Nanotechnologies in Food Microbiology Overview, Recent Developments, and Challenges
Foodborne illness is a major issue caused by the pathogens that results in moderate to severe illness and death via bacterial infections and intoxications in contaminated foods (Scallan et al., 2011). Moreover, spoilage microorganisms will bring a negative influence on food quality and shelf life that leads to food deterioration. Therefore, there is an increasing awareness of the protection of the food system against pathogenic and spoilage microorganisms to promote food quality, safety, and security. At present, many physical food preservation techniques are commonly being practised. These include thermal processing, food irradiation, pulsed electric field processing, high-pressure processing, plasma processing, and others (Fu et al., 2016). However, physical food preservation techniques may affect the qualitative aspects of the food system, like texture, flavour, and nutritional value. Recently, natural antimicrobial agents have gained public attention due to greater awareness of food quality and safety among consumers. Antimicrobials are food additives that inactivate or suppress the growth of pathogenic microorganisms in food systems (Tiwari et al., 2009). The addition of antimicrobial agents in the food system can overcome the negative impacts of physical processing techniques.
Therefore, there is an increasing interest in the search for new approaches to food preservation. For instance, essential oils can be used as safe preservatives to inhibit bacterial activity (Donsi et al., 2011). The addition of antimicrobial agents suppresses microbial growth through environmental control. However, antimicrobial agents are chemically reactive species, which can create potential problems when applied to the food system. For example, antimicrobial agents would cause negative impacts in the physical stability or degrade the bioactive compounds of the food system. Thus, considerations on the concentrations of antimicrobial agents to be applied in the food system are important to ensure the qualitative aspects of the food product are not affected (Donsi et al., 2011; Weiss et al., 2009).
Encapsulation is a process whereby the active agent is entrapped by wall material, yielding particles in nanometres (nano-encapsulation), micrometres (microencapsulation), or millimetres. Microencapsulated particles have sizes ranging from 1 to 1000 pm, while nano-encapsulated particles have sizes ranging from 1 to 100 nm. Currently, nanotechnology is actively applied in the food industry, with the promising benefits in processing, packaging, storage, transport, functionality, and food safety. Industry and academic researchers are giving attention to nanotechnology in countering matters corresponding to food and nutrition in the process of encapsulating, protecting, and releasing functional active agents (Ezhilarasi et al., 2013). There are many nano-encapsulation technologies with the challenges of selecting a suitable method with optimal parameters to obtain the nanostructures with recognizing the type of nanomaterial perfect for a desired bioactive compound.
Nanoencapsulation is receiving attention recently to encapsulate various antimicrobial agents such as phytochemicals, alkaloids, and essential oils. This technique helps to reduce the microbial contamination in the food system with enhanced food sensory characteristics (colour, flavour, taste, and texture). Nanotechnology may offer innovative and economic growth for food safety and security shortly. The selection of wall material is an important factor in the nanoencapsulation technique. The wall material of nanocapsule acts as a protective film to isolate the core materials against the exposure of an extreme environment. Both the physico-chemical properties of the active agent and the intended applications have to be considered in the selection of wall materials. There are a various natural and synthetic wall materials available such as polyethylene, carbohydrates (starch, pectin, cellulose, and chitosan), proteins (casein, whey protein, albumin, and gelatin), lipids (fatty acids, wax, phospholipids, and paraffin), and gums (alginate, carrageenan, and gum arabic) (Da Silva et al„ 2014; Ribeiro-Santos et al„ 2017). Nevertheless, the use of natural polymers is preferred as their non-toxicity and lower costs than synthetic polymers (Prajapati et al., 2013).