Strategies for improving the nutritional quality of milk and dairy products from different species reared in the Mediterranean area

The aim of the first trial was to evaluate the effects of flaxseed supplementation on the yield and quality of buffalo milk. In particular, the fatty acid profile of milk from buffalo cows subjected to different diets has been investigated. Although buffalo milk is the second most produced milk in the world, and of primary nutritional importance in various parts of the world, few studies have focused on the chemical properties of buffalo milk. The larger size of buffalo fat globules, 5 vs. 3.5 μm, was related to the higher amount of fat in the buffalo milks: 73.4 ± 9.9 vs. 41.3 ± 3.7 g/kg for cow milk. Buffalo milks contained significantly lower amount of polar lipids expressed per gram of lipids (0.26% vs. 0.36%), but significantly higher amount of polar lipids per litre of milk (+26%). For these reasons, considered the interesting potential of this milk and the growing need for functional products it seemed interesting to evaluate the fatty acid composition of buffalo milk obtained from a supplementation of flaxseed in the diet of animals. The experimental design provided for flaxseed supplementation to buffalo dairy cows in mid lactation. Treatments were: (1) no flaxseed supplementation (CO); (2) low flaxseed supplementation (500 g/d; FS500); (3) moderate flaxseed supplementation (1,000g/d; FS1000). Milk protein and casein were affected by flaxseed supplementation resulting lower in flaxseedsupplemented diets. Furthermore, the results revealed that flaxseed supplementation positively affected the milk fatty acids Short-chain fatty acids, in particular C8:0 and C10:0, were the lowest in milk from buffalo cows fed the highest level of flaxseed supplementation. Medium-chain fatty acids were the lowest in FS1000, intermediate in FS500. Long-chain fatty acids were the highest in FS1000, intermediate in FS500 groups, and the lowest in milk from buffalo receiving no flaxseed supplementation. Total conjugated linoleic acid content evidenced the same trend of long-chain fatty acids, with an increase of about 7% in FL500 and of 22% in FL1000 than the control. Atherogenic index, thrombogenic index, and n-6/n-3 were the lowest in FS1000 groups; thrombogenic index and n-6/n-3 were intermediate in milk from animals receiving FS500. Nutritional value of the acidic profile in buffalo milk is influenced by flaxseed supplementation, and its improvement reflects the level of dietary flaxseed supplementation. The objective of this second trial of PhD thesis is to evaluate the sensory profile and consumers’ liking of functional ovine cheese containing probiotic cultures, also observing the action of different strains of probiotic, added to rennet paste for cheesemaking, to assess their ability to produce conjugated linoleic acid (CLA) from free linoleic acid (LA) and Free Amino Acids (FAA), able to positively influence the nutritional and organoletic quality of the cheese. Probiotic are defined as “live microorganisms that, when administred in adeguate amounts, confer a health benefit on the host” (Food and Agricuture Organization of United Nations; World Health Organization-FAO/WHO, 2001). The sensory perception of a food is a very important product characteristic; it is a complex process, which is influenced by many factors, such as content of flavour compounds, the texture, and appearance of the product, but also several characteristics of the individual consuming the product in a certain environment. Aroma development in cheese products is influenced by metabolic activities of cheese bacteria, glycolysis, lipolysis and proteolysis. Flavor compounds in cheese arise from the action of enzymes, from the rennet (substitute), the milk, the (secondary) starter and non-starter bacteria, together with non-enzymatic conversions (Walstra et al., 1993; Kosikowski et al., 1997; Skeie et al., 2000). In cheese making, selected starter cultures are of main importance for controlling flavor formation. In order to respond to the increasing demand for products with improved aroma characteristics, the use of bacterial strains for cheese ripening is considered a very promising method. Ovine cheese was made from ewe’s milk by animals reared in extensive conditions; cheesemaking trials were performed by using rennet paste containing probiotic cells. The experimental test was conducted in a cattle farm where animals (Gentile di Puglia sheep) were reared with a semiextensive system, that provides for the integration of the food ration with concentrated in autumn and winter months. The experimental cheeses are produced using three different rennet pastes lamb rennet in traditional lamb pasta (cheese thus obtained was called cheese control-C), rennet paste lamb containing a mix of Bifidobacterium lactis and Bifidobacterium longum (BB), and cheese manufactured using lamb rennet paste containing Lactobacillus acidophilus (LA).Three experimental cheesemaking were performed for each type of rennet. The rennet had a content of chymosin: pepsin of at 80:20. The probiotic micro-organisms have been incorporated in the rennet paste 24h before each job in a concentration of 109 cfu / g of rennet. The average cell count of probiotic bacteria in the experimental cheese was found to be 7,4x107ufc / g and 7,1x107ufc / g in LA and BB cheeses, respectively, at the end of the vesting period. The cell counts show that the production of cheese from sheep's milk pecorino probiotic Gentile di Puglia was conducted successfully. In the literature it is reported that the minimum dose of probiotics able to really play a beneficial effect on the health of the host is of 108-109 cfu / ml which corresponds to the assumption of 100-g of product containing 106-107 cfu / ml per day (Lourens- Hattingh, 2001). Ovine cheese containing probiotic strains highlighted a more intense proteolysis and a greater level of short chain free fatty acids and conjugated linoleic acid due to the metabolic activity of the adjunct microflora. The sensorial profile of ovine cheese showed lower humidity and gumminess in cheeses containing probiotics as a consequence of differences in the maturing process; furthermore, probiotic cheeses scored higher ratings for salty and pungent attributes. An interaction effect of probiotic, gender, and age of the consumers was detected in the perceived and the expected liking. The higher rate of expected liking in all experimental cheeses is attributed to the information given, regarding not only the presence of probiotic strains but also the farming conditions and cheesemaking technology.