By: Anu Bhusani *
Flavour is the first thing you relish in your morning coffee. So what does flavour constitute – aroma or taste of the food? The answer is both. Flavour is a sensory impression of food that is felt simultaneously by the tongue as taste and the nose as the aroma. Humans can perceive only five tastes (sweet, sour, bitter, salty and umami), but can distinguish one trillion different aromas. Also, aroma contributes to 80 percent of what we perceive as a taste of food. Hence, the flavour is an important parameter that maximizes the quality, acceptability and global competitiveness of a food product. However, flavours in foods are greatly degraded by chemical or physical reactions during harsh food processing conditions. Here, nanotechnology can aid in flavour retention, flavour enhancement, controlled release of flavour and masking of off-flavours. Let us understand in brief how nanotechnology has a role in the flavour of foods.
Nanoencapsulation of Flavours
Nanoencapsulation is the process of packing a core compound within a wall matrix at dimensions in nanoscale (< 1000 nm). Flavours can be encapsulated using various techniques to obtain the encapsulated product in powder, paste or liquid form. Mostly, flavours are encapsulated using spray drying; spray chilling; homogenization and extrusion techniques. The choice of wall material (e.g. biopolymers, protein, carbohydrates, and lipids) depends on the end use of the encapsulated flavour. For use in bakery products, powder form of flavour encapsulated using starch or protein is preferred; in beverages, liquid form of flavour emulsified with lipids is used. Flavours are encapsulated prior to the crucial processing step in order to protect the compound from degradation. However, for use in frozen products like ice creams, flavours are directly added to the product during homogenization or agitation processes which act as an encapsulation technique. The emulsion particles produced during homogenization protect the flavour compounds during processing and storage.
Nanoencapsulation in Controlled Flavour Release
Nanoencapsulation is advantageous not only to protect the flavour during processing and storage but also to aid in controlled release of flavours from the food matrix. The major release mechanisms are diffusion, swelling and fracturation. Controlled release of flavour is achieved by the wise use of wall materials in conjunction with the end product. For instance, in the case of candies or chewing gums, the flavour has to be released in the mouth while chewing. To this end, cold water-insoluble materials such as: gelatine; waxes; or fats can be used for encapsulation of flavours to aid in flavour release by physical rupture (chewing) in the mouth. This way, fracturation is the controlled release mechanism which promotes instant flavour perception for a prolonged period of time. On the other hand, in the case of tea flavours that remain inside the bag, the aroma has to be felt on dissolution with hot water and the taste has to be perceived by the mouth, hence carbohydrate/protein based wall materials are used.
Nanoencapsulation in Masking Off-flavours
Another interesting application of encapsulation is the masking of off-flavours produced by compounds added into foods or that are developed during storage. Nanoencapsulation is used to mask the flavour of omega-3 oils (fish oil) added as functional ingredients to foods. Similarly, nanoemulsified flavour oils containing protein-based coating are shown to delay the degradation of oils and prevent the release of rancid odours in beverages.
Microencapsulated flavourings are widely used by leading food manufacturers and the use of nanoencapsulated flavourings is still in its nascent stage. However, the advantages of nanoencapsulates over microencapsulates is gradually motivating food manufacturers to utilize them for the development of foods with exceptional flavour characteristics.
Nanoparticles as Flavour Carriers Nanoparticles of silicon dioxide (SiO2), also known as silica are widely used as a flavour carrier in food products. Silicon dioxide is comprised of aggregated nano-sized primary particles, which can further agglomerate to form larger structures (i.e. >100 nm). It has been registered by the European Union as a food additive (E551) and can be added at a level of <10,000 mg/kg in foods excluding infant products.
Salt and Sugar in Nanoform
Salt, sugar and artificial sweeteners are technically regarded as flavour improvers. The use of nanotechnology in modifying the physical properties of salt and sugar has a profound role in its beneficial health effects. Reducing the particle size of salt to nanoscale increases its surface area, leading to increased dissolution rate in saliva and hence a saltier perception at a low salt level. This nano-sized salt can have potential applications in surface-salted foods. Similarly, nano sugar has been developed by pharmaceutical companies which claim high sweetness at lower sugar concentration. They use nanotechnology for sugar extraction where the process dislodges negative carbon from sugar cane component, which is the contributing factor of chronic diseases. The nano sugar is also clinically proven to have a lower rise in blood glucose level compared to conventional sugar in both normal and diabetic individuals.
Major efforts need to be undertaken by governments, food safety authorities and manufactures to ensure and advocate the safety of foods containing engineered nanomaterials (nanoencapsulates, nanoparticles). With that in place, nano flavours will carve a niche for itself in the food and flavour industry.
* Ph.D. Biological Sciences, CSIR-Central Food Technological Research Institute, Mysore, India