Reduction of pH key to green tea enriched biscuit quality, finds new study

By Jane Byrne

- Last updated on GMT

Related tags: Green tea

Retention of green tea extracts in biscuits is improved by a reduction in the pH of the dough, finds new research looking at the stability of different catechins when fortifying baked goods.

The Singapore based researchers, who published their conclusions in Food Chemistry, ​claim adding green tea extract (GTE) in powder form to biscuits can not only improve their shelf life by preventing rancidity, but could also help manufacturers tap into the growing trend for healthier snacking.

The authors said their study exploring the stability of catechins during biscuit manufacture was prompted by the fact that commercial utilisation of tea or tea products in these baked goods is very limited, and, that, furthermore, no scientific data is available on the function of green tea extracts on biscuit quality.

Tea antioxidants have drawn increased attention in recent years because of their potential health benefits, not only as an antioxidant agent but also as anti-arteriosclerotic, anti-carcinogenic, and antimicrobial agents. Four major tea catechins have been identified as (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG), (−)-epicatechin (EC) and (−)-epicatechin gallate (ECG).

The study

GTEs at 150, 200, and 300 mg per 100 g of flour were formulated, explained the team.

And they said that a method was developed for the separation and quantification of tea catechins in GTE, dough, and biscuit samples using a RP-HPLC system. The stability of (−)-EGCG and (−)-ECG was determined at an interval of every 2 minutes during baking, added the authors.

They concluded that the amount of (−)-EGCG and (−)-ECG was maximum in the dough and decreased as baking progressed. While they found that the level of retention of EGCG and ECG increased in the dough and biscuit as the initial concentration of GTE was raised from 150 mg to 200 mg and 300 mg per 100 g of flour.

“The results obtained showed that green tea catechins were relatively stable in dough. The stability of (−)-EGCG also increased as pH of the dough was reduced and made less alkaline,” ​found the scientists.

The team, in order to determine whether the pH of the system was responsible for the loss of catechins in dough, prepared a control sample with 200 mg GTE per 100 g flour without the addition of any material that could contribute to the alkalinity of the product such as baking powder, sodium bicarbonate, and ammonium bicarbonate.

The researchers found that the amount of EGCG and ECG present in this dough was 60.4 ± 1.32 per cent and 68.5 ± 1.85 per cent respectively compared to 43.8 ± 0.50 and 71.1 ± 3.74 per cent respectively for standard biscuit dough with the same level of GTE incorporation.

“Hence, by reducing the pH, there was a statistically significant increase in the retention of EGCG in dough,”​ they added.

The authors further investigated any loss of catechins due to epimerisation, comparing the sum totals of (−)-EGCG + (−)-GCG, and (−)-ECG + (−)-CG from both dough types.

“It was found that the sum of (−)-EGCG + (−)-GCG from the dough without any alkalinity-inducing ingredients was higher than that from the normal dough. However, the sums of (−)-ECG + (−)-CG from both the doughs were statistically the same.

This confirms that the loss of (−)-EGCG was partly due to degradation because of higher pH, and not epimerisation,”​ they stressed.

Source: Food Chemistry
Published online ahead of print: doi:10.1016/j.foodchem.2010.1.044
Title: A stability study of green tea catechins during the biscuit making process
Authors: A. Sharma, W. Zhou

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