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Dairy Ingredients
INTRODUCTION
Agro FOOD Industry Hi Tech - vol 24(6) - November/December 2013
Functional foods contain one or more components, such as probiotics and prebiotics, which present the potential to promote the health of the consumer through mechanisms not foreseen in conventional nutrition. Probiotics are defined as viable microorganisms that, when consumed in adequate amounts (106 to 109 viable cells per day), are beneficial to the host (1-3). Among their features, probiotic microorganisms must be normal inhabitants of the human intestinal tract, must survive passage through the upper digestive tract in large numbers, and have beneficial effects when in the intestine. Lactic acid bacteria (LAB) fulfil a number of the outlined criteria for the selection of probiotic strains, including the human intestinal origin, the ability to tolerate acid and bile salts, the low presence of mobilisable antibiotic resistances, as well as the adaptability to technological processes for cheese manufacture (4, 5). It was also shown that strains of Lb. paracasei subsp. paracasei are able to grow in the presence of different prebiotics (6-8), defined as non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or the activity of one or a limited number of bacteria in the colon (9). However, a previous investigation highlighted that the ability of probiotic LAB to use different prebiotics is a strain-specific character (10). Different types of carbohydrates can be classified as prebiotics, including inulin-type fructans, trans-galactooligosaccharides, and lactulose (9). One of the most frequently used prebiotic is inulin, a non-digestible fructan which offers an interesting combination of nutritional properties and technological benefits (11, 12). This prebiotic is a natural non-digestible storage polysaccharide consisting of a chain of fructose molecules with a terminal glucose molecule. It is found in many vegetable products, amongst which chicory roots are considered most suitable for industrial applications. Inulin has the capacity to be a fat substitute, bulking agent, low- calorie sweetener, and texture modifier (13).
Recent studies showed the possibility to use chestnut based products as a good substrate for the growth of LAB (14). The interest in chestnut fruits is due to several functional features, including their gluten free nature, their low fat content, and the presence of some phenolic acids (e.g. gallic and ellagic acid) having antioxidant effects and anti-inflammatory properties (15). Moreover, chestnuts are mainly composed
by starch (amylose 33 % and amylopectin 67 %), which provides positive health effects on gut functions thanks to the bacterial catabolism on amylopectin-derived dextrins into short-chain fatty acids (15).
The dairy sector is the largest functional food market accounting for nearly 33 % of the broad market (16). Different functional dairy products are currently proposed, such as cheeses (17, 18), yogurts, and other fermented and probiotic milks (19-24), yog-ice creams and ice cream (25, 26), starch-based dairy desserts (27), sour cream, and butter cream (28). The success of dairy functional foods can be explained by the general positive image received by consumers, linked to the perception of wellness (functional components able to improve wellbeing), health (chemical and additive free nature of products), and freshness (products kept at refrigeration temperatures and characterized by a relatively short shelf life). Considering the increase in demand for new functional foods, in this study we evaluated the possibility to use Ricotta cheese, a traditional Italian whey protein cheese, as delivery vehicle for probiotics and prebiotics. Ricotta cheese is an unripened, creamy dairy product obtained by heat induced coagulation of whey protein, made mainly from sheep or goat milk, but also from cow and buffalo milk (29). In particular, Ricotta can be made only from whey, or from mixtures of whey and milk (30).
In the light of previous considerations, the aim of this study was to assess the effect of the addition of a probiotic Lb. paracasei subsp. paracasei strain and of two different prebiotics, i.e. inulin and chestnut flour, into Ricotta cheese. The survival of the probiotic strain as well as the sensory, chemical and physical characteristics of the Ricotta cheese were evaluated during the storage at refrigeration temperature.
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