Volatile Compounds In Cheeses Research Articles

Characterization of the volatile compound profile of artisanal Minas cheese from different regions

Artisanal Minas cheese (AMC) is a product with great economic, historical, and cultural value, and the final organoleptic characteristics of AMC can be influenced by soil and climate factors at the production site (terroir). This study aimed to evaluate the profile of volatile compounds in cheeses from seven certified producing regions in Minas Gerais, Brazil, to characterize the volatile compounds according to their origin. A total of 78 samples were obtained from producers registered with the health certification body (Instituto Mineiro de Agropecuária), and the health requirements, minimum ripening time, and characteristic production methods of the cheeses from each region were followed. In general, a total of 166 compounds were identified, which were divided into several chemical groups, including aldehydes (20), ketones (17), carboxylic acids (20), terpenes (6), esters (57), hydrocarbons (15), and alcohols (31). The terpenes α-pinene and caryophyllene-oxide were possible plant markers for cheeses from the Canastra and Serro regions, as these compounds were not identified in cheeses from the other regions. For cheeses from different regions, interactions between some origin-related compounds were verified, which may help establish guidelines and standards for chemical compounds at different production sites, as there are differences between the profiles of volatile compounds and the region.

Microbial communities and volatile profile of Queijo de Azeitão PDO cheese, a traditional Mediterranean thistle-curdled cheese from Portugal

The production of ovine or caprine milk cheeses with thistle rennet is a common practice in the Mediterranean basin. The aim of the present study was to obtain information on bacteria and yeast communities harboured by Queijo de Azeitão PDO cheese through viable counting and, for the first time, via metataxonomic analysis. Moreover, solid phase microextraction (SPME) technique was applied to characterize Queijo de Azeitão PDO cheese volatile compounds. Nine cheese samples were collected from three different artisan producers located in Portugal. The results of physico-chemical analyses showed significant differences between producers, with mean values ranging from 5.40 ± 0.25 (Producer 1) to 6.00 ± 0.22 (Producer 2). As for TTA, Producer 1 showed the highest mean value attesting at 18.04 ± 6.57 mL of 0.1 M NaOH used to reach pH 8.3. Regarding lactic acid concentration, Producer 1 showed the highest mean value attesting at 0.488 ± 0.106 g 100 g−1, whereas, for acetic acid, no significant differences were evidenced among producers with values comprised between 0.141 ± 0.021 g 100 g−1 and 0.245 ± 0.016 g 100 g−1. No significant differences were observed between overall mean values of the three producers for viable counts of presumptive lactococci, thermophilic cocci, presumptive lactobacilli, thermophilic lactobacilli and total mesophilic aerobes with values in the order of 7–8 log cfu g−1. Moreover, no significant differences were evidenced for viable counts of coagulase-negative cocci, enterococci, Enterobacteriaceae and Pseudomonadaceae. As for eumycetes, cheeses from Producer 1 showed the lowest mean value (2.78 ± 2.42 log cfu g−1) in respect with values detected in cheeses from Producer 2 and 3. Concerning microbiota and mycobiota of the analyzed cheeses, the alpha diversity index did not show any significant difference between the three producers in terms of composition and complexity of the microbial population. A simple composition was apparently shared by the three producers, whose cheese manufactures were dominated by the presence of Leuconostoc mesenteroides (37% of the relative frequency in average), Lactococcus lactis (29%), Lacticaseibacillus zeae (4.7%), Lentilactobacillus kefiri (4.4%), Serratia spp. (3.5%), Lactiplantibacillus plantarum (2.7%), and Latilactobacillus sakei (2.5%). The mycobiota composition showed the neat dominance of Yarrowia lipolytica (46.7% of the relative frequency in average), followed by Candida ethanolica (13.6%), Kurtzmaniella zeylanoides (9.4%), Geotrichum candidum (8.8%), Galactomyces geotrichum (8.7%), Kluyveromyces lactis (3.5%), and Geotrichum silvicola (2.7%). The volatile profile analysis allowed 24 different compounds to be identified: 7 acids, 7 esters, 4 alcohols, 3 ketones, 2 aromatic hydrocarbons, and 1 aldehyde. The most represented volatile organic compounds (VOCs) were 2-butanone, butanoic acid and hexanoic acid. A positive correlation between Len. kefiri and hexanoic acid and isopentyl isobutyrate was observed (P < 0.05), whereas Y. lipolytica displayed the highest number of positive correlations with 3-methyl-butanal, 2-pentanone and 2-pentanol (P < 0.05). To the authors' knowledge, this is the very first detection of Len. kefiri in a raw ewe’s milk cheese coagulated with vegetable rennet.

Study of the Compositional, Microbiological, Biochemical, and Volatile Profile of Red-Veined Cheese, an Internal Monascus-Ripened Variety.

Red-Veined Cheese is an experimental internal mold-ripened cheese using red koji powder as the red starter. The objective of this study was to characterize the physicochemical parameters, microorganisms, proteolysis, lipolysis, and volatile profile of the cheese during 33 days of ripening. The gross composition was 56.7% (w/w) for total solids, 45.8% (w/w) for fat-in-dry matter, 2.58% (w/w) for salt content and 37.8% (w/w) for protein. The pH increased from 4.88 to 5.23 during ripening. The Monascus density first rose and then fell, while total mesophilic bacteria count declined steadily throughout the maturation. Proteolysis degree in experimental group was significantly higher than in control group without inoculation of red koji powder. Analysis of the fatty acid profile showed that the internal Monascus-fermentation also promoted lipolysis. A total of 63 volatile compounds, including 12 ketones, 14 alcohols, 15 acids, 13 esters, 5 aldehydes, 3 lactones and 1 phenol, were identified by gas chromatography-mass spectrometry (GC–MS) coupled with headspace solid-phase microextraction (HS-SPME). The main chemical groups of volatile compounds were ketones, alcohols, acids and esters whereas aldehydes, lactones, and phenols represented only minor components. At the end of ripening, the levels of ketones, alcohols, esters were significantly higher in the experimental cheese compared with the control. Our results therefore show that the internal Monascus-fermentation is not only a suitable technology to form red veins in the paste but also an effective method to impact the composition of volatile compounds in cheese, which can thus distinguish it from other internal mold-ripened cheeses and surface-ripened Monascus-fermented cheese.

Impact of salting and ripening temperatures on late blowing defect in Valtellina Casera PDO cheese

Clostridial contamination of raw milk can cause the late blowing defect (LBD) in semi-hard and hard cheeses. In this study we have evaluated the influence of salting and ripening temperatures on LBD appearance in Valtellina Casera PDO cheese. Four cheese lots were brined at two different temperatures (8 and 13 °C) and successively ripened at 8 or 13 °C for 90 days. To evaluate the spore content a modified most probable number (MPN) method was used. The brining temperature of 8 °C seemed to prevent clostridial germination. During the ripening we detected LBD symptoms in all the cheeses aged at 13 °C, while no defects were observed in those placed at 8 °C. Clostridium tyrobutyricum resulted to be the main cause of LBD and its development was temperature-dependent. Volatilome analysis highlighted rancid volatile compounds in cheeses ripened at 13 °C. A combination of salting and ripening temperatures resulted to be an effective strategy to prevent and control the LBD in cheeses. A brine temperature of 13 °C followed by an aging at 8 °C inhibited the germination of C. tyrobutyricum spores during brining and subsequent germination during ripening.

Impact of packaging properties on the physical‐chemical‐microbiological‐sensory characteristics of Ricotta cheese during storage

Ricotta is a highly perishable cheese of which shelf‐life is strongly influenced by the properties of packages in which it is stored. Four plastic packages currently in use in Italy (IT), Romania (RO), Slovenia (SLO), and Spain (SP) are characterized in term of structure, barrier, and antimicrobial properties, and their efficiency in the ricotta storage at 4°C is assessed. Differential scanning calorimetry and Fourier‐transform infrared spectroscopy analysis indicate that the IT and SP packages are made of low‐density polyethylene and the RO and SLO packages consist of polyethylene and polyamide 6. Permeability to the water vapour and oxygen transmission rate vary as follows: IT&gt;SLO &gt; RO &gt; SP and SP &gt; IT&gt;RO &gt; SLO, respectively. The SP package expressed the highest antimicrobial inhibition whilst the IT package the lowest. The maximum amounts of volatile compounds in cheese were reached after 3 days in the IT and SP packages and after 6 days in the SLO and RO packages. The score 2.8 for cheese overall acceptability was exceeded after 7 days in the IT, RO, and SP packages and 6 days in the SLO package. Barrier properties of packages significantly influence the shelf‐life of ricotta. Low barrier properties resulted in high level of oxygen and water vapours inside the headspace of packages ultimately favour the microbial development. The simultaneous compliance of microbiological safety level and overall acceptability score gives ricotta a shelf‐life of 3 days in the IT, RO, and SP packages and 1 day in the SLO package.

Survival of Kluyveromyces lactis and Torulaspora delbrueckii to simulated gastrointestinal conditions and their use as single and mixed inoculum for cheese production.

The demand for new probiotic products has shown recent increases alongside a growing interest in studying starter cultures of cheeses. This study thus aims to evaluate the ability to survive under simulated gastrointestinal conditions and impact of Torulaspora delbrueckii B14 and Kluyveromyces lactis B10 as single and mixed inocula for cheese production. These two yeast strains were subjected to simulated gastrointestinal tracts and tested for self-aggregation, hydrophobicity, pathogen inhibition, antibiotic resistance, and β-galactosidase production. The yeast strains were also assessed for their ability to survive in different NaCl concentrations (2.5%, 5%, and 10% w/v), multiple temperatures (4 °C and 40 °C), and used as single and mixed starter cultures for cheese production. Yeasts population levels were monitored by YPD plating and MALDI-TOF and metabolites were analyzed by HPLC and GC-MS over the course of the 21 days cheese maturation process. T. delbrueckii B14 and K. lactis B10 both showed >80% viability after the passage through the simulated gastrointestinal tract, had self-aggregation rates >90%, and displayed β-galactosidase activities of 0.35 U/g and 0.53 U/g, respectively. Both yeasts survived at 2.5%, 5%, and 10% NaCl for 21 days and showed growth at 4 °C. In cheese, the single inoculum of K. lactis B10 and mixed inoculum showed the highest levels of lactose consumption. HS-SPME GC-MS analysis of cheese samples allowed the identification of 38 volatile compounds. The highest concentrations of most of these compounds were observed after 21 days of maturation for the cheese produced with mixed inoculum. The most abundant acids detected were hexanoic and decanoic acid; the most abundant alcohols were 2,3-butanediol, 2-phenylethanol and isoamyl alcohol, and the most prevalent ester compounds were isoamyl acetate and phenethyl acetate. Our results therefore show that T. delbrueckii B14 and K. lactis B10 are interesting yeasts for further studies in the context of probiotics and positively impact the composition of desirable volatile compounds in cheeses, particularly when used as mixed inoculum.

Volatile compounds and biogenic amines during the ripening of mold‐ripened Civil cheese manufactured using three different strains of Penicillium roqueforti

AbstractThree different strains of Penicillium roqueforti were used for the manufacture of mold‐ripened Civil cheese and these cheeses were ripened at 4 and 10 °C for 90 days. Sixty‐five volatile compounds were identified in the volatile fractions of the cheeses. The concentration of volatile compounds in cheeses was significantly affected ripening time temperature and by mold strains a lesser extent. 3‐Methyl‐1‐butanol, 2‐nonanol, methyl dodecanoate, butanoic acid, and decanoic acid were the most frequently identified volatiles. Tryptamine, 2‐phenylethylamine, putrescine, cadaverine, tyramine, spermidine, and spermine were also found. The most abundant biogenic amine was cadaverine. The formation of biogenic amines was significantly influenced by strain, ripening time, and temperature. The biogenic amine content was found to be between 2.41 and 228.94 μg/g cheese. Ripening temperature and ripening time significantly influenced the formation of volatile compounds and biogenic amines.Practical applicationsMoldy Civil is a traditional cheese variety produced in the eastern Anatolian region of Turkey and it is protected by geographical indication by Turkish Patent and Trademark Office (TURKPATENT) by 2010. It is manufactured using skimmed milk which is spontaneously acidified with native lactic acid bacteria and also the addition of preacidified whey. Three strains of P. roqueforti was used in Moldy Civil cheese‐making and strains of the mold changed the volatile profiles and the levels of biogenic amines less than ripening time and temperature. Methyl ketones and alcohols were the dominant groups in volatiles, while cadaverine was found to be principal biogenic amine in Moldy Civil cheese. Use of P. roqueforti strains contributed to the formation of the volatile fraction of the cheese; however, the level of biogenic amines changed by P. roqueforti strains a lesser extent.

Fat reduction and whey protein concentrate addition alter the concentration of volatile compounds during Prato cheese ripening

The impact of fat reduction and the addition of whey protein concentrate (WPC) on the volatile compounds profile of Prato cheese was evaluated for 210 days of storage at 12 °C. Full fatPrato cheese, Prato cheese with fat reduction and reduced fatPrato cheese with 0.5% (w/v) WPC were made, and replicated on a different day. Cheese volatile compounds were extracted by solid phase microextraction (SPME) and separated, identified and quantified by gas chromatography coupled to a mass spectrometry detector (GC-MS). Fat reduction and the WPC addition resulted in lower concentrations of compounds derived from lipolysis and free fatty acid catabolism. Fat reduction generated higher levels of diacetyl and acetoin, both from the citrate metabolism, at days 5 and 30. A similar pattern was observed for sulfur compounds derived from the catabolism of free amino acids, at day 120. Higher levels of diacetyl (day15), dimethyl disulfide (days 150–180) and dimethyl trisulphide (days 150–210) were found for cheese with WPC. These differences might have occurred due to alterations in the structure and polarity of the protein matrix caused by fat reduction and the WPC addition.

Effects of n-3 fatty acid sources on butter and hard cooked cheese; technological properties and sensory quality

The effects on milk, butter and hard cooked cheese of new n-3 fatty acid (FA) sources in cows' corn silage-based diets – microalgae DHA Gold® (ALG), sieved extruded linseed (SEL) and their combination (SEL/ALG) – were assessed. Butter processing from ALG and SEL/ALG cream was not possible. Butter from SEL had less yellow colour and tended to be softer, with less rancid flavour and odour but stronger cream flavour. For SEL/ALG, cheese yield before brining was higher, but fat content in dry matter and curd dry matter were lower. For ALG and SEL/ALG, cheeses were evaluated as less coloured, more open, less firm, less elastic, more grainy and spicy. Cheese volatile compounds were affected by cows’ diet; higher concentrations of compounds from FA oxidation and amino acid catabolism were observed with the addition of microalgae DHA Gold®. Flavour profiles of cheeses were slightly affected by this addition, but no off-flavour was perceived.

Effect of high-pressure treatments on proteolysis, volatile compounds, texture, colour, and sensory characteristics of semi-hard raw ewe milk cheese

High pressure (HP) offers potential industrial applications in cheese preservation, but it is essential to provide knowledge concerning their effects on the ripening process and sensory characteristics. In this study, we investigated the effect of different HP treatments (200–500MPa at 14°C for 10min on day 7) on proteolysis, texture, colour, volatile compounds and sensory characteristics of semi-hard raw ewe milk cheese. HP treatments did not affect pH or dry matter values of 60-day-old cheeses. Treatments at pressure levels up to 400MPa led to significant (P<0.01) increases in the total free amino acids (FAA) content at 60days, compared to control cheese, although the cell-free aminopeptidase activity was lower. HP retarded the formation of some volatile compounds in cheeses, the number of compounds affected by HP being higher as the pressure level increased. Cheeses pressurized at 300–500MPa had lower levels of 2-butanone, 2-butanol, 2-propen-1-ol, 1-butanol and acetic acid than control cheese, cheeses pressurized at 400–500MPa lower levels of 1-propanol, 2-pentanol, and butyric and hexanoic acids, and cheeses pressurized at 500MPa lower levels of ethanol, 3-methyl-1-butanol and 3-methyl-2-buten-1-ol. All HP-treated cheeses showed higher fracturability values, and higher Hue angle and lower a* values than control cheese. Despite the differences detected by instrumental analyses between HP-cheeses and control cheese, few significant differences were found between the sensory characteristics of HP-cheeses and control cheese. Only the pressurization of cheese at 500MPa affected significantly (P<0.01) some of the sensory characteristics, with a negative effect on taste intensity but a positive effect on aroma quality.In summary, HP treatments at 200 and 300MPa showed the mildest effects on the characteristics of semi-hard raw ewe milk cheese. HP treatment of this cheese variety at 300, 400 and 500MPa prevented late blowing defect caused by Clostridium tyrobutyricum (Ávila et al., 2016, Food Microbiol. 60, 165–173). Thus, it may be concluded that HP treatment at 300MPa is the most adequate procedure, able to prevent late blowing with minimum changes in cheese characteristics.

Lactobacillus delbrueckii subsp. lactis as a starter culture significantly affects the dynamics of volatile compound profiles of hard cooked cheeses

Lactobacillus delbrueckii (LD) is a species usually found in raw milk hard cooked cheeses. Present in raw milk, it grows in cheeses during ripening, but it can also be added in large concentrations with acidifying starter cultures. Its role in cheese proteolysis has been largely demonstrated, but its role in the formation of volatile compounds in cheeses remains to be documented. For this purpose, 16 experimental hard cooked cheeses were made from raw milk using adjunct cultures made up of Streptococcus thermophilus and Lactobacillus helveticus with the addition or not of LD, and ripened for 184 days. Bacterial populations and volatile compounds were monitored throughout ripening. The LD addition affected the early growth of the starters but not the dynamics of the native microbiota. LD had a major effect on proteolysis and on the composition of volatile compounds. Of the 85 volatile compounds identified in the cheeses, 6 of the 7 acids, 10 of the 16 aldehydes, 11 of the 17 alcohols, 10 of the 17 ketones, 10 of the 23 esters, and 4 of the 5 sulphur compounds were affected by the LD addition at one or more stages of ripening. At the end of ripening, levels of the 31 compounds affected by LD were higher in the cheeses with LD added, except one secondary alcohol and 2 methyl-ketones. The question of the effective involvement of LD in these observations, whether due to the metabolic activity of LD or interactions with other microbial populations, is raised.

From cow to cheese: genetic parameters of the flavour fingerprint of cheese investigated by direct-injection mass spectrometry (PTR-ToF-MS).

BackgroundVolatile organic compounds determine important quality traits in cheese. The aim of this work was to infer genetic parameters of the profile of volatile compounds in cheese as revealed by direct-injection mass spectrometry of the headspace gas from model cheeses that were produced from milk samples from individual cows.MethodsA total of 1075 model cheeses were produced using raw whole-milk samples that were collected from individual Brown Swiss cows. Single spectrometry peaks and a combination of these peaks obtained by principal component analysis (PCA) were analysed. Using a Bayesian approach, we estimated genetic parameters for 240 individual spectrometry peaks and for the first ten principal components (PC) extracted from them.ResultsOur results show that there is some genetic variability in the volatile compound fingerprint of these model cheeses. Most peaks were characterized by a substantial heritability and for about one quarter of the peaks, heritability (up to 21.6%) was higher than that of the best PC. Intra-herd heritability of the PC ranged from 3.6 to 10.2% and was similar to heritabilities estimated for milk fat, specific fatty acids, somatic cell count and some coagulation parameters in the same population. We also calculated phenotypic correlations between PC (around zero as expected), the corresponding genetic correlations (from −0.79 to 0.86) and correlations between herds and sampling-processing dates (from −0.88 to 0.66), which confirmed that there is a relationship between cheese flavour and the dairy system in which cows are reared.ConclusionsThis work reveals the existence of a link between the cow’s genetic background and the profile of volatile compounds in cheese. Analysis of the relationships between the volatile organic compound (VOC) content and the sensory characteristics of cheese as perceived by the consumer, and of the genetic basis of these relationships could generate new knowledge that would open up the possibility of controlling and improving the sensory properties of cheese through genetic selection of cows. More detailed investigations are necessary to connect VOC with the sensory properties of cheese and gain a better understanding of the significance of these new phenotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12711-016-0263-4) contains supplementary material, which is available to authorized users.

The role of the canonical biplot method in the study of volatile compounds in cheeses of variable composition

The canonical biplot method (CB) is used to determine the discriminatory power of volatile chemical compounds in cheese. These volatile compounds were used as variables in order to differentiate among 6 groups or populations of cheeses (combinations of two seasons (winter and summer) with 3 types of cheese (cow, sheep and goat’s milk). We analyzed a total of 17 volatile compounds by means of gas chromatography coupled with mass detection. The compounds included aldehydes and methyl-aldehydes, alcohols (primary, secondary and branched chain), ketones, methyl-ketones and esters in winter (WC) and summer (SC) cow’s cheeses, winter (WSh) and summer (SSh) sheep’s cheeses and in winter (WG) and summer (SG) goat’s cheeses. The CB method allows differences to be found as a function of the elaboration of the cheeses, the seasonality of the milk, and the separation of the six groups of cheeses, characterizing the specific volatile chemical compounds responsible for such differences.

The content of free fatty acids in relation to electronic nose sensors responses and sensory evaluation of cheese in a lamb skin sack (Sir iz mišine) throughout ripening

The leading biochemical process during ripening of cheese in a lamb skin sack is lipolysis. In order to evaluate the influence of free fatty acids (FFA) liberated during lipolysis, on the cheese in a sack flavour and aroma, the relationship between sensory properties (odour, taste and total sensory score) and FFA content throughout ripening was determined. Additionally, differentiation of cheeses in various ripening stages was performed by analysis of specific profile of cheese volatile compounds using electronic nose. The obtained results demonstrated that the content of certain FFA is responsible for specific flavour and aroma in various ripening stages, which directly influence the consumers’ sensory scores of the cheese. The concentration of fatty acids C 14:0, C 14:1, C 17:0, C 18:0, C 18:2n-6 and C 23:0 (P&lt;0.05), as well as C 16:0, C 18:3n-3, C 23:0 (P&lt;0.01) in 45 days matured cheese resulted in significantly positive correlation with cheese odour. Concentrations of fatty acids C 8:0, C 17:0, C 18:0 C 18:1n-9t, C 18:1n-9c (P&lt;0.05), C 14:0, C 16:0, C 16:1, C 18:3n-3, C 21:0, C 23:0 (P&lt;0.01), C 12:0, and C 22:0 (P&lt;0.001) correlated significantly with the cheese taste. As a consequence of the ripening time and the ripening conditions, C 4:0, C 6:0 and C 8:0 fatty acids were accumulated and contributed to the lower sensory scores of the 60 days matured cheese. Long-chain unsaturated FFAs ttC 18:2, C 20:2 and C 22:6n-3, also negatively correlated with the sensory properties of cheese in a sack, probably as precursors for synthesis of shorter acids and alcohols. Electronic nose analysis showed very well differentiation of cheeses in various ripening stages and these results are mostly in accordance with the results of consumers’ sensory assessment and physicochemical analyses. Well matured cheese was not well accepted by consumers due to the extensive lipolysis reactions in cheese during ripening. In terms of sensory quality electronic nose could be of a great help to cheesemakers in satisfying consumers requirements for optimal flavour and aroma properties of cheese by estimating ending of ripening time and lipolysis reactions.

Volatile profile of Conciato Romano cheese, a traditional Italian cheese, during ripening

The aim of this paper was to characterize the complete volatile profile of Conciato Romano cheese, a traditional Italian product aged in a mixture of olive oil, wine, and spices, and its modification during ripening, by using SPME sampling and GC/MS analysis of volatiles and considering the rind and body parts separately. Seventy‐six volatile compounds were identified, belonging to chemical classes of acids (8), aldehydes (3), alcohols (14), esters (36), ketones (9), hydrocarbons (1), and terpenes (5). Acids and esters represented the most important chemical classes and are originated from lipolysis and hydrolysis of triglycerides. Aging caused dramatic changes in volatile compounds, particularly on the cheese rind, where the amount of esters, acids, alcohols, and ketones was found particularly abundant at 8 months of aging. Interesting differences were found in volatile headspace composition depending on the external or inner parts. The higher complexity in volatile profile of aged cheese was attributed both to the aging process and tanning mixture. Sensory analysis resulted in higher perception of “sweet” and “stickiness” and significantly lower olfactory persistence in fresh product, while higher values for “salty,” “spicy,” and “persistent” were found in aged ones.Practical applications: The results of our research can be useful to deepen knowledge of cheese volatile compounds and for a better understanding of the interactions between cheese aging and the use of a particular tanning mixture (olive oil, red wine, and spices), used in the Conciato Romano cheese. It can be used for a chemical characterization of the peculiarity found from sensory assessment of this cheese, as well as for control organisms, if further research would confirm the presence of volatile compounds as molecular markers. Finally, industry can take advantage of our research for possible future certifications of Conciato Romano as a Protected Designation of Origin.Conciato Romano, a typical and traditional Italian cheese, was studied to report its complete volatile profile by using the SPME‐GC‐MS technique. The volatile compounds were studied both in fresh and in 6‐ and 8 months‐aged cheese, by separately analyzing the rind and body of the product.

Polymeric ionic liquid coatings versus commercial solid-phase microextraction coatings for the determination of volatile compounds in cheeses

The extraction performance of four polymeric ionic liquid (PIL)-based solid-phase microextraction (SPME) coatings has been studied and compared to that of commercial SPME coatings for the extraction of 16 volatile compounds in cheeses. The analytes include 2 free fatty acids, 2 aldehydes, 2 ketones and 10 phenols and were determined by headspace (HS)-SPME coupled to gas chromatography (GC) with flame-ionization detection (FID). The PIL-based coatings produced by UV co-polymerization were more efficient than PIL-based coatings produced by thermal AIBN polymerization. Partition coefficients of analytes between the sample and the coating (Kfs) were estimated for all PIL-based coatings and the commercial SPME fiber showing the best performance among the commercial fibers tested: carboxen-polydimethylsyloxane (CAR-PDMS). For the PIL-based fibers, the highest K(fs) value (1.96 ± 0.03) was obtained for eugenol. The normalized calibration slope, which takes into account the SPME coating thickness, was also used as a simpler approximate tool to compare the nature of the coating within the determinations, with results entirely comparable to those obtained with estimated K(fs) values. The PIL-based materials obtained by UV co-polymerization containing the 1-vinyl-3-hexylimidazolium chloride IL monomer and 1,12-di(3-vinylimiazolium)dodecane dibromide IL crosslinker exhibited the best performance in the extraction of the select analytes from cheeses. Despite a coating thickness of only 7 µm, this copolymeric sorbent coating was capable of quantitating analytes in HS-SPME in a 30 to 2000 µg L(-1) concentration range, with correlation coefficient (R) values higher than 0.9938, inter-day precision values (as relative standard deviation in %) varying from 6.1 to 20%, and detection limits down to 1.6 µg L(-1).

Potential of near infrared spectroscopy for the analysis of volatile components in cheeses

Near Infrared Spectroscopy (NIRS) was used for the determination of volatile compounds in cheeses allowed to ripen for different times using a remote fibre-optic reflectance probe. To do so, cheeses with known and varying percentages of cow's, ewe's, and goat's milk were elaborated and used as reference material. The volatile compounds determined were: acetaldehyde, ethanol, 1-propanol, 2-butanol, 2-pentanol, 3-methyl-1-butanol, 2-butanone, 2-pentanone, 2-heptanone and 2-nonanone. The regression method employed was the modified partial least squares (MPLS). The calibration results using 67–72 samples of cheese had a correlation coefficients (RSQ) between 0.600 for the 3-methyl-1-butanol and 0.903 for the 2-nonanone. The robustness of the method was confirmed by applying it to twenty new samples of different compositions and ripening times which did not belong to the calibration group. Likewise, the correlations between the factors of influence studied and the volatile compounds were carried out. The results of the NIRS method are comparable with those of the purge-and-trap-gas chromatography-mass spectrometry.

The development of free amino acids and volatile compounds in cheese ‘Oloumoucké tvarůžky’ (PGI) during ripening

SummaryTwenty‐two free amino acid (FAA) concentrations were observed during manufacture (7 days) and ripening period (42 days follow‐up) of Olomoucké tvarůžky (PGI, smear acid cheese). During the ripening period, the amounts of volatile compounds and selected sensory attributes were also analysed. The free amino acids were determined by means of ion‐exchange chromatography, and the volatile compounds were detected and identified using HS‐SPME coupled with GC/MS method. The development of the individual FAA content positively correlated with the ripening period (r = 0.7734–0.9229; P &lt; 0.01). Forty‐six volatile compounds (14 alcohols; 10 esters; 7 ketones; 5 acids; 4 aldehydes; 3 sulphur compounds; 2 phenol compounds; and 1 terpene) were identified. Concentrations of several compounds increased (e.g. 3‐methylbutanal, 2‐butanol, 2‐butanone; P &lt; 0.05) or decreased (e.g. dimethyldisulphide, methanethiol, 2‐phenylethylacetate, methylbutyric acid; P &lt; 0.05) over cheese ageing. The results gave information about the development of sensory active substances and its precursors in Olomoucké tvarůžky during ripening. In conclusion, we found that free amino acid concentrations and sulphur compounds are positive with improved flavour.

Does milk treatment before cheesemaking affect microbial and chemical traits of ripened cheese? Grana Trentino as a case study

The aim of this study was to evaluate the influence of different storage temperatures and delivery system of the milk on the microbiological and physicochemical characteristics of Grana Trentino, a long-ripened hard-cooked Italian cheese. In particular, 3 kinds of milk storage and delivery were studied: milk delivered to the dairy in the traditional manner without temperature control, milk delivered at 18°C, and milk stored at the farm and delivered at 12°C. Milk, natural whey starter, and cheeses after 18mo of ripening were sampled for microbiological profiles, physicochemical analysis, and proteolysis evaluation, and a study of cheese volatile compounds through a solid-phase microextraction gas chromatography-mass spectrometry technique was performed. Milk microbiota was not affected by any of the treatments. At the end of ripening, free fatty acid and ester contents were significantly higher in cheeses from milk without temperature control. This was probably due to the milk delivery to the dairy in churns causing the fat globule membrane break during transport and, consequently, a greater release of fat and deeper lipolysis. Milk refrigeration at 12°C for 12h before delivery affected the distribution of nitrogen fractions in cheeses. Lower temperatures of milk storage favored a larger soluble nitrogen fraction and greater cheese proteolysis, probably caused by an enhanced plasmin activity. From this work, it is concluded that both milk temperature storage and transport system could affect cheese ripening, leading to significant differences in chemical compounds: if milk was delivered by churns, higher free fatty acid and ester content in cheeses was observed; if milk was stored at 12°C for 12h before delivery, greater cheese proteolysis was induced with consequent faster ripening.

Effect of package type on the composition and volatile compounds of Feta cheese

Feta cheese was manufactured by using artisanal rennet from kids and lambs abomasa and allowed to ripen and store either in tin vessels or wooden barrels. In this study the effect of package type on composition, proteolysis, lipolysis and volatile compounds of cheeses was investigated. Feta cheese ripened and stored in wooden barrels had lower moisture contents than Feta cheese stored in tins. Also Feta in barrels had higher fat and lower salt contents than Feta cheeses stored in tins at 60days of storage, while at 180days the fat and salt contents were almost the same for all cheeses. Proteolysis and lipolysis (total free fatty acids) were similar in the cheeses and were not affected by the package type. The most abundant volatile compounds in all cheeses were the free fatty acids and especially acetic, butanoic, hexanoic, octanoic and decanoic acids. Other major compounds were ethanol and 3-methylbutanol. Feta cheese ripened and stored in wooden barrels had higher levels of acetone, butan-2-one, ethyl esters especially ethylacetate, ethylbutanoate, ethylhexanoate, ethyllactate, ethyloctanoate and ethyldecanoate, phenylethylacetate, 3-methylbutylacetate, 2-phenylethylacetate, as well as butan-1-ol, heptan-2-ol, phenylethanol and decanoic acid than Feta cheese ripened in tin vessels, during storage.