave amplitude and the control of temperature made them suitable for laboratory or industrial applications. [6] In the other hand, the stabilization of smoothies and juices is carried out by the direct application of power ultrasound on liquid media and can be achieved by using ultrasonic probes. The different geometries of probes, when immersed in the liquid medium, can permit to transmit directly (cylindrical) or concentrate (conical, stepped) the ultrasonic energy.[7]

AGRIMAX– Multiple high-value products from crop and food-processing waste

In recent years, the problem of the management of agro-industrial and food processing by-products, residual matter and waste has arisen considerable interest from farmers, processors, food producers, retailers and consumers. The growing of crops and production of food goods is, in fact, associated with the generation of large waste streams, the formation of which cannot always be avoided. In particular, the food and food ingredient industry are mainly focused on the production of ingredients that consist of a single or a defined mixture of components, neglecting the material that is not considered as the main component of the manufacturing process. This is considered not only a sustainability problem related to environment security, but also an economic problem since they directly impact on the profitability of the whole process.

Actually, during food processing some profitable parts of the product cannot be consumed or are discarded because they do not reach a certain quality criterion, thus, they are considered non-compliant products which induces a lower consumer acceptance. To improve sustainability and reduce waste, it is essential to have a comprehensive understanding of the various sources of residual biomasses, being tapped and sometimes unused, generated throughout the supply chain from the farm to the table.

AGRIMAX project is designed to establish the technical and economic viability using bio-refining process on waste from crops and food processing to deliver new bio-compounds for the chemical, bio-plastic, food, fertilizers, packaging and agriculture sectors. Under the project framework, two biorefineries have been built in Italy and Spain, in which affordable and flexible processing technologies, including ultrasound assisted and solvent extraction, filtration, thermal and enzymatic treatments and spray drying modules to pretreat, separate and stabilize the agro-industrial by-products from tomato, olive, potato and cereal, have been developed. AGRIMAX has received funding from the Bio Based Industries Joint Undertaking (JU) under grant agreement No 720719. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Bio Based Industries Consortium.

Fig. 2 - US treatment for polyphenols extraction in AGRIMAX project

In the frame of AGRIMAX project, IRIS is in charge of the effective and optimized extraction of valuable antioxidants as polyphenols from potato peel, olive pomace and olive leaves by using water as solvent, and intensifying the process by the application of power ultrasound. The acoustic energy enhanced the diffusivity and solubility which eases the extraction. The properties of the extraction solvent, the particle size of the raw materials, the solvent-to-solid ration, the extraction temperature and the acoustic settings such us acoustic amplitude, acoustic energy and power, affect directly the extraction efficiency. These parameters were optimized firstly, at lab-scale (US power: 400 W) and medium-scale (US power: 1000W), and, secondly, they are currently being optimized for each extraction process, depending on the feedstock, at pilot scale in the laboratory (US power: 2000W). Finally, the efficiency achieved during the polyphenols extraction and the process feasibility study, will dictate the opportunity of installing the UAE module in the Spanish biorefinery, which represents a real industry environment.

In the last part of the project, the polyphenols extracted, which would substitute synthetic antioxidants such as BHT, BHA and TBHQ, will be incorporated as a bioactive compound for packaging and food applications: in solution, for F&V edible coating and film coating, and in compound for extrusion and film production.

PROLIFIC – Extraction and valorisation of proteins and bioactive molecules from Legumes, Fungi and Coffee agro-industrial side streams

Agro-industrial residual biomass, side streams and food production by-products such as legumes, fungi and coffee are likely to constitute rich sources of valuable ingredients. However, their potential is yet to be fully realized.

Legumes, as a source of proteins, fibres, carotenoids and phytosterols. Beans and peas industrial processing by-products generally consist of non-conforming peas, skins and plant parts, especially pods still present after the field harvest.
Fungi, as an alternative source of proteins, chitosan and b-glucans, has gained a space in the consumers diet due to a significant change in food preferences and eating habits and the search for low-fat food and health and wellness awareness.
Coffee, as source of fibres, polyphenols and caffeine. In 2017, the European Union (EU) imported almost 3 million tons of coffee from abroad. The imports were worth €8.8 billion. These imports were mainly into Germany (37 %) and Italy (19%) %), ahead of Belgium (9 %), Spain (8 %), France (7 %) and the United Kingdom (6 %) [8]. 

The coffee beverage is obtained from roasted green coffee. During this technological phase, the characteristic properties of coffee beverage (such as flavor and aroma) are developed, and the remnant thin tegument that covers and protects the outer layer of green coffee bean (coffee silverskin) is removed. Additionally, considering that more than 50% of the fruit is discarded, coffee production leads to an elevated amount of waste, such as husks or coffee silverskin (CS), of which only a slight percentage is reutilized [9].

Innovative and sustainable biorefinery processes starting from protein-rich side products could significantly contribute to face the projected global demand for food proteins (largely exceeding current production capacities) which is expected to increase by 76% in 2050 [10] due to the steadily growing world population. This predicted shortage in proteins resource is amplified by the increasing income per capita in industrialising countries in Asia and South and Middle America. [11] In particular, the increase in the demand for animal protein will result in a tremendous growth in the need for feed protein which will be hard to meet in an eco-sustainable way given the high resource footprint of producing animal-derived food products. [12]

The PROLIFIC project will apply a range of processing technologies to agro-industrial residues of legumes, fungi and coffee in order to recover significant amounts of proteins/peptides, fibers and other value-added compounds. Once extracted by economically and environmentally sustainable protocols, the outputs will undergo enzymatic modification and conditioning techniques in an upscaled, industrially-relevant environment. Ultimately, this will provide viable amounts of the compounds and fractions necessary to produce 16 prototypes for the food, feed, packaging and cosmetic sectors. PROLIFIC has received funding from the Bio Based Industries Joint Undertaking (JU) under grant agreement No 790157. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Bio Based Industries Consortium.

In PROLIFIC, IRIS, applies power ultrasound to improve the protein extraction efficiency in the case of recalcitrant substrates such as coffee and fungi residues. Lab scale trials are being performed varying sonication time, output power and pulse mode in order to increase performances of protein extraction. The protein extraction from biological sources can be achieved by the alkaline/acid precipitation technique. After the removal of fiber and fat and the milling of the sample to determine particle size, the alkaline extraction is applied to solubilize protein, followed by filtration to remove insoluble carbohydrate material. The selected reaction conditions will be used for upscaling the intensification process using a dynamic sonication system. Microwave-assisted extraction will also be evaluated for improving the protein extractability of the selected raw materials applying a response surface methodology (RSM). Parameters such as extraction time, type of solvent (acid/alkali/water) and solid to liquid ratio will be optimized.

Fig. 3 - Protein extraction from legumes, fungy and coffe by-products in PROLIFIC project

The protein extracts from biomass streams will be subjected to different treatments such as purification, concentration, and stabilization, and converted into ingredients for protein or antioxidant enriched food (e.g. cereals, dough) and feed formulations and components for polymer and composite formulations for, for example, cosmetic packaging.

Italian Food Industry: Novel and Circular opportunities

The food and beverage processing sectors are one of the most important Italian industries. Italian food sector production, processing and retail remain heavily fragmented, with a very competitive business environment. Even the biggest Italian food retail businesses are small compared to other major international players. The relatively high costs to procure novel food and sustainable processing technologies are usually not affordable for micro and SMEs as high innovation and investment capacity are needed. Under the framework of these three projects, it is intended to increase some Italian food processing companies’ competitiveness and facilitate them to assess and integrate residual streams valorization processes, which will lead to a positive growth in their regional and national market size, due to the commercialization of new products, their shelf-life prolongation and nutritional quality preservation, a more efficient process caused by costs and time decrease, and finally, the economic and environmental benefit of exploiting the residual streams valorization.

Some Italian food processing SMEs and some well-known large industries constitute the different business cases of these three collaborative projects in which, the techniques above-mentioned among other, will be upscaled, integrated and tested in their own products, processes and facilities.

Fig. 4 - Italian companies: Business Cases

[1] Rojas, M. L., Miano, A. C., & Augusto, P. E. D. (2017). Ultrasound Processing of Fruit and Vegetable Juices. Ultrasound: Advances in Food Processing and Preservation. Elsevier Inc. https://doi.org/10.1016/B978-0-12-804581-7.00007-5

[2] Cárcel, J. A., García-Pérez, J. V., Benedito, J., Mulet, A. (2012). Food process innovation through new technologies: Use of ultrasound. Journal of Food Engineering, 110(2), 200-207. doi: 10.1016/j.jfoodeng.2011.05.038

[3] Fernandes, F. A. N., Rodrigues, S. (2008). Application of Ultrasound and Ultrasound-Assisted Osmotic Dehydration in Drying of Fruits. Drying Technology, 26(12), 1509-1516. doi: 10.1080/07373930802412256

[4] Chemat, F., Zill, E. H., Khan, M. K. (2011). Applications of ultrasound in food technology: Processing, preservation and extraction. Ultrasonics Sonochemistry, 18(4), 813-835. doi: 10.1016/j.ultsonch.2010.11.023

[5] World Health Organization. (2018). Healthy Diet. Fact Sheet N394, (August), 6. https://doi.org/10.1080/00380768.2011.576397

[6] Rodriguez, Ó., Eim V., Rosselló, C., Femenia, A., Cárcel, J., Simal S. Application of Power Ultrasound on the Convective Drying of Fruits and Vegetables: Effects on quality. Journal of The Science of Food and Agriculture, 2017. doi: 10.1002/jsfa.8673
[7] Mason, T. J., Riera, E., Vercet, A., Lopez-Buesa, P. (2005). 13 - Application of Ultrasound. In D.-W. Sun (Ed.), Emerging Technologies for Food Processing (pp. 323-351). London: Academic Press.

[8] https://ec.europa.eu/eurostat/en/web/products-eurostat-news/-/EDN-20181001-1

[9] Toschi, T. G., Cardenia, V., Bonaga, G., Mandrioli, M., & Rodriguez-Estrada, M. T. (2014). Coffee silverskin: Characterization, possible uses, and safety aspects. Journal of Agricultural and Food Chemistry, 62(44), 10836–10844. https://doi.org/10.1021/jf503200z]

[10] European Commission. (2016). European Research and Innovation for Food and Nutrition Security. Food 2030 High-level Conference Background Document. https://doi.org/10.2777/20654

[11] Gustavsson, J., Cederberg, C., Sonesson, U., van Otterdijk, R., & Meybeck, A. (2011). Global Food Losses and Food Waste: Extent, Causes and Prevention, Rome: Food and Agriculture Organisation of the United Nations. Philosophical Transactions of the Royal Society B: Biological Sciences (Vol. 365). https://doi.org/10.1098/rstb.2010.0126

[12] Chatzopoulos, T., De Rademaeker, E., Fellmann, T., Genovese, G., Jensen, H., Kanadani Campos, S., … Weiss, F. (2016). Prospect for the EU agricultural markets and income 2016-2026. Agriculture and Rural Development, (December). Retrieved from https://ec.europa.eu/agriculture/sites/agriculture/files/markets-and-prices/medium-term-outlook/2016/2016-fullrep_en.pdf

Edurne Suarez

Edurne Suarez

Project and Innovation Manager at IRIS Technology Solutions. Msc in Industrial Engineering with specialization in Materials at Polytechnic University of Catalunya (UPC-ETSEIB), Spain. Visiting research assistant at Zero Waste Byg group at Technical University of Denmark (DTU) working on the valorization of ocean waste as construction materials. Edurne comes from a background in technological innovation, managing and executing research and innovation tasks in several European collaborative R&D&i projects.

Óscar Rodríguez

Óscar Rodríguez

Senior Research Scientist at IRIS Technology Solutions. Agroindustrial Engineer (University of Tolima). M.Sc., Chemical Science and Technology (University of the Balearic Islands). Ph.D. Chemical Science and Technology (University of the Balearic Islands). With more than 10 years of experience in the intensification of mass transfer processes by means of power ultrasound application. Also, Dr. Rodríguez has been working on projects related to the revalorization of agro-industrial by-products among other research projects.

Simona Neri

Simona Neri

Project and Innovation Manager at IRIS Technology Solutions. PhD in supramolecular chemistry at the University of Padua, working on the use of self-assembled gold nanoparticles as sensors and as molecular switches in biocatalysis. Previously, she obtained her Master degree in Organic Chemistry carrying out her final project on bioactive peptides at the University of Barcelona. She also has expertise in packaging technology thanks to her bachelor degree in “Packaging Science and Technology” and her job experiences in Procter&Gamble, GlaxoSmithKline and Lindt&Sprüngli.