The future is green
If you were inventing the ideal functional ingredient, you might start with something that guards against cancer and offers cardiovascular protection. But why not add some fat-burning properties that could aid weight management while you're at it? And if you want even more, let's throw in gum protection and fresh breath for good measure. Better still, let's make it natural so it sounds appealing on today's cleaner food labels. Such a dream product may sound improbable but it's no fantasy. You've just reinvented green tea extract (GTE).According to Taiyo, the world's biggest manufacturer of GTE, green tea has demonstrated antioxidant, anticarcinogenic, antimutagenic, antibacterial, antifungal, antiviral, anticariogenic, thermogenic, kidney protecting, deodorising and blood glucose and blood-lipid-controlling properties.
Furthermore, unlike some natural extracts, the science is there to back up the major claims, with more than 1,500 papers published on green tea in research journals in the last five years.
Not surprisingly, this has led to a lot of interest in GTE, with Frost & Sullivan valuing the market at £44M and predicting 13% growth by 2015. This includes supplements and cosmetics as well as food and beverage.
Mintel reports that the number of food and beverage launches featuring green tea has been running at well over 200 a year across Europe, with drinks accounting for roughly 80% of the new products.
And it's not just niche producers who are getting in on the act. Coca-Cola added green tea citrus flavoured versions to its Nestea RTD iced tea range in May 2008, boasting 50% more antioxidants than previous products, while a tie-up with Nestlé has led to the rather more controversial Enviga product in the US.
Polyphenol promise
The beneficial properties of green tea stem largely from its polyphenol content, which gives it those all-important antioxidant properties. The polyphenols include catechins, flavones, phenolic acids and anthocyanins. Of all the compounds included in the line-up, however, the most bioactive and important is epigallocatechin gallate (EGCG).
Other compounds naturally found in tea can also play a role in the functionality of GTE. For example, Taiyo has been strongly promoting the benefits of the amino acid L-Theanine, which it bills as a natural stress reliever that improves sleep and boosts concentration.
China is by far the biggest source of green tea and GTE, although there are companies engaged in processing GTE elsewhere, including Europe.
Producing extracts
A standard GTE is typically produced by solvent extraction, "Tea catechins are structurally primarily flavanols and form 20 to 30% of the dry weight of green tea," says Farhana Rahman, senior development technologist for UK-based supplier, William Ransom.
"A normal extract is what you obtain when green tea is extracted using a solvent such as ethanol. Purified extracts are a separate category where the concentration of polyphenols is selectively enhanced based on the end use."
So, for example, William Ransom GTE products include a strong green tea infusion with 2% by weight of catechins, soft extracts standardised at 20%, dry extracts containing at least 30% and purified extracts with 90% total polyphenols.
Taiyo's Sunphenon range includes an even more bewildering array of GTE grades, offering different combinations of polyphenols, catechins, EGCG and caffeine.
On the other hand, DSM Nutritional Products, which is another major player with facilities in China, has chosen to concentrate its efforts solely on offering Teavigo, which is one of the most highly purified, caffeine-free EGCG products on the market.
Extracts are generally soluble and heat stable under normal processing conditions. They are sensitive to oxygen and free radicals, but that's exactly what gives them their antioxidant properties. The main challenges of formulating products with GTE are colour and taste.
Extracts can range from green or brown through to colourless, depending on the purity. Although the strong colour of less purified extracts can a drawback in some applications, it can be an advantage in others.
For example, Taiyo produces a separate range of bright green, tea-based products known as Matcha, which are specifically used to colour products such as cakes, biscuits and chocolate, including Nestlé's green Kit Kats in Japan.
Bitter pill
Taste is the other potential issue, since GTE can also be bitter. Taiyo specifically markets 'LB' low-bitterness versions within its Sunphenon GTE range, but a certain amount of bitterness remains inevitable.
Unlike colour, Rahman says that increasing the purity of the extracts cannot get around the problem of taste: "The catechins impart the bitter, astringent taste and therefore the higher the purity, the higher the bitterness."
"Catechins per se are bitter," agrees Frank Thielecke, global science manager for DSM Nutritional Products. "So the success of a formulation really depends on the skills of the experts and the food matrix. Near-water applications are more tricky than, say, a smoothie."
On the other hand, Thielecke maintains that the purity of Teavigo makes it easier to use in many applications. "It's suitable for a wider range of applications because the purity gives Teavigo sensory advantages like less taste and colour, which can limit the application profile of other GTEs.
For example, other catechins and caffeine also add to the bitterness of some extracts," he says.
Beverages and confectionery
Everyone seems in broad agreement about the most promising product areas for GTE in food and drink. "Beverage and confectionery are the two key areas," says Joy Thomas, business manager for health and food at the Cornelius Group, which is the UK distributor for Taiyo.
Thomas highlights chews and gums as particularly promising, thanks to the oral health benefits of GTE.
"I think beverages and snack bars are two very promising applications and apply across many geographical markets," adds Rahman.
But how does incorporating the extracts into different matrices affect their bioavailability and health-giving properties? "This area needs to be further explored," says Rahman.
"Past research however indicates that some catechins, and particularly EGCG, bind with proteins present in the food matrix and therefore become unavailable."
Thielecke is more optimistic. "A lot of the clinical trials were done using green tea infusions or combined GTE with a meal. If you have EGCG in a blend of polyphenols or a food matrix, the bioavailability may be reduced but the physiological effects seem to remain," he says.
Bioavailability remains a vexed question, and one that will need answering if food manufacturers want to make the strongest possible health claims.
New regulations on nutrition and health claims are due to come into force across Europe next year, making manufacturers provide more evidence than ever before to back up any functional claims they make for their products.
For example, recent research has raised the possibility that adding milk might adversely affect the vascular benefits of tea. "The protein in dairy might interfere with the uptake of catechins but we don't know how," says Roberta Re, team leader in the nutrition and health department at Leatherhead Food International (LFI).
"The uptake might just be delayed, for instance, so you might still get the benefit in the end."
Technical exploration
LFI is currently in the process of setting up a project to provide some answers. "We're looking at a collaborative project that will involve suppliers and manufacturers," says Re. "We want to look at the effect of the food matrix on catechins and how the uptake is affected. We'll give people GTE in different types of food product."
LFI plans specifically to look at the bioavailability of GTE in hot and cold drinks, as well green tea powder in a cereal-based product and a dairy-based product. The aim is to get the project up and running by the end of the year.
In the meantime, there remains a lot of uncertainty about how the EU Nutrition and Health Claims Regulation will affect the claims made for products containing green tea. "It's a very complicated story," says Re. "It depends on the type of claim you want to make and it really is a minefield."
"Suppliers like Taiyo have put forward their claims for the approved list and now it's a bit of a waiting game," says Thomas.
While the major ingredient suppliers may have submitted their claims, what that will translate into for the food and beverage manufacturers remains to be seen.
"The manufacturers of the raw materials can do a certain amount of preliminary work, but the health benefits of a food product really depend on the final formulation," she says.
"Taiyo is really good at providing formulation advice and information on the basic research, but this will only take manufacturers so far."
