Cheese production is associated with the analysis of its nutritional composition as well as with the sensory evaluation of the acceptance of the products. The paper is aimed at the determination of basic chemical parameters such as the content of proteins, fat, dry matter, salt and, pH and also on the evaluation of sensory properties of hard cheeses by the sensory panel. The GC-MS analysis of cheeses, cheese spreads, and traditional butter was performed to evaluate the aroma profile of the dairy products analyzed. The dry matter in the analyzed cheeses varied between 56.75 and 71.83%, the fat content varied from 18.73 to 30.83%, and the salt from 1.21 to 2.61%. The presence of proteins was found between 27.76 and 32.61% and the pH of the cheeses ranged from 5.21 to 6.01. The results of the sensory analysis were processed using a PCA map. The results showed that sample no. 5 was rated within all attributes as the best. Sample 3, 2, and 1 followed. Sample 4 received the lowest score. The volatile aromatic compounds that contribute to a taste perception were analyzed by GC-MS in dairy products. The aroma profile was built by the volatile compounds that belonged to chemical families of alcohols, aldehydes, ketones, esters, amides, amines, imines, and terpenes. In particular, cheeses contained mostly alcohols (3-methyl-1-butanol), aldehydes (3-methylbutanal and benzaldehyde), and ketones (acetoin, 2,3,3-trimethylcyclobutanone, 2-heptanone, 2,3- butanedione, acetone, 2-butanone, 2-nonanone, 2- pentanone). The spreads most often contained alcohols (represented by 2-methyl-1-butanol, 3-methyl-1-butanol and cyclopropane-1,2,3-d3-methanol), aldehydes (2-methylbutanal, 3-methylbutanal, benzaldehyde) and ketones (acetoin, 2-heptanone, 2-pentanone, 2-butanone and 2,3-butanedione).
Milk and dairy products such as cream, butter, yogurt, kefir, and cheese have been consumed around the world for millennia. Milk and other dairy products are indispensable for daily life, and their aroma characters are unique and provide great value in many processed foods, candies, cookies, and others (
The basic nutritional composition of the cheese can be determined by traditional chemical reference methods for measuring fat (e.g. ether extraction), protein content (Kjeldahl), moisture (gravimetric determination by oven drying), and salt (titration with silver nitrate according to Volhard), which are accurate but also too slow and impractical for rapid analyzing of large numbers of cheese samples in laboratories. At present, fast process and more cost-effective methods are used, such as near-infrared spectrometry (NIR), mid-infrared spectroscopy (MIR), or near-infrared transmittance spectroscopy (NIT) for the simultaneous determination of multiple chemical parameters (fat, protein, salt, and moisture) (
Aroma profile and volatile compounds analysis in food is possible by various olfactometry methods such as Charm analysis, AEDA (aroma extract dilution analysis), odour unit, and other methods (
Dairy products and their aroma profile and flavour have been intensively studied.
The paper aims to evaluate selected chemical and physical parameters and sensory properties of cheeses and characterization of the aroma profile of cheeses, cheese spreads, and traditional butter of Slovak origin.
Cheeses were studied to evaluate the consistency of chemical composition, acceptability of cheeses by a sensory panel. An exploration of cheeses, cheese spreads, and traditional butter by GC-MS was performed to confirm the differences in the aroma profile.
Cheeses and cheese spreads and butter were obtained from cheese producer Dubník, the Slovak Republic in three different batches. Samples of five types of hard cheese differ in flavouring spices and length of ripening. Hard cheeses were analyzed for basic physical and chemical composition by NIR and sensory panel. 11 samples of dairy products (including above mentioned 5 types of hard cheese, 5 types of cheese spreads, and one type of traditional butter) differed in the technological process of their production ). All 11 samples were analyzed by GC-MS for aroma profile determination. The hard cheese samples were analyzed by NIR and sensory panel.
All analyzed samples are characterized as follows: no. 1 – hard cheese with chili flakes „Ľahké pierko s čili“; no. 2 – 6 months rippening hard cheese „Kryštálová Kamenica“; no. 3 – 3 months rippening hard cheese „Sýta Rubaň“; no. 4 – hard cheese with chives „Jemný Dubník pažítka“; no. 5 – hard cheese with 4 spices „Ľahké pierko 4 korenia“; no. 6 – cheese spread with smoked cheese „Syrová nátierka s údeným syrom“; no. 7 – cheese spread with onion „Syrová nátierka sladká cibuľka“; no. 8 – cheese spread with hot paprika „Syrová nátierka pálivá paprika“; no. 9 – cheese spread with sweet paprika „Syrová nátierka dolniacka paprika“; no. 10 – cheese spread with emmental cheese „Syrová nátierka Ementálček“; no. 11 – traditional butter „Tradičné maslo“.
The analyses did not require special chemicals. We used deionized water and ethanol (96%, p.a., nondenatured, Centralchem Ltd., Slovakia) for washing the equipment.
No animal and biological material was used.
NIR spectrometer, type MPA (Bruker Optik GmbH, USA) was applied for the determination of the basic chemical composition of cheeses. Selected chemical parameters (dry matter, fat, salt, pH, proteins) were measured at the AgroBioTech SPU research center. The cheese samples were homogenized into a fine powder, then transferred to a Petri´s dish (type Duraplan) and placed in the apparatus. The NIR instrument was calibrated by O.K. SERVIS BioPro, Ltd. for hard cheeses in the range as follows: fat (5 – 43.6%), NaCl (0.04 – 2.85%), proteins (13.6 – 37.10%), dry matter (24.2 – 72.6%) and pH (4.93 – 6.35).
The aroma profile was analyzed by gas chromatography coupled to mass spectrometry (GC-MS). Agilent 7890B gas chromatograph coupled with an Agilent 5977A mass spectrometer (Agilent Technologies Inc., Palo Alto, CA, USA) was used. Separation was performed by a DBWAXms column (30 m × 0.32 mm × 0.25 μm; Agilent Technologies) working with the temperature program and MS conditions according to
The samples were used after cutting/homogenization into appropriate size and by adjusting the temperature (for NIR and sensory panel analysis).
NIR analysis required homogenization of the cheese samples and then the samples were put into glass Petri´s dishes (type Duraplan) in amount 20 g.
For GC-MS analysis, the cheese samples were cut into small pieces. 4 g of each sample (cheese, spread, or butter) was weighed into clean 20 mL headspace vials covered by a magnetic cap with a septum. The samples prepared were stirred at 50 °C or 15 minutes on a shaker included as a part of the GC headspace autosampler (Combi Pal, Alpha M.O.S.).
Sensory analysis was performed in the sensory laboratory. The equipment of the sensory laboratory and the course of the evaluation were performed based on the
Statistical analysis was performed in the program Excel with XLSTAT (vs. 2020.3.1) statistical software for Excel. Chemical parameters were analyzed with descriptive statistics (means, standard deviations, minimum, maximum values) and results were visualized in boxplots. Data from the sensory panel were tested for normality with the Shapiro-Wilk test on a significance level
The results obtained can be divided into three parts – chemical composition, sensory evaluation, and aroma profile.
The chemical composition results are summarized in Table
Chemical composition of cheese samples.
Sample | Dry matter (%) | Fat (%) | NaCl (%) | pH | Proteins (%) | ||||||
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1 | Ľahké pierko s čili | 60.65 | 0.42 | 20.56 | 0.21 | 1.72 | 0.07 | 5.61 | 0.02 | 31.75 | 0.01 |
2 | Kryštálová Kamenica | 65.98 | 0.05 | 25.06 | 0.67 | 1.90 | 0.11 | 5.86 | 0.02 | 32.61 | 0.18 |
3 | Sýta Rúbaň | 71.83 | 3.43 | 30.83 | 0.05 | 2.61 | 0.51 | 6.01 | 0.02 | 31.22 | 0.06 |
4 | Jemný Dubník pažítka | 62.66 | 0.80 | 29.02 | 0.40 | 1.45 | 0.04 | 5.50 | 0.06 | 27.76 | 0.36 |
5 | Ľahké pierko 4 korenia | 56.75 | 2.75 | 18.73 | 1.31 | 1.21 | 0.01 | 5.21 | 0.17 | 30.15 | 0.09 |
Note:
Boxplots of chemical composition variability. Note:
The fat content ranged from 17.42 to 30.88% and the salt from 1.2 to 2.1%. Proteins accounted for 27.4 to 32.43%. The acidity of the cheeses, characterized by a pH value, was in the range of 5.04 to 6.03. The highest values in the most of parameters were determined in Sýta Rúbaň cheese, except for the protein content.
The lowest values of these parameters were found in cheese with 4 types of spices, again except for protein content. A visual expression of the consistency of the individual cheese chemical composition data is shown in Figure
Different types of cheese were analyzed in literature to evaluate basic chemical composition. Ricotta cheeses were analyzed by
Kuflu cheese, a Turkish mould-ripened variety was studied by
Sensory analysis was performed in the sensory laboratory. Trained sensory panels are important tools for assessing the quality of food and non-food products (
Sensory analysis by the sensory panel. Note: no. 1 – hard cheese with chili flakes „Ľahké pierko s čili“; no. 2 – 6 months rippening hard cheese „Kryštálová Kamenica“; no. 3 – 3 months rippening hard cheese „Sýta Rubaň“; no. 4 – hard cheese with chives „Jemný Dubník pažítka“; no. 5 – hard cheese with 4 spices „Ľahké pierko 4 korenia“.
This type of graph allows a better interpretation of the share of individual characteristics in the main components. A PCA biplot shows both PC scores of samples (dots) and loadings of variables (vectors). The further away these vectors are from a PC origin, the more influence they have on that PC.
In our biplot, the most important variables in the sensory evaluation were overall acceptability and appearance, almost no influence had consistency and aroma odour. The results of the sensory analysis (Figure
The GC-MS method is often used to characterize the aromatic profile of dairy products. We have found the presence of the following aromatic compounds. The volatile compounds that were identified belong to several chemical groups: alcohols, aldehydes, ketones, carboxylic acids, esters, amides, amines, imines, and terpenes (Table
Cheese aroma profile.
No. | Compound | Percentage area | Aroma | |
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1. | acetic acid | 20.82 | 1.86 | sour fruity |
butanoic acid | 5.41 | 0.74 | unpleasant | |
2,3,3-trimethyl-cyclobutanone | 1.99 | 1.27 | unknown | |
5-methyl-2-heptene | 1.64 | 0.46 | nutty | |
2-heptanone | 0.76 | 0.20 | cheesy | |
hexanoic acid | 2.85 | 0.40 | fatty | |
2 | 2,3-butanedione | 12.68 | 3.16 | buttery |
3-methyl-butanal | 3.94 | 1.67 | aldehydic | |
acetoin | 26.3 | 3.48 | buttery | |
3-methyl-1-butanol | 9.79 | 2.13 | fermented | |
butyl-isocyanatoacetate | 3.76 | 0.26 | sulfuric | |
3 | (2-aziridinylethyl)amine | 16.46 | 6.58 | unknown |
acetic acid | 22.28 | 2.09 | sour fruity | |
2-fluoro-acetamide | 2.35 | 1.17 | unknown | |
acetoin | 20.52 | 17.50 | buttery | |
butanoic acid | 1.30 | 0.20 | cheesy | |
2,4-dimethyl-hexane | 0.58 | 0.12 | unknown | |
(E)-4-octene | 1.28 | 0.21 | unknown | |
2-heptanone | 0.65 | 0.14 | cheesy | |
4 | acetone | 11.15 | 1.84 | fruity |
2-butanone | 13.53 | 8.02 | ethereal | |
malonic acid | 0.76 | 0.04 | odourless | |
malonic acid | 1.11 | 0.65 | odourless | |
2-pentanone | 4.44 | 0.14 | fruity | |
3-methyl-1-butanol | 0.45 | 0.21 | fermented | |
butanoic acid | 17.38 | 1.84 | cheesy | |
(E)-4-octene | 0.84 | 0.19 | unknown | |
2-heptanone | 8.78 | 2.19 | cheesy | |
benzaldehyde | 0.66 | 0.25 | almond | |
hexanoic acid | 8.45 | 0.38 | fatty | |
2-nonanone | 3.42 | 0.84 | fruity | |
5 | (2-aziridinylethyl)amine | 14.36 | 1.94 | unknown |
2,3-butanedione | 18.73 | 6.34 | buttery | |
acetoin | 15.28 | 2.9 | buttery | |
3-methyl-1-butanol | 1.59 | 0.24 | fermented | |
butanoic acid | 0.26 | 0.02 | cheesy | |
3-methyl-butanoic acid | 1.23 | 0.21 | sour fruity | |
β-phellandrene | 1.86 | 0.29 | minty | |
4-methylene-1-(1-methylethyl)-bicyclo[3.1.0]hexane | 1.37 | 0.28 | woody | |
β-myrcene | 0.61 | 0.05 | spicy | |
α-phellandrene | 6.16 | 0.62 | terpenic | |
o-cymene | 2.01 | 0.27 | unknown | |
D-limonene | 13.59 | 0.88 | citrusy | |
caryophyllene | 4.15 | 0.23 | spicy |
Note: no. 1 – hard cheese with chili flakes „Ľahké pierko s čili“; no. 2 – 6 months rippening hard cheese „Kryštálová Kamenica“; no. 3 – 3 months rippening hard cheese „Sýta Rubaň“; no. 4 – hard cheese with chives „Jemný Dubník pažítka“; no. 5 – hard cheese with 4 spices „Ľahké pierko 4 korenia“.
Cheese spreads and butter aroma profile.
No. | Compound | Percentage area | Aroma | |
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6 | butyl(formyl)formamide | 3.33 | 2.21 | fruity |
2,3-butanedione | 1.53 | 0.6 | buttery | |
2-butanone | 2.57 | 1.75 | ethereal | |
3-methyl-butanal | 1.27 | 0.44 | aldehydic | |
2-methyl-butanal | 0.68 | 0.37 | chocolate | |
2-pentanone | 3.15 | 1.42 | fruity | |
acetoin | 20.4 | 6.25 | buttery | |
2-heptanone | 6.98 | 2.06 | cheesy | |
benzaldehyde | 0.81 | 0.23 | almond | |
hexanoic acid | 1.72 | 0.96 | fatty | |
7 | 2,3-butanedione | 5.56 | 1.55 | buttery |
3-methyl-butanal | 1.02 | 0.49 | aldehydic | |
acetoin | 10.35 | 0.2 | buttery | |
butanoic acid | 19.75 | 1.47 | cheesy | |
ethyl butanoate | 2.01 | 0.24 | fruity | |
hexanoic acid | 33.65 | 5.57 | fatty | |
ethyl hexanoate | 3.07 | 0.21 | fruity | |
octanoic acid | 3.93 | 0.79 | fatty | |
8 | butyl(formyl)formamide | 0.85 | 0.83 | fruity |
nitroso-methane | 4.64 | 2.3 | unknown | |
acetic acid | 4.28 | 0.87 | sour fruity | |
acetoin | 12.46 | 1.84 | buttery | |
butanoic acid | 17.77 | 1.96 | cheesy | |
ethyl butanoate | 2.06 | 0.12 | fruity | |
methoxy-phenyl-oxime | 0.85 | 0.13 | unknown | |
hexanoic acid | 34.65 | 2.24 | fatty | |
ethyl hexanoate | 2.93 | 0.58 | fruity | |
octanoic acid | 4.75 | 0.32 | fatty | |
9 | 2-acetonyl-3-cyano-2.3-dimethyl cyclobutane-1-carboxylic acid | 2.2 | 2.07 | unknown |
dimethylamine | 3.09 | 0.42 | unknown | |
2,3-butanedione | 0.83 | 0.45 | buttery | |
2-butanone | 2.25 | 1.69 | ethereal | |
3-methyl-butanal | 1.03 | 0.14 | aldehydic | |
2-methyl-butanal | 1.03 | 0.66 | chocolate | |
2-pentanone | 11.53 | 1.89 | fruity | |
acetoin | 13.28 | 1.56 | buttery | |
2-methyl-1-butanol | 1.30 | 0.99 | roasted | |
ethyl butanoate | 1.08 | 0.32 | fruity | |
2-heptanone | 7.59 | 1.69 | cheesy | |
methoxy-phenyl-oxime | 3.50 | 0.92 | unknown | |
hexanoic acid | 1.99 | 0.92 | fatty | |
10 | cyclopropane-1,2,3-d3-methanol | 8.96 | 2.29 | unknown |
acetic acid | 8.86 | 0.63 | sour fruity | |
3-methyl-butanal | 1.39 | 0.31 | aldehydic | |
2-methyl-butanal | 1.76 | 0.2 | chocolate | |
propanoic acid | 21.57 | 1.87 | soury | |
acetoin | 15.60 | 0.39 | buttery | |
3-methyl-1-butanol | 0.65 | 0.12 | fermented | |
2-methyl-1 butanol | 1.79 | 0.5 | roasted | |
ethyl butanoate | 0.67 | 0.2 | fruity | |
2-heptanone | 3.63 | 0.74 | cheeesy | |
methoxy-phenyl-oxime | 1.92 | 0.68 | unknown | |
ethyl hexanoate | 0.9 | 0.2 | fruity | |
11 | methoxy-phenyl-oxime | 5.72 | 2.86 | unknown |
benzaldehyde | 5.96 | 3.78 | almond | |
benzyl alcohol | 7.92 | 9.07 | flowery |
Note: no. 6 – cheese spread with smoked cheese „Syrová nátierka s údeným syrom“; no. 7 – cheese spread with onion „Syrová nátierka sladká cibuľka“; no. 8 – cheese spread with hot paprika „Syrová nátierka pálivá paprika“; no. 9 – cheese spread with sweet paprika „Syrová nátierka dolniacka paprika“; no. 10 – cheese spread with emmental cheese „Syrová nátierka Ementálček“; no. 11 – traditional butter „Tradičné maslo“.
Heat map.
Aldehydes (specifically 3-methylbutanal and benzaldehyde) were an important group of volatile compounds in cheeses with a presence in several samples. Due to their low odour detection thresholds, these compounds contribute significantly to the aroma features of the cheeses. Among the carbonyl compounds, ketones were also represented, namely acetoin, 2,3,3-trimethylcyclobutanone, 2-heptanone, 2,3-butanedione, acetone, 2- butanone, 2-nonanone, 2-pentanone. Alcohols also have a low odour detection threshold, which gives dairy products herbal, woody and fatty tones. We identified alcohols represented by 3-methyl-1-butanol in our cheese samples. Terpenes (specifically β-phellandrene, α-phellandrene, β- myrcene, o-cymene, D-limonene, and caryophyllene) were also identified in sample 5 (cheese “Ľahké pierko 4 korenia”) to confirm the spicy aroma of the sample. Carboxylic acids such as acetic acid, butanoic acid, caproic acid (hexanoic acid), heptanoic acid, malonic acid, and 3- methyl-butanoic acid were present in the cheese samples.
Sample 1 with chive flavour had the largest proportion of acetic and butyric acid. In sample 2 with chili flavour, acetoin was present in the highest concentrations, followed by 3-methyl-1-butanol, 2,3-butanedione. Sample 3 was characterized by the highest proportion of acetoin and acetic acid, followed by (2-aziridinylethyl)amine. In sample 4 (Kamenica matured Parmesan-style cheese) the most abundant was butanoic acid, followed by acetone.
In the last sample were dominant 2,3-butanedione, (2- aziridinylethyl) amine, acetoin, D-limonene, followed by terpenes such as α-phellandrene, caryophyllene, o-cymene, β-phellandrene, which originated from the addition of spices.
Cheddar cheeses were analyzed on aroma profile by GCMS by the authors
The most abundant compounds were ketones (especially 2-heptanone and 2-pentanone), then 2-propanone, 2- nonanone, 2-butanone, 1-pentanol, 2-ethyl-1-hexanol, furfural, and 2-furan methanol.
Our results corresponded more closely with analyzes of the Cheddar cheeses, which belong to ripening cheeses, and therefore we also found these compounds in our samples of ripening cheeses. The similarities in dominant compounds were also found with non-cooked semi-hard cheeses.
Processed cheese is an attractive product that enjoys great popularity. The basic raw material for processed cheese and spreads are natural cheeses and other dairy materials and non-dairy raw materials, as well as emulsifying salts (
These components contribute to the aroma of the products. The aroma profile of the cheese spreads in our study was characterized by the following aromatic compounds.
Oxygen derivatives of hydrocarbons such as alcohols (represented by 2-methyl-1-butanol, 3-methyl-1-butanol, and cyclopropane-1,2,3-d3-methanol), aldehydes (2- methylbutanal, 3-methylbutanal, benzaldehyde) occurred ), ketones (acetoin, 2-heptanone, 2-pentanone, 2-butanone, and 2,3-butanedione), carboxylic acids (propanoic acid, butanoic acid, hexanoic acid, octanoic acid, acetic acid, 2- acetonyl-3-cyano-2,3-dimethylcyclobutane-1-carboxylic acid) and esters (ethyl butanoate and ethyl hexanoate), the nitrogen derivatives were amines (dimethylamine) and oximes (methoxyphenyloxime) and amides (butyl(formyl) formamide).
Acetoin was dominant in sample 6 with the addition of smoked cheese, followed by 2-heptanone, butyl (formyl) formamide, 2-pentanone. Sample 7 with onion flavour had the largest proportion of hexanoic acid, butanoic acid, and acetoin.
Sample 8 was spicy with the addition of hot peppers, and hexanoic acid, butanoic acid, and acetoin were the most abundant. Acetoin and 2-pentanone had the largest proportion in sample 9. And in the last Emmental-flavoured sample 10, propanoic acid was the most abundant, followed by acetoin, acetic acid, cyclopropane-1,2,3-d3-methanol.
Butter has appreciated sensory attributes such as flavour, aroma, and melting near the body temperature, which results in a pleasant sensation in the mouth (
We assume that an insufficient number of standards have influenced the identification of GC-MS compounds, so a more detailed study of the aroma profile in butter would need to take this into account, and investment in standards for compounds that have the highest probability to occur in butter should be considered.
In this paper, we evaluated selected chemical parameters (protein content, fat, dry matter, salt, and pH) and sensory properties of hard cheeses, and aroma profiles of cheeses, cheese spreads, and butter of Slovak production. In general, the dry matter content was higher for ripening cheeses compared to cheeses with herbs and spices. The same trend was also confirmed for the salt content of the cheeses, where the ripening cheeses had the highest salt contents probably due to the increasing concentration of salt during the ripening process. The fat content did not follow this trend. We observed a lower pH in samples with herbs and ripening cheeses were characterized by a higher pH. The protein content was relatively balanced in all samples except for the samples with the addition of chives. The consistency of the parameters measured was confirmed within the 3-month monitoring. Within the sensory panel, the sensory properties of cheese samples and cheese spreads were evaluated and the sensory acceptability of the samples was evaluated. The highest score obtained cheese with 4 spices, however, all samples were evaluated as acceptable for the consumers.
The application of sophisticated analytical methods in the study of aroma profiles of food is currently very widespread. The implementation of GC-MS and e-nose in the analysis of dairy products in the food industry consists of e.g. in the classification of products in terms of sensory properties, type, geographical origin, ripening stage (in the case of cheeses), or prediction of their durability. GC-MS and e-nos thus become powerful tools for monitoring indicators of food quality and origin. We focused on the use of the GC-MS method to evaluate the presence of volatile substances responsible for the aromatic properties of selected dairy products - cheeses, spreads, and butter of Slovak production. In general, it can be stated that the samples did not show many similarities in terms of the presence and abundance of the analyzed volatile compounds. The identified volatile compounds belonged to several chemical groups, namely oxygen derivatives of hydrocarbons such as alcohols, aldehydes, ketones, carboxylic acids, esters, amides, nitrogen derivatives such as amines, imines. Compounds from the group of terpenes, the origin of which can be attributed to plant ingredients, were also present in the samples of herbs and spices flavoured.
AgroBioTech SPU research center is greatly acknoledged for possibilty of NIR and GC-MS analysis. We would like to thank to Ing. Jana Štefániková, Ph.D., for performance of GC-MS analysis.
This work was supported by the Slovak Research and Development Agency under the Contract no. APVV-17- 0508 and the Contract no. APVV-19-0180.
The authors declare no conflict of interest.
This article does not contain any studies that would require an ethical statement.