Modifying the composition and original forms of naturally occurring plants is an art that humankind has been constantly developing and fine-tuning for thousands of years. Professor Dr Joachim J. Schmitt describes current research work at Fulda University of Applied Sciences to select food constituents according to how they alter taste sensations so as to promote health.
It is no wonder that the discovery of how to make fire and change natural foodstuffs by heating them triggered a major evolutionary step in humanity’s development. Only then did it become possible to break down the starch contained in grasses and tubers so that the human body could digest them and use them as sources of energy. Starch that is not heated exists in nature in an extremely compressed form (in so-called starch granules) that cannot be digested by the human organism.
Modifying naturally occurring plant constituents is therefore one of the basic principles for preparing natural substances for human digestion. This principle is still used today to convert plants into raw materials for food by chopping, extracting, heating and fermenting them. The substances in these raw materials are then converted into human foodstuffs by recombining them and subjecting them to physical and chemical treatment (such as heating and adjustment of the pH value). This development of new combinations (recipes) for producing food that began thousands of years ago has now been developed to a very high scale and will probably carry on for as long as humans continue to live.
Variety and recombination of raw material constituents
The wealth of possible combinations of raw materials that is currently available for producing human foods is mainly due to the progressive breakdown of plants into their basic constituents. Technology and development now make it possible not only to isolate starch, proteins and fats from cereal grains, but also to separate the layers that envelop the cereal grain and produce flours that are rich in protein and glucan (e.g. aleurone flour). Milk can now also be separated not just into fat and protein, but into fractions of various fatsall of which have very different technical effects, and into many different proteins that show very special behaviour both in terms of nutrition physiology and with regard to food manufacturing methods.
This unparalleled variety of raw material constituents nowadays leaves the field wide open for recombining (formulating) substances for food production. This is reflected in the immense variety of foods with different formulations in our supermarkets and also in the fact that every day sees the introduction of new food products with modified tastes, colours and textures.
Apart from the motivation to amaze consumers’ tastebuds with ever new compositions of food ingredients, there is, however, also a need to reduce food prices in order to make foods affordable to as many consumers as possible and to acquire a competitive edge over other manufacturers of comparable products. This is why we can now buy meat salads, for example, in which meat is not the main ingredient in terms of quantity. Indeed, food preparations that mainly consist of inexpensive fillers and bulking agents and readily available plant proteins are currently conquering the market. Here, it is the price and availability of inexpensive raw materials that determine the formulation of foodstuffs. Taste, colour and texture are adjusted using herbs and spices, colourful plant ingredients and fats that carry flavour.
Search for healthy substitutes
Relatively large quantities of sugar, salt, flavour enhancers and fats are often added to such foods to achieve a satisfying taste. When such food compositions are eaten frequently, this addition of active taste-enhancing substances that is mainly necessary in industrial food production means that the human body takes in too much of these substances, which otherwise have a positive connotation in terms of taste and are therefore popular.
This excessive intake is currently suspected of playing a crucial role in causing diseases that affect large swathes of the population. These include metabolic disorders such as diabetes and obesity, as well as arteriosclerosis that can ultimately lead to heart attacks and stroke.
To prevent such widespread diseases, some countries and international institutions such as the European Union are calling for a reduction in the daily intake of sugar, salt and fat. However, reducing these key taste ingredients poses enormous problems for the food industry, because it will not be able to meet consumers’ expectations in terms of taste if it uses less salt, sugar and fat. The food industry is therefore searching intensively for substitutes for sweet, salty and fat-based tastes. In this context, the strategic alliance known as the Natural Life Excellence Network 2020 (NatLifE 2020), initiated by the German Federal Ministry of Education and Research (BMBF) and coordinated by BRAIN, is raising high hopes. The Food Technology Department of Fulda University of Applied Sciences is a partner of this alliance.
On the other hand, the huge range of ordinary food ingredients that is currently available also offers potential for reducing sugar and salt in our diet. This is based on the hypothesis that some frequently and generally used food ingredients have the inherent ability to bind salt and sugar and therefore “hide” them from our sense of taste. They can also influence the taste sensors on the human tongue so that they perceive less sugar or salt. If we were to exchange such food ingredients for others that do not have this ability, we could use less sugar or salt to obtain the same sweet or salty taste.
However, scientific insights into the taste-modulating properties of frequently used basic substances such as proteins and hydrocolloids are still rudimentary. We will go on to present some findings of our own research efforts in this field.
Inhibiting the perception of sweetness through protein-enriched plant extracts
In a tasting experiment with 16 people, participants were asked to compare the sweetness of two food samples. They were supposed to judge which sample tasted less sweet. The paired samples (AFC test) in which both contained the same composition of food ingredients, but one sample held a higher concentration of a protein-rich extract from the plant being examined. The findings of this test are summarised in Fig. 1.
This chart shows that increased concentrations (2g/100g of food) of protein-enriched chia, cranberry and whey fractions significantly reduce the impression of sweetness, whereas that is not the case with almond and sunflower fractions, in particular. The significance threshold is represented by the grey line in 12 corresponding responses.
Whey protein, for example, is suspected of reducing the sweetness of foods. It is currently one of the most frequently used food ingredients, where the aim is to enrich the protein content of food inexpensively, or to improve the processing of raw materials in food products.
Inhibiting the perception of salt by means of fillers and bulking agents
Fillers and bulking agents (so-called hydrocolloids) are further constituents of modern foods that are very widespread. They are used, for example, to make a soup creamy, to stabilise sausages or thicken sauces. Even small quantities of 0.5% of such substances significantly alter the taste sensation of foods, as shown in the following figure. In this test, people were asked to judge whether a food sample possibly tasted less salty than a reference sample offered to them. Fig. 2 shows the result.
The evaluation of this test shows that the bulking agents gellan gum, guar gum, sodium alginate, xanthan and especially konjac gum significantly reduce the salty taste of a food sample. So if we were to replace the frequently used thickening agent sodium alginate with native starch or gelatine in food products, consumers might be satisfied with less salt in the food.
Researching the effect of food ingredients
The thickening effect of the bulking agents examined here is very different, though, at the same concentration. The degree of thickening (technical term: increase in viscosity) is, however, a key factor in reducing sweet, salty, sour and bitter tastes. The more viscous a solution is, the more difficult it is for the taste substances to reach the taste receptors on the tongue, because a highly viscous food “traps” sugar and salt in its molecular network. That means it would only be representative to compare bulking agents of the same viscosity. That is not easy to do, though, in foods that are composed of many ingredients because all of them have an influence on the overall viscosity of the foodstuff. The taste sensations shown here are therefore a good example of how much research still needs to be invested in exploring the effect of common food ingredients.
Once the corresponding findings are available, however, we can start selecting food ingredients not just based on their price, but also on how they reduce or enhance sweet, salty and fatty taste sensations. This will trigger a revolution in industrial formulations for food products and should be tackled as soon as possible in the interest of promoting the health of large sections of the population.
Food Technology Department at Fulda University of Applied Sciences