Can the development and autolysis of lactic acid bacteria influence the cheese volatile fraction? The case of Grana Padano

In this study, the relationship between the dynamics of the growth and lysis of lactic acid bacteria in Grana Padano cheese and the formation of the volatile flavor compounds during cheese ripening was investigated. The microbial dynamics of Grana Padano cheeses thatwere produced in two different dairies were followed during ripening. The total and cultivable lactic microflora, community composition as determined by length heterogeneity- PCR (LH-PCR), and extent of bacterial lysis using an intracellular enzymatic activity assaywere compared among cheeses after 2, 6 and 13 months of ripening in two dairies. The evolution of whole and lysed microbiota was different between the two dairies. In dairy 2, the number of total cells was higher than that in dairy 1 in all samples, and the number of cells that lysed during ripening was lower. In addition, at the beginning of ripening (2 months), the community structure of the cheese from dairy 2 was more complex and was composed of starter lactic acid bacteria (Lactobacillus helveticus and Lactobacillus delbrueckii) and NSLAB, possibly arising fromraw milk, including Lactobacillus rhamnosus/Lactobacillus casei and Pediococcus acidilactici. On the other hand, the cheese from dairy 1 that ripened for 2 months was mainly composed of the SLAB L. helveticus and L. delbrueckii. An evaluation of the free-DNA fraction through LH-PCR identified those species that had a high degree of lysis. Data on the dynamics of bacterial growth and lysis were evaluated with respect to the volatile profile and the organic acid content of the two cheeses after 13 months of ripening, producing very different results. Cheese from dairy 1 showed a higher content of free fatty acids, particularly those deriving from milk fat lipolysis, benzaldehyde and organic acids, such as pGlu and citric. In contrast, cheese from dairy 2 had a greater amount of ketones, alcohols, hydrocarbons, acetic acid and propionic acid. Based on these results, we can conclude that in the first cheese, the intracellular enzymes thatwere released fromlysiswere mainly involved in aromaformation,whereas in the second cheese, the greater complexity of volatile compounds may be associated with its more complex microbial composition caused from SLAB lysis and NSLAB (mainly L. rhamnosus/L. casei) growth during ripening

Reduction of concentrated feed in dairy cows in the Parmigiano Reggiano area: effects on milk production and quality.

A project of technological research, funded by Emilia Romagna Region and aimed to a higher sustainability of dairy chain, involved an experimental trial testing the effect of a reduction of concentrate feed in Frisona cows producing milk for Parmigiano Reggiano Cheese making. Two groups of 15 cows each, with milk production at 9 days in milk (DIM) of 31.7 and 32.1 kg/d, were fed mixed meadow hay ad libitum and a growing amount of concentrate feed up to 15 kg (C group) or 12 kg (T group) at the peak of lactation (about 60 days). Milk production, milk fat and protein were recorded from each cow at 9, 47, 96, 131, 166, and 207 DIM; fatty acid composition of milk was analysed on 5 pooled samples/group at 47, 131, and 207 DIM. Milk collected from the two groups of cows at day 161 and 168 was used for micro cheese making. Milk production and milk fat were unaffected by diet, whereas milk protein was lower in T cows at 166 (3.18 vs 3.39%; p<.01) and 207 (3.17 vs 3.31%; p<.05) DIM. Fatty acid composition of T milk showed at 47 DIM significantly lower % of MUFA and PUFA, and higher % of SFA, resulting in higher SFA/UFA ratio (1.70 vs 1.38; p<.01). Both n-3 and n-6 fatty acids were significantly lower in T milk at 47 DIM (n-3: 1.21 vs 1.44%; n-6: 4.05 vs 4.57%) and at 131 DIM (n-3: 1.18 vs 1.37%: n-6: 3.89 vs 4.83%). CLA levels were similar in the milk of the two groups. The milk collected for cheese making (60 l/group) had similar chemical and bacteriological composition, with the exception of a higher content of thermophilic Lactobacilli in T milk. Rennet coagulation characteristics showed lower curd firmness at 30’ in T milk (a30: 24.80 vs 29.48 mm; p<.05), whereas the other cheese making traits were not significantly different between the two groups. Bacteriological traits of the ripened cheese (60 days) from the two groups were also similar. The results of this field trial indicate that a reduction of 20% of concentrate feed in the diet of high producing cows did not affect milk amount, milk fat and cheese making traits, but caused a partial deterioration in milk protein, fatty acid composition and rennet coagulation. Further research might evaluate the whole lactation, reproductive performances, nutritional and health status. A part of the results of the research was presented at 6th AITeL Congress (Trento, September 20th 2018)

Study on the influence of pasture on volatile fraction of ewes' dairy products by solid-phase microextraction and gas chromatography-mass spectrometry.

The detection of markers of identification of the geographical origin of food is an attractive challenge and, as far as dairy products are concerned, this paper represents a contribution to this field. In this research the influence of feed on the volatile compound composition was investigated on milk, 2-mo-old cheese (Caciotta), and whey cheese (ricotta) obtained from the same flock of Sarda ewes, under standardized technological conditions. Three different types of pasture (mixture of Lolium perenne and Trifolium squarrosum; rough pasture; Avena sativa) were studied. Solid-phase microextraction combined with gas chromatography-mass spectrometry was used and principal component analysis was applied for statistical evaluation of the data set. The volatile composition was significantly affected by the type of pasture independently of the type of cheese and the ripening period. Moreover, a marker of rough pasture, tentatively identified as (E,E)-3,7,11-tri-methyl-2,4,10-dodecatriene, was detected only in milk and cheeses produced when the ewe flock grazed on that pasture

Comparison of three Different Techniques for the Discrimination of Cheese: Application to the EWE's Cheese.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra

Phospholipids in Milk Fat: Composition, Biological and Technological Significance, and Analytical Strategies

Glycerophospholipids and sphingolipids are quantitatively the most important phospholipids (PLs) in milk. They are located on the milk fat globule membrane (MFGM) and in other membranous material of the skim milk phase. They include principally phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine, while sphingomyelin is the dominant species of sphingolipids There is considerable evidence that PLs have beneficial health effects, such as regulation of the inflammatory reactions, chemopreventive and chemotherapeutic activity on some types of cancer, and inhibition of the cholesterol absorption. PLs show good emulsifying properties and can be used as a delivery system for liposoluble constituents. Due to the amphiphilic characteristics of these molecules, their extraction, separation and detection are critical points in the analytical approach. The extraction by using chloroform and methanol, followed by the determination by high pressure liquid chromatography (HPLC), coupled with evaporative light scattering (ELSD) or mass detector (MS), are the most applied procedures for the PL evaluation. More recently, nuclear magnetic resonance spectrometry (NMR) was also used, but despite it demonstrating high sensitivity, it requires more studies to obtain accurate results. This review is focused on milk fat phospholipids; their composition, biological activity, technological properties, and significance in the structure of milk fat. Different analytical methodologies are also discussed