Strains of Lactobacillus added to the cheese resulted in the formation and release of proteins that are biologically active, such as angiotensin converting enzyme (ACE)-inhibitory peptides, report the researchers in the Journal of Food Science .
ACE inhibitors work by inhibiting the conversion of angiotensin I to the potent vasoconstrictor, angiotensin II, thereby improving blood flow and blood pressure.
ACE inhibitors made by drug companies have been found to be beneficial in treating hypertension, particularly in patients with type-1 or type-2 diabetes, and also appear to provide good cardiovascular and renal protection.
Pharmaceutical ACE-inhibitors do however have side effects.
"Probiotic L. acidophilus L10 was able to remain viable in cheddar cheeses after 24 wk of ripening at four, eight, and 12 degrees Celsius with improved ACE-inhibitory activity," wrote the researchers, led by Nagendra Shah form Victoria University in Melbourne.
"The results of this study indicated that addition of probiotic L. acidophilus L10 into cheddar cheeses could have potential to improve the quality of cheeses and health status of the product through increased ACE-inhibitory activity."
In the UK alone there are an estimated 10m people with hypertension, defined as having blood pressure higher than 140/90 mmHg.
The condition is a major risk factor for cardiovascular disease (CVD), which causes almost 50 per cent of deaths in Europe, and is reported to cost the EU economy an estimated €169bn ($202bn) per year.
New results
The Australian researchers produced three forms of cheddar cheese: one using only a lactococci starter culture (control); one with the starter culture plus Lactobacillus acidophilus L10 (Lafti L10, DSM Food Specialties); and one with the starter plus L. acidophilus L10 and L. helveticus H100.
Probiotic cell counts remained above 106 colony forming units (CFU) per gram after the 24-week ripening period at all of the temperatures studied (four, eight, and 12 degrees Celsius).
Higher levels of ACE-inhibition were observed for the cheeses ripened at higher temperatures, but the ACE-inhibitory activities were not significantly different, reported the researchers.
Increased ACE-inhibition was associated with improvements in proteolysis (protein splitting) of the cheeses Increases in levels of lactic, acetic, and propionic acids - reported to adversely affect flavour and aroma when present in excess - in the probiotic cheeses were also observed, relative to the control cheese after 24 weeks, showing that some consideration must be given to finding a balance between enhancing growth of the nonstarter lactic acid bacteria (NSLAB) and boosting the health aspects of the cheese.
"It has been recommended that a product contain at least 107 cells per gram or milliliter of food to provide health effects," wrote the researchers.
"It is also possible that the beneficial health effects of cheese can be increased based on the peptides released as a result of proteolysis during ripening," they added.
State of the market Dairy foods, including fermented milks and yoghurts, are among the best accepted food carriers for probiotic cultures.
However, companies are increasingly looking at other ways of using probiotics, which are frequently limited to refrigerated foods as they are sensitive to heat, humidity and other harsh conditions.
Last year a cheese containing a Chr.
Hansen probiotic was launched in Italy, a move explained by the company as due in part to the fact overall consumption of cheese in Italy reached 1,368,000 tons (23.4 kg per capita) in 2005, growing by 2.18 per cent from the previous year.
Moreover, a Lafti probiotic cheese was launched in the UK market in 2006 by Butler's Cheese and sold in Walmart-owned ASDA supermarkets, while Danisco Cultures has been looking at, amongst other things, a shaped probiotic-cheese slice, suitable for inclusion in a child's lunchbox.
Arla Foods launched and a probiotic cheese containing the Lactobacillus casei strain F19 in the US, and the probiotic is present in products in Scandinavia under the name of Cultura.
However, the market for 'functional cheese' is still small.
In Britain, for example, David Bird, a food and drink industry analyst at Mintel, said in May 2007 that, while the market may grow in the long term, it is expected to stay "very niche for quite a while" .
While many insiders see added-value and functional product development as priority areas for research funding for the cheese industry, progress in functional categories may be hindered by cheese's unhealthy public image.
It was recently included in a ban on 'junk food' television adverts aimed at children.
Proteins from milk have already been investigated for their potential blood pressure-improving effects.
Puleva Biotech is looking at ACE-inhibiting hydrolysed caseins from goat's milk, for example, as novel ingredients to prevent the development of high blood pressure, and have already shown efficacy in a rat study.
"Most of the studies pertaining to production of the ACE-inhibitory peptides were performed in fermented milk or yogurt with proteolytic strains of lactic acid bacteria (LAB), mainly L. helveticus ," added the Australian researchers.
"Only a few studies have investigated the release of ACE-inhibitory peptides in cheeses made with the addition of probiotic bacteria."
Source: Journal of Food Science (Blackwell) Published on-line ahead of print, OnlineEarly Articles , doi:10.1111/j.1750-3841.2008.00689.x "Influence of Probiotic Lactobacillus acidophilus and L. helveticus on Proteolysis, Organic Acid Profiles, and ACE-Inhibitory Activity of cheddar Cheeses Ripened at 4, 8, and 12 degrees C" Authors: L. Ong, N.P. Shah