Food process innovation combining early and recent technologies

Smart and judicious business managers know that innovation is the best tool to overcome difficult situations and envision new opportunities. Food processors have an established history of leadership in research and innovation of both products and processes. In any field, though, wise decisions require as much information as is available. The knowledge developed at research centres can assist industrial needs in this field within the contemporary open innovation trend. In this context, a summary of the knowledge on the combination of antimicrobial agents with advanced food preservation technologies is presented.

The tendency of consumers towards eco – nomical and convenient food products without renouncing the typical sensory and nutritional properties is well known. Leaving aside the elaboration of new food products, food manufacturers have other ways to meet consumer’s demands. It is possible to improve traditional methods or develop new processes grounded on technologies taking profit of different physical and chemical characteristics of food. Another option would be a combination of the previous approaches.

Several non-thermal technologies have been evolving since the last few decades of the precedent century. Among them, pulsed electric field (PEF) processing is a technology adopted from genetics where it is known as electroporation. It leads to the formation of pores on cellular membranes due to the stress caused by the external electric field perturbation.

Currently, there is a great amount of scientific knowledge about the variables influencing such process when it is applied to food products. Microbial susceptibility of pathogens and enzymatic resistance of spoilage agents are among the most important factors because one of the purposes of food processing is achieving the highest level of food stability from any point of view: microbiological, physical and chemical. Other important aspects are the electric properties of the food, and several processing parameters being strength of electric field and processing time the most remarkable1. Despite the thousands of volts required in the treatment, it is a very efficient technology because electric energy does not have to be transformed to another kind of energy, and typical processing time is in the order of a few milliseconds. The technology is considered a non-thermal process when it is properly implemented as the increase of product temperature due to ionic movement of food components in a forced electric field can be controlled with a refrigerating system as well as the selection of the shape, polarity, width and frequency of the pulses.

Moreover, economical, engineering and energetic aspects of the application of PEF technology to the food industry have been examined2. Considering all the information as a whole, it is reasonable to conclude that PEF technology is a feasible alternative to thermal processing. Currently, the main inconvenience hindering the scale up of the PEF technology to the industry is the lack of higher throughput devices that would permit a verification of lab results.

Recovering the idea of achieving consumer claims through an improvement of traditional tools, antimicrobial agents have been used since ancient times with a long-established effectiveness. It is well-known that some of the antimicrobials (e.g. nisin, lysozyme) act on microbial membrane envelopes whereas others (e.g. organic acids) exert their toxic effect, which consists of disturbing metabolic pathways, only after entering into the cells. Their use has been updated with the contemporary hurdle concept. It states that a combination of barriers enhances the desired effects of food preservation like maintaining or improving food shelf life while dwindling the unwanted aspects such as sensory modification and nutritional degradation, thanks to a reduction of the intensity of each obstacle.

The group New Technologies for Food Processing at the University of Lleida (UdL) has been doing active research in these fields for around 20 years. Lately, the main effort is directed towards the analysis of the effect of PEF processing on sensory, nutritional properties and shelf-life of several flowing foodstuffs such as juices and dairy products. Some of such studies were aimed at performing a direct comparison between PEF and thermal treatments. In the area of antimicrobials, it has been investigating the effect of natural products applied as edible coatings or encapsulated agents to ready-to-eat and non-thermal minimally processed products.

Table 1 gathers some of the recent microbial results reported on the combination of PEF and antimicrobial technologies. Data obtained to date show that the outcome is either outstanding when the use of both technologies lead to the expected effect, or hardly observed. Going further into the details, the analysis of the results immediately after processing proves that the nature of the target microorganism, specifically its envelopment structure, is a key factor3. However, studies reporting the long term effect of the treatment combination applied to several fruit juices and other fluid foods point to an increase of shelf life. In specific cases, it appears dependent on the sequence of treatment application4. Finally, research to understand the consequences of the combined approach on sensory properties of processed goods is in an initial stage5. Current data suggest that protein-related agents produce fewer sensory changes than organic acids and vegetal extracts when they are dosed with enough levels to exert antimicrobial effects on foods.

Table 1 Summary of studies dealing with combination of PEF and antimicrobial substances (adapted from (6))

Looking closely at the information about the use of several preserving technologies, some interesting pros and cons can be outlined. Firstly, it seems dependent on the specificity of the combined treatment. Therefore, an exhaustive investigation should be carried out in each specific proposed combination to ensure that real data confirms the expected behaviour. Food product matrix, target microorganisms and processing conditions are so interrelated that the effects of each variable can be confounded, making process optimisation quite difficult. This fact, though, should not be taken as a nuisance since, as commented previously, the treatment often reveals a synergy between applied technologies leading to a less severely processed product. Such a reduction in the level of processing is commonly understood by consumers as a quality improvement.

Secondly, some processing conditions may change, even drastically, the typical sensory properties of natural products. Again, this fact can be interpreted from opposite standpoints. It could be an issue for currently marketed goods even though it is an open door to develop innovative food commodities.

A final issue to keep in mind when discussing combining technologies is to realise that acting on different targets of the same unwanted agent reduces the likelihood of developing treatment resistance. On the other hand, in other words, it enables the increase of the safety margin of both producers and consumers in a time when the latter are easily attracted to the obvious advantages of minimally processed foods without realising the potential risks of these new ways of processing.

Combining food preserving technologies is a challenging strategy in the food industry. Such claims may seem strange as it is not a revolutionary way of thinking. Actually, this approach has been used for food innovation for many centuries. The innovation consists of an intelligent combination of a set of different and natural antimicrobials with non-thermal technologies to meet the consumers’ demands of fresh-like, safe, attractive and healthy foods. The food industry could benefit from this strategy if current research efforts allowed the unravelling of the underlying mechanisms of the interactions among food matrices, microbial agents, and processing conditions.

References

1. Food preservation by pulsed electric fields: an engineering perspective. Morales de la Peña, M., Elez- Martínez, P. and Martín-Belloso, O. 2, 2011, Food Engineering Reviews, Vol. 3, pp. 94-107

2. Lelieveld, H.L.M., Notermans, S. and de Haan, S.W.H., [ed.]. Food preservation by pulsed electric fields. Boca Raton : Woodhead Publishing Limited, 2007

3. Soliva-Fortuny, R., et al. Nonthermal processes as hurdles with selected examples. [ed.] H.Q. Zhang, et al. Nonthermal processing technologies for food. Ames : Wiley-Blackwell, 2011, pp. 406 – 427

4. Microbiological shelf life and sensory evaluration of fruit juice treated by high-intensity pulsed electric fields and antimicrobials. Mosqueda-Melgar, J., Raybaudi-Massilia, R.M. and Martín-Belloso, O. 2011, Food and Bioproducts Processing, p. doi:10.1016/k.fbp.2011.03.004

5. Combination of high-intensity pulsed electric fields with natural antimicrobials to inactivate pathogenic microorganisms and extend the shelf-life of melon and watermelon juices. Mosqueda-Melgar, J., Raybaudi- Massilia, R.M. and Martín-Belloso, O. 3, 2008, Food Microbiology, Vol. 25, pp. 479 – 491

6. Combination of pulsed electric fields with other preservation techniques. Sobrino-López, A. and Martín- Belloso, O. 2011, Food Bioprocess Technology, pp. doi:10.1004/s11947-011-0512-z

7. Enhancing inactivation of Staphylococcus aureus in skim milk by combining high-intensity pulsed electric fuelds and nisin. Sobrino-López, A. and Martín- Belloso, O. 2006, Journal of Food Protection, Vol. 69, pp. 345 – 353

8. Increased inactivation of exopolysaccharide-producing Peidococcus pparvulus in apple juice by combined treatment with enterocin AS-48 and high-intensity pulsed electric field. Martínez-Viedma, P., et al. 1, 2010, Journal of Food Protection, Vol. 73, pp. 39 – 43

9. Effect of enterocin AS-48 in combination with highintensity pulsed-electric field treatment against the spoilage bacterium Lactobacillus diolivorans in apple juice. Martínez-Viedma, P., et al. 5, 2009, Food Microbiology, Vol. 26, pp. 191 – 496

10. Enhanced bactericidal effect of enterocin AS-48 in combination with high-intensity pulsed-electric field treament against Salmonella enteric in apple juice. Martínez-Viedma, P., et al. 2, 2008, International Journal of Food Microbiology, Vol. 128, pp. 244 – 249

11. Enhancing the lethal effect of high-intensity pulsed electric field in milk by antimicrobial compounds as combined hurdles. Sobrino-López, A. and Martín- Belloso, O. 5, 2008, Journal of Dairy Sience, Vol. 91, pp. 1759 – 1768

12. Inactivation of Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes by combining high-intensity pulsed electric fields and malic acid in apple juice. Raybaudi-Massilia, R.M., Mosqueda-Melgar, J. and Martín-Belloso, O. Cork, Ireland : s.n., 2006. Workshop on Application of Novel Technologies in Food and Biotechnology

13. Non-thermal pasteurization of fruit juices by combining high-intensity pulsed electric fields with natural antimicrobials. Mosqueda-Melgar, J., Raybaudi-Massilia, R.M. and Martín-Belloso, O. 3, 2008, Innovative Food Science & Emerging Technologies, Vol. 9, pp. 328 – 340

About the Authors

Robert Marsellés-Fontanet is a chemist who moved his orientation to the food area after a decade of experience working as a quality, production and research manager in several food industries. He achieved his PhD in Food Technology at the University of Lleida where, currently, he is a member of the New Technologies for Food Processing research group. His interests are focused towards improving the efficiency of actual food processing technologies, developing non-thermal food processing and adding value to wastes generated by agriculture and food industries.

Olga Martín-Belloso is presently Professor of Food Science and Technology and Head of the research unit New Technologies for Food Processing, University of Lleida, Spain. Her research interests are focused on the development of ready-to-eat, safe and healthy products by combining the already existing processing technologies with novel techniques, as well as the valorisation of wastes generated by the fruits and vegetables processing industries. email: [email protected]