Addition of green and black teas to yoghurt may boost the colour and flavour of the product, without affecting the starter cultures, says a French-Tunisian study.
As unlikely as tea-flavoured yoghurt may seem, findings published in the journal Food Chemistry indicate that addition of green and black tea at a concentration range of 2 to 4 per cent may help formulators tap into growing innovation in the yoghurt market.
A report from Global Industry Analysts says that the entire dairy market continues to benefit from an influx of products launched to cater for health conscious and indulgence seeking consumers, particularly in the emerging markets of Asia.
“The present work is considered as the first report demonstrating that the presence of green and black teas at 2 to 4 per cent did not influence the fermentation of yogurts and the survival of characteristic microorganisms in yogurts during a six-week storage period,” wrote the authors, led by Imène Jaziri from Tunisia’s Institut National de Sciences Appliquées et de Technologie (INSAT).
“Addition of green or black teas in the process milk used for making yogurts is recommended because tea is a natural herbal product with a wide range of beneficial and nutritional properties; this makes this new yogurt a functional food,” they added.
“Furthermore, at a concentration of 2.0 per cent (w/v), which is approximately the strength of a common cup of tea, this may improve the taste of yogurts without having an inhibitory effect on the starter bacteria.”
The researchers investigated the effects of adding green and black teas to milk at the beginning of fermentation with yoghurt starter cultures, S. thermophilus and L. bulgaricus.
Results indicated that the presence of the tea did not affect the characteristic microorganisms of the yogurt during refrigerated storage for six weeks at four degrees Celsius.
Indeed, the authors report that for all tea concentrations used, the starter culture counts reached one billion after six hours of fermentation. Moreover, no effect on lactic acid levels was observed after addition of the teas.
“As a result of these mentioned observations, all the five experimental yogurt formulations fulfilled the legal requirements in terms of acidity and levels of viable starter organisms during the whole storage period, with no significant differences among the various treatments,” wrote the researchers.
“Therefore, tea phenolic compounds in yogurt products will be able to keep their antimicrobial and antioxidant activities and could even constitute novel natural colorants and be considered as ‘functional’,” they added.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin (EC).
The potential health benefits of tea, which have mainly focused on green tea, have been receiving considerable levels of study, with scientists reporting a wide range of effects, including a lower risk of certain cancers, improved heart health, weight loss, and protection against Alzheimer's.
Source: Food Chemistry
Volume 112, Issue 3, Pages 614-620
“Effect of green and black teas (Camellia sinensis L.) on the characteristic microflora of yogurt during fermentation and refrigerated storage”
Authors: I. Jaziri, M. Ben Slama, H. Mhadhbi, M.C. Urdaci, M. Hamdi