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Stevia: A practical guide to product formulations in the South African context

 

There is massive global excitement and interest in stevia, and in South Africa, too, as manufacturers seek to deliver on consumers’ over-arching desire for things ‘natural’. Brian Lanton, MD of Cape Food Ingredients, offers this practical advice on the issues, challenges and application of steviol glycosides.

Recent history

With the 2012 approval of steviol glycosides (>95% purity) in South Africa, more interest has been shown in this sweetener. The reasons are largely because:

  • It is attractive to ‘Marketing’, as it is ‘as natural as cane sugar’ in that it is composed of plant extracts rather than being a created molecule.
  • It has a reasonably acceptable sweetness profile when used properly.
  • It is economically feasible to use compared to the normal ‘sweetener standard cost’, which is that of cane sugar (sucrose). That is, it can offer cost-savings compared to the use of sucrose.

Challenges

As might be expected with a plant extract from various cultivars and with different purification processes, there are significant differences between one ‘stevia’ and another. These taste and sweetness differences relate largely to the extent of isolation of the better-tasting glycosides such as Rebaudoside A [1] and the elimination of those glycosides which have the less attractive taste notes.

However, up to now in the market, the very highly refined glycosides have been relatively expensive (>R1000/kg) while the ‘standard approved’ stevia at 95% total steviol glycosides are much cheaper (<R400/kg). Therefore, the questions are:

  1. Which stevia is the most appropriate to use in product development, as the results  (both in taste and in cost) can be very different from one ‘stevia’ to another; and

2. How to obtain the best taste results for the cheapest cost.

What follows is a brief summary of what we have uncovered in the last two years of development work at our formulation and applications laboratory, mainly in beverages, with a typical ‘stevia’ (>95% glycosides, >50% RebA). I refer to this as ‘stevia’ for convenience – this article does not address formulations with the highly-refined and expensive steviol extracts.

One of the main problems for product development is that ‘Marketing’ is usually ignorant of the properties of this sweetener, and chooses it based on its image (as ‘natural’) rather than for proper use within the parameters of the technical possibilities.

This has already resulted in the launch of several ‘stevia’ products with poor taste quality and this threatens to give stevia a bad name. It is possible that such poorly-formulated products will reduce the market potential of a very acceptable sweetener (when used properly) and, further, do real damage to the fight against obesity which is South Africa’s number one health problem.

Taste profile of >95% steviol glycosides: Using the rule that in the process of partial sugar replacement there should be little or no detectable change in the taste profile of the final product, this type of stevia is capable of a significant reduction in the amount of sucrose used in beverages.

However, stevia has some pronounced ‘off’ tastes when used above a certain level, including lingering sweetness. The key is that stevia should not be used above the level at which such notes become detectable. In our experience, this barrier level is typically found at 2-4 brix (20-40g/litre) of sucrose-equivalent sweetness.

Percentage of sucrose replacement: While 20-40g of sucrose/litre may not seem substantial, the percentage of sucrose replaced depends on the total sweetness of the beverage. For example, in a high-sucrose beverage the replacement may only be 20%, but in a low-sucrose beverage (eg flavoured milks) the replacement may be 50%. In products where only a small amount of sucrose is added, there can be 100% replacement with stevia.

Economics of sucrose replacement: Even at these levels of sucrose replacement, there are significant cost savings at current sucrose and stevia pricing in South Africa, and usually even more cost savings in other African countries where sucrose is typically more expensive or even in periodic scarcity.

For example, with a typical saving of R1 to R2 per case of carbonated soft drinks (CSD), where millions of cases are being sold per annum, the cost savings potential is in millions of rands.

Cost savings are much higher where more expensive sweeteners such as deflavoured juice concentrates or fructose are replaced. Examples are flavoured waters and fruit juice nectars.

Practical ways of extending stevia use

As with all intense sweeteners, the main use of stevia is in beverages and foods with high water content, as the bulking role of sucrose is not crucial in such products and can largely be replaced by water (or high water ingredients such as milk and juices) and some mouthfeel enhancers.

As the taste profile of stevia has its limits, the ability to extend its use and replace more sucrose and therefore realise more health and cost benefits is of key importance.

We have found the following to be particularly useful:

Acids: It is well-established in the literature that citric acid has a ‘fast impact, quick drop-off’ acidic taste profile, and this makes it less suitable as a masking agent for intense sweeteners compared to other acids with longer-lasting acidity. Lactic acid has, for example, been advertised as a ‘masking acid’. Malic and fumaric acids, particularly in combination, are other acids that we have found to be far superior to citric in such applications.

The effects of flavours: It is notable that stevia can be used at higher levels with some flavours than with others. For example, we have found that in the same base of various ranges of CSDs, more sugar could be replaced (20-30%) in certain flavours such as Grape and Pineapple than in others such as Orange or Lem-Lime (10-15% replacement). The latter flavours seem to ‘require’ more sugar to ameliorate or enhance their particular taste profiles.

Another key method of using flavours with stevia is to use subliminal flavours (ie flavours virtually unnoticeable by the casual consumer) to help mask stevia aftertaste. These subliminal flavours can be used with virtually all other flavours, as their taste modification of the primary flavour is either positive or unnoticed.

Where mouthfeel is considered to be missing, this can also be corrected. The use of all of these ingredient tools together results in a balanced formulation that maximises the level of stevia used and so achieves the triple goals of better taste, a cheaper product and the health benefits of sucrose reduction.

Marketing departments will, however, have to be educated in the correct use of sweeteners and stevia in particular, in ways that lead to more balanced decision-making and to optimal results. To use ‘stevia’ incorrectly will result in failed product launches and a bad reputation for this useful sweetener.

Footnote: [1] Even in highly purified steviol glycosides, such as a 97% RebA type, there are differences between producers.

Cape Food Ingredients: www.capefoodingredients.com, T 021 789-1885

Brian Lanton is MD of Cape Food Ingredients, a South African-based company that was a local pioneer in sweetener blending and intense sweetener applications. The company’s R&D facilities are in Cape Town, but it has commercial involvement in most of the major markets in Africa with a portfolio of specialised products including sweetener blends, speciality acids, flavours, enzymes and dairy cultures. A major part of its activity is product formulations for African customers.

This article originally appeared in the May 2013 issue of FST (South African Food Science and Technology magazine, published by SAAFoST)

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