Flavour generally results from the breakdown of precursor compounds into components of both volatile and non-volatile forms with diversity in their physiochemical nature. While the volatile part of the compounds is responsible for the aroma and taste, the non-volatile exponents are mainly associated with the taste. A number of compounds actually render the aroma that we find in the food products- lactones, aldehydes, ketones, esters, short chain fatty acids, phenolic compounds, diacetyls and many more. The plants have been the original resources for quite a number of these flavouring agents and in recent times a knowledge about the original compounds have led to the development of synthetic compounds.
Involvement of The Microorganism:
The flavouring industry is still booming and there is a growing need among the consumers for flavour and aroma of natural origin. The microbes can synthesize many of the flavour producing compounds as secondary metabolites or as an intermediate during their metabolic processes. Generally they breakdown the amino acids or the saccharides into flavour and aroma causing compounds. In general, we don’t prefer our products of consumption as tasteless, non-aromatic substances.
The probiotic products are also not away from this general feeling of the consumers. Wouldn’t it be nice if the probiotic product is so designed that some of the bacterial components in it can themselves provide with the due aroma and flavour to make them all the more acceptable? There is indeed a good possibility for the application of the selected probiotic strains in the production of flavour and aroma. There are many compounds that can be synthesized by the beneficial bacteria to this effect.
The common ingredient of artificial butter, diacetyls has found increased application whenever there is the need to imitate the buttery flavour such as in beverages and fermented food products like cheese, yoghurt, etc. The compound has been reportedly produced by quite a number of the probiotic strains of lactic acid producing as well as other microorganisms. Some of the bacteria used extensively for its production include Lactobacillus, Lactococcus lactis, Leuconostoc mesenteroides, S. thermophilus, etc.
Researchers have tried to investigate the factors behind the ability of such bacteria in the production of diacetyl and other related compounds that find their application in the food processing industry. It has been found that in dough cultures the bacteria producing lactic acid are capable of producing diacetyls with the concerted effects of the enzymes like acetoin dehydrogenase, acetolactate synthase, diacetyl reductase and lactate dehydrogenase on different substrates. Some scientists have reported for the negative impact of citrate on diacetyl synthesis by the probiotic bacteria L. rhamnosus. Proper channelized research in the effective utilization of the diacetyl producing probiotic strains can have bigger implication to be used in the probiotic industry.
One of the most common types of flavouring compounds, the ester based compounds find their increased application due to the nice fruity smell that is associated with them. They have been found to be used in the jams, jellies, candies and some of the beverages, fermented products, wines and so on. In particular the acetate esters like the isoamyl acetate, ethyl acetate have become more popular and are used increasingly in the food industry to mimic the fruits for their aroma. In fermented dairy products like cheese, methyl or ethyl esters render the associated fruity smell to them. The strains from the probiotic bacteria Lactococcus lactis have been investigated for the presence of some of the unique esterases in them which can bring about the esterification reaction responsible for the fruity aroma and flavour.
The flavour range of the lactones vary from buttery, nutty, fruity, coconut and creamy. They are basically esters (cyclic) of hydroxy acids and with the wide range of flavours in their kitty they can contribute to the flavour of different kinds of food products. The concept of lactone production by the microorganisms came to the light when it was found that a significant number of microbes are able to metabolize hydroxy acids. Several reports suggest that the media of fermented food products contain many of the lactone derivatives needed for flavouring.
The presence of the creamy, or the other lactone associated flavours in the dairy products are quite desirable. In particular, the compound 6 pentyl 2 pyrone is on high demand for the coconut flavour that they produce in the food products. In recent times, reports for some of the strains of Streptococcus and Lactobacillus strains for their lactone synthesizing abilities have been presented. With those reports the hope for the production of lactone based versatile aroma and flavour by the probiotic bacterial strains is now a possibility.
Pyrazines provide a roasted and nutty flavour to the food products and are essentially nitrogen based heterocyclic compounds. Initially, they were detected in cooked food however with the change in cooking processes in due course of time there is lack of pyrazine type flavours from our foods. Some of the microorganisms have been found to be involved in the synthesis of pyrazine like compounds. However, very little is known about the ability of the probiotic bacteria to produce such compounds.
Vanillin based flavour producing compounds have found wide acceptance across food products. They were initially isolated from the beans of vanilla planifolia. However, there is a marked scarcity in the availability of those beans nowadays and that has shifted the focus of the flavour and aroma researchers towards microbial based production of the compounds. A good number of bacteria that also include the ones from the Bifidobacterium and Lactobacillus species are now being investigated for their potential role in the production of vanillin type compounds.
In addition to the aforesaid compounds, many others like alcohols and its derivatives (mainly 2-pphenyl ethanol that gives a rosy smell), aldehydes like benzaldehyde for their natural fruity smell have found good acceptability in the food industry.
The flavour and aroma is an essential ingredient of any food supplements nowadays. As such the probiotic products cannot be away from it. However, the addition of artificial flavours can cause apprehension about the viability and effectivity of the probiotics. Therefore, the addition of flavours and aroma which are the result of the probiotic bacteria themselves can have better acceptance among the consumers.