Food processing and preservation methods such as heating, drying, salting, freezing, chilling, curing, sugar addition, and acidification have been applied against spoilage and pathogenic microorganisms in foods (Leistner, 2000b). On the other hand, these classical technologies have negative impacts to nutritional value (e.g. loss of vitamins and essential nutrients during heat treatments) (Lado and Yousef, 2002)and changes in sensory attributes in the food products (Raso and Barbosa-Canovas, 2003). Even though the microbial safety and stability are important in producing foods, current consumer demand for more natural, fresh-like, safe, and stable foods need to be considered (Rastogi, Raghavarao, Balasubramaniam, Niranjan& Knorr, 2007). This situation urges food manufacturers, product developments, and quality assurances to develop novel techniques with “minimal”processing technologyand combine these mild techniques which provide alternative to traditional technology and produce safety and nutritious food products (Alakomi, Skytta, Helander&Ahvenainen, 2002).
Leistner (1995a) has been developed a food preservation technology with combining several factors and known as hurdle technology. Hurdle technology is a concept to food safety and preservation that are designed to maintain microbial stability and improve total quality of foods withoutdiminish nutritional value and sensory of the products (Leistner and Gorris, 1995).
This technology exploits synergistic between traditional and novel technology to establish a series of preservative factors (hurdles) and keepstandard population of microorganisms in foods under control. Themost common and important hurdles used in food preservation to inhibit the numbers of microorganisms and to ensure product safety and stability are temperature, water activity (aw), acidity (pH), competitive microorganisms (e.g., lactic acid bacteria), redox potential (Eh), and preservatives (e.g., sorbate, nitrite) (Leistner, 2000a).
The advantageous of combining technologies are enhance the lethal effect of nonthermal processing (Pagan, Esplugas, Gongora-Niero, Barbosa-Canovas& Swanson, 1999; Yousef, 2001), prevent proliferation of microorganisms (Raso and Barbosa-Canovas, 2003), andminimize the intensities of the treatments(Ross, Griffiths, Mittal &Deeth, 2003).However, an antagonistic effect may occurin some conditions (Figure. 1) which means that the combination of hurdles failed to provide a good antibacterial effect in foods and the effectiveness of that combinations is less than any single targeting hurdles used alone (Raso and Barbosa-Canovas, 2003). Therefore, further studies about understanding the impact and synergetic between different preservation factors in foods are needed. In this article, some successful combinations of nonthermal technology with other food preservation techniques will be reviewed.
Figure 1.Possible effects obtained by combining different preservation technologies...