Changes in volatile, sensory and microbial profiles during preparation of smoked ewe cheese

BACKGROUND: Oscypek is a special type of Polish smoked ewe cheese with a unique flavour described as slightly sour, piquant, salted and smoked. In this study the volatile, sensory and microbial profiles of Oscypek cheese were analysed during its various preparation stages of curding, scalding, brining and smoking. RESULTS: The smoked ewe cheese was characterised by 54 volatile compounds belonging to nine different chemical groups (free fatty acids, esters, ketones, alcohols, aldehydes, furans/furanones, phenols, sulfur compounds, terpenes). The sensory aroma profile analysis of unsmoked and smoked cheese showed an important correlation with the analysis of volatile compounds. The microbial profile data indicated that in smoked cheese such as Oscypek the levels of selected bacteria diminished after the curding stage as a result of the subsequent scalding, brining and smoking stages. CONCLUSION: From the results it can be concluded that, although the analysed smoked cheese consisted of three groups of compounds, the first derived from biochemical reactions (free fatty acids, esters, ketones, alcohols, aldehydes, sulfur compounds), the second from smoking (furans and furanones, phenols) and the third from milk flavour (terpenes), it is the smoking process that mainly influences its typical flavour. Copyright © 2011 Society of Chemical Industry     

A study of the volatile composition of Minas cheese

Minas cheese is a food product of significant economic importance to the Brazilian dairy industry. With the intent of providing product identity for legal, economic and manufacturing purposes, several studies have been conducted to define the proximate composition, starter and ripening microflora and manufacturing protocol for Minas cheese. However, studies have yet to characterize the flavor character of Minas cheese, namely the volatile profile. For this purpose, volatiles were investigated using dynamic headspace sampling and GC-MS analysis. Quantitation was based on the recovery of authentic compounds where available. A total of 54 compounds were positively identified and 51 quantified, including fatty acids (11), alcohols (14), aldehydes (5), ketones (6), esters (7), terpenes (8) and lactones (2). The impact of individual volatile compounds on the flavor profile of Minas cheese is discussed. Some of major metabolic pathways for their biosynthesis are reviewed to indicate the possible origin of the compounds identified.     

Comparison of the volatile composition and sensory characteristics of Spanish PDO cheeses manufactured from ewes’ raw milk and animal rennet

Idiazabal, Manchego, Roncal and Zamorano varieties are the Spanish cheeses manufactured under Protected Denomination of Origin (PDO) from ewes’ raw milk and coagulated with animal rennet. Two batches of each cheese variety were ripened for six months and the cheeses were compared for sensory characteristics and composition of volatile compounds. Seventy-six volatile compounds were identified by GC-MS analysis of headspaces of the cheeses. The volatile profile of the four PDO cheeses differed significantly. Acids were the most abundant volatile compounds in Idiazabal, Roncal, and Zamorano cheeses, whereas alcohols were the main volatile compounds in Manchego cheese due to the large percentage of 2-butanol. Aldehydes, ketones and esters were minor compounds in all the cheese varieties, whereas terpenes and unsaturated hydrocarbons were only found in Manchego cheese. The sensory profiles, of the four PDO cheeses also differed significantly. The highest scores for sharp, brine and rennet odours, and rancid and rennet flavours were assessed in Idiazabal and Zamorano cheeses, whereas milky and buttery odour scores were higher in Manchego, Roncal and Zamorano cheeses than in Idiazabal cheese. Principal component analysis was applied to sensory attributes and volatile composition of the cheeses. Differences in flavour and odour attributes were correlated with differences in the volatile compounds. Two principal components correlating sensory attributes and volatile compounds were defined as “strength factor” and “sweetness factor”. The “strength factor” distinguished among the four cheese varieties, except between Roncal and Manchego cheeses, and the “sweetness factor” distinguished the Zamorano cheese from the Idiazabal, Manchego and Roncal cheeses.     

The mozzarella cheese flavour profile: a comparison between judge panel analysis and proton transfer reaction mass spectrometry

Described in this paper is a comparison of results obtained in flavour profiling with two different approaches: classical sensory analysis and a novel instrumental technique. The mozzarella cheese flavour profile of seven different brands has been described by a sensory panel of eight judges. The same brands have been studied by means of proton transfer reaction mass spectrometry (PTR‐MS), a novel technique well suited for detecting volatile organic compounds (VOCs) down to the pptv level in air, without any need for sample concentration or trapping. The PTR mass spectra of the headspace of mozzarella samples held at 36 °C have been compared with the judge panel flavour profile. Multivariate statistical data analysis shows that the two methods perform comparable sample discrimination. Even though several questions are still open (definition of better instrumental parameters, improvements in sampling set‐up, spectral interpretation), the PTR‐MS technique appears to be a very promising method for the instrumental evaluation of the flavour sensory profile of food. This opens up new opportunities both in the control of quality and technological processes as well in the fundamental comprehension of the physiological processes of aroma perception. © 2000 Society of Chemical Industry     

Influence of exopolysaccharide‐producing cultures on the volatile profile and sensory quality of low‐fat Tulum cheese during ripening

The objective of this investigation was to compare the composition and changes in the concentration of volatiles in low‐fat and full‐fat Tulum cheeses during ripening. Tulum cheese was manufactured from low‐ or full‐fat milk using exopolysaccharide (EPS)‐producing or non‐EPS‐producing starter cultures. A total of 82 volatile compounds were identified belonging to the following chemical groups: acids (seven), esters (21), ketones (14), aldehydes (six), alcohols (14) and miscellaneous compounds (20). The relative amounts of acids, alcohols and aldehydes increased in the cheeses made with EPS‐producing cultures during 90 days of ripening. Differences were found in the volatile profile of full‐fat Tulum cheese compared with the low‐fat variant, especially after 90 days of ripening. Exopolysaccharide‐producing cultures changed the volatile profile, and the EPS‐producing cultures including Streptococcus thermophilus + Lactobacillus delbrueckii subsp. bulgaricus + Lactobacillus helveticus (LF‐EPS2) produced cheese with higher levels of methyl ketones and aldehydes than the non‐EPS cultures. In the sensory analysis, full‐fat Tulum cheeses and the cheese produced with the EPS‐producing culture containing Lb. helveticus (LF‐EPS2) were preferred by the expert panel. It was concluded that the use of EPS‐producing starter cultures in the manufacture of low‐fat Tulum cheese had the potential to improve the flavour.     

Cheese flavour development by enzymatic conversions of peptides and amino acids

During ripening of cheese, many biochemical processes take place, which are essential for flavour development. The breakdown of caseins is a prerequisite for flavour development. A good balance between proteolysis and peptidolysis prevents the formation of bitterness in the cheese. For this reason, it is necessary to focus on starter cultures with highly active peptidases, which should be active in the cheese matrix. Amino-acid-converting enzymes (AACEs) are involved in the degradation of amino acids, which are liberated during proteolysis. Their activity results in various volatile (flavour) components; most notably the degradation of methionine results in flavour-active sulphur compounds. AACEs involved in degradation of methionine and other amino acids were identified and their role in (cheese) flavour formation is described. At least two pathways leading to the formation of sulphur compounds were identified. Overproduction of one of the enzymes involved, results specifically in a higher formation of sulphur compounds. This result, together with the observation that flavour production is highly strain-specific amongst various lactococcal bacteria, offers a new potential for industrial applications.     

气相色谱-质谱法中4种不同捕集方式对茶叶香气成分测定的影响

采用固相微萃取(solid phase microextraction,SPME)、吹扫捕集-热脱附(purge & trap-thermal desorption,P&T-TD)、搅拌磁子吸附(stir bar sorptive extraction,SBSE)、动态顶空吸附(head space sorptive extraction,HSSE-1、HSSE-2和HSSE-3)4种捕集方式联用气相色谱-质谱仪对杭州龙井茶、黄山毛峰茶、山东崂山茶和福建乌龙茶进行分析,研究茶的挥发性香气组分。结果显示：茶的香气主要由烯类、醛类、醇类、酮类、酯类、酸类、芳香族化合物、含氮化合物、杂环化合物、含硫化合物、酚类化合物组成;4类茶均含有大量的烯类、醛类、醇类和酮类化合物,其中福建乌龙茶含量最高;杭州龙井茶、黄山毛峰茶和山东崂山茶属绿茶类,酯类、杂环类、芳香族类以及酚类化合物含量相对较高;通过HSSE-1、HSSE-2对茶叶香气成分进行对比,冲泡前后组分种类和含量略有不同。组分之间的差异使茶形成不同产地不同种类的茶叶的特有风味。     

Use of wild Lactobacillus strains in an adjunct culture for a Roncal-type cheese

The effect of an added adjunct culture consisting of facultatively heterofermentative lactobacilli (FHL) on the volatile compounds and sensory characteristics of a Spanish ewes'-milk cheese was examined. Three cheese batches were prepared using a commercial starter, one from raw milk, another from pasteurized milk, and a third from pasteurized milk with an added culture of wild Lactobacillus. paracasei+Lb. plantarum. Analysis of the volatile compounds was carried out by the purge and trap method and gas chromatography with a mass spectrometer and disclosed a total of 86 compounds belonging to the chemical families hydrocarbons, fatty acids, esters, ketones, aldehydes, and alcohols. After ageing for 120 and 240 days, the cheese samples underwent sensory analysis by a panel of expert assessors. The attributes evaluated were characteristic odour and odour intensity and characteristic aroma and aroma intensity. Pasteurization of the milk had an effect on the formation of certain volatile compounds, adversely affecting the characteristic flavour of the cheese. Use of the adjunct culture in addition to the commercial starter improved the flavour of the cheese made from the pasteurized milk, which earned sensory scores similar to those awarded to the cheese made from the raw milk. Use of adjunct cultures consisting of indigenous FHL strains could help to conserve the traditional characteristics of Roncal cheese made from pasteurized milk, although some technical adjustments to the Regulations would be needed.     

A fast and simple method for quantitative determination of fat-derived medium and low-volatile compounds in cheese

Cheese flavour is a mixture of many (volatile) compounds, mostly formed during ripening. The current method was developed to qualify and quantify fat-derived compounds in cheese. Cheese samples were extracted with acetonitrile, which led to a concentrated solution of potential flavour compounds, mainly derived from milk fat. The solution was virtually free from triglycerides, protein and salt from the cheese matrix. Therefore, such an extract could be analysed directly by gas chromatography/mass spectroscopy (GC/MS). In the samples of the three cheese varieties analysed, 61 different compounds were identified, including 23 fatty acids, 14 lactones, 9 esters, 5 ketones, 10 alcohols, and several miscellaneous compounds. Furthermore, most compounds could be quantified by determining their distribution coefficients and thus correcting for their loss during extraction. This method was shown to be suitable for both qualitative and quantitative analysis of medium and low-volatile compounds.     

Improving the quality of Ras cheese made without starter

Trials were carried out to produce Ras cheese of good quality without the use of starter. Cheese was made from cows' milk, pasteurized and acidified with lactic acid or citric acid to pH 5·8; cheese was also made after adding 4·5 g glucono-δ-lactone per kg to the acidified curd. Control cheese was made by the traditional method.The cheese had poor body and texture, weak flavour intensity, and low levels of soluble nitrogen compounds and free volatile fatty acids.Incorporation into the cheese curd of mixtures containing Fromase 100 (fungal protease) and Piccantase B (fungal lipase) or Fromase 100 and Capalase K (animal lipase) enhanced flavour intensity and body characteristics and accelerated the formation of both soluble nitrogen compounds and free volatile fatty acids. The organoleptic properties of the experimental cheese with added enzymes were comparable to the control cheese.     

Comparison of isolation methods for the determination of buckwheat volatile compounds

Five different isolation techniques were combined with gas chromatographic–mass spectrometric determination of aroma compounds from buckwheat: dynamic headspace (DHS) with cryotrapping or sorbent trapping, solid-phase microextraction (SPME), headspace sorptive extraction (HSSE), solvent extraction (SE) and simultaneous distillation–extraction (SDE). Optimisation of each technique is presented, as well as comparison of the chemical profiles obtained by them. Solvent extraction with methanol resulted in the isolation of rather polar and less volatile compounds and was deemed least suitable for the odour-active compounds. Only SPME with DVB/CAR/PDMS fibre was suitable for the isolation of highly volatile compounds in a wider polarity range. DHS extracted the smallest number of compounds, but with the comparable chemical profile as obtained by SDE, which was chosen as the most suitable technique to obtain the aroma compounds of cooked buckwheat. The applied isolation techniques are complementary in their ability to extract a representative aroma profile of buckwheat.     

Quality and ripening changes of Ras cheese made by direct acidification

Trials were carried out to produce Ras cheese of good quality without the use of starter. Cheese was made from pasteurized cow's milk acidified with lactic acid or citric acid to pH 5.8 alone or coupled with mixing the curd with glucono δ lactone (4.5 g/kg curd). Control cheese was made from milk ripened with a starter culture of S. lactis. Resultant cheeses showed poor body and texture, weak flavour intensity and low levels of soluble nitrogen compounds and free volatile fatty acids. Incorporation into the cheese curd of mixtures containing Fromase 100 (fungal protease) and Piccantase B (fungal lipase) or Fromase 100 and Capalase K (animal lipase) enhanced flavour intensity, improved body characteristics and accelerated the formation of both soluble nitrogen compounds and free volatile fatty acids. The organoleptic properties of the experimental cheeses with added enzymes were comparable to those of the control cheese.     

Starter culture development for improving the flavour of Proosdij-type cheese

The use of the additional mesophilic strain B851, which has specific flavour forming abilities, was tested for improving the flavour development of a Proosdij-type cheese made with a combination of an acidifying mesophilic and an adjunct thermophilic culture. This strain was selected because of its ability to produce the branched chain aldehyde, 3-methylbutanal, which is a key flavour compound in Proosdij cheese. In order to control the flavour intensity, the selected strain was first tested at different levels in a defined strain starter culture as well as in combination with a mixed strain starter culture. The results of population dynamics, sensory evaluation and analysis of volatile compounds pointed to the possibility of controlling both the cell numbers of strain B851 as well as the cheese flavour intensity resulting from this strain. Thus, B851 was used to enhance the flavour development of a Proosdij-type cheese made with a new thermophilic culture S1138, developed to prevent crack formation. The addition of culture B851 led to an increase in the overall flavour intensity, indicating that it is possible to tailor the flavour of cheese by using specifically selected cultures, even in combination with complex starter cultures.     

Formation of the aroma of a raw goat milk cheese during maturation analysed by SPME–GC–MS

The volatile profile of the Spanish goat raw milk cheese of the protected designation of origin (PDO) “Queso Ibores” was studied at four stages of maturation (day 1, 30, 60, and 90) by the method of solid-phase micro-extraction–gas chromatography–mass spectrometry (SPME–GC–MS) to determinate the characteristic volatile compounds of this cheese and to know the changes in the volatile profile of this cheese during maturation. According to the PDO, Ibores cheese aroma varies between sweet and mild and it has a strong taste, slightly tart. A total of 64 compounds were detected: 14 acids, 18 alcohols, 13 esters, 6 ketones and 13 compounds which could not be classified in these groups. Carboxylic acids were the most abundant volatile compounds in the headspace of Ibores cheese. Content of volatile compounds was significantly modified (P < 0.05) during ripening. The relative total amounts of acids, esters and ketones increased during the first 60 days of maturation. The most characteristic compounds of Ibores cheese aroma were butanoic, hexanoic and octanoic acids, some alcohols (2-butanol and 2-heptanol), ethyl esters of hexanoic and butanoic acids, some methyl ketones (2-butanone, 2-pentanone and 2-heptanone) and δ-decalactone.     

Aroma–taste interactions between a model cheese aroma and five basic tastes in solution

The flavour perception of cheese results from complex sensory interactions between tastes and aromas. Using a model cheese solution, this study investigated perceived interactions between each of five basic tastes and a cheese aroma mixture containing ten volatile compounds commonly found in cheese. The five tastes – sucrose (sweetness), sodium chloride (NaCl) (saltiness), monosodium glutamate (MSG) (umami), lactic acid (sourness), and caffeine (bitterness) – were individually mixed with cheese aroma in water using a 5 taste level (0.2 log series) by 3 aroma level (0.5 log series) design. Aroma controls with no added taste were also included. This resulted in 18 samples for each single taste–aroma combination. An additional 18 samples were produced using a mixture of all 5 tastes with the 3 aroma levels. A panel of trained assessors (n = 10) evaluated cheese flavour intensity and taste intensity using 100 point line scales. Evaluation was carried out in duplicate, with samples grouped by taste type; 1 evaluation session per taste per replicate. Within type, order of presentation was balanced, and taste type order was randomised between replicates. Cheese flavour intensity was enhanced by sucrose and NaCl, while being suppressed by lactic acid. NaCl enhanced cheese flavour intensity the most at high aroma level, while lactic acid suppressed the most at low aroma level. When MSG level was increased, cheese flavour intensity was enhanced at both low and medium aroma levels, but was suppressed at the high aroma level. The greatest enhancement of cheese flavour intensity was found with the mixture of 5 tastes. Aroma significantly enhanced umami and bitterness, but did not enhance sweetness, saltiness, or sourness. This study showed that the perceived interaction between taste and cheese aroma depended on taste type and on the concentration levels of both taste type and aroma. The mixture of tastes was more effective at enhancing cheese flavour intensity than single tastes. This study provides knowledge that will underpin further study of taste–aroma interactions in a model cheese that aims to optimise cheese flavour intensity and character.     

Oxidative stability of cream cheese stored in thermoformed trays as affected by packaging material,drawing depth and light

The oxidative stability of cream cheese stored in thermoformed trays made of amorphous polyethylene terephtalate (A-PET)/polyethylene (PE), polystyrene (PS)/Ethylene-vinylalcohol copolymer (EVOH)/PE and Polypropylene (PP)/PE with different depth (25, 50 and 70 mm) and colour (black, white and transparent) was studied by sensory evaluation and gas chromatographic analysis of volatile compounds. The polymer combination had an important effect on sensory scores of both sunlight and acidulous flavour in cream cheese stored in the dark for 2, 4 and 6 months. Cream cheese stored in trays made of A-PET/PE had higher acidulous flavour and lower content of hexanal and 2-nonanone. Only small differences were observed between PS/EVOH/PE and PP/PE despite the great diversity of oxygen transmission rates. The drawing depth of the packages had no significant effect on oxidative stability of cream cheese, irrespective of storage in the dark or under illumination. The colour of the examined packaging material had a pronounced effect on photoxidative changes in cream cheese.     

Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurised milk

Cheddar cheeses were made from raw (R1, R8) or pasteurised (P1, P8) milk and ripened at 1°C (P1, R1) or 8°C (P8, R8). Volatile compounds were extracted from 6 month-old cheeses and analysed, identified and quantified by gas chromatography-mass-spectrometry. A detailed sensory analysis of the cheeses was performed after 4 and 6 months of ripening. The R8 cheeses had the highest and P1 the lowest concentrations of most of the volatile compounds quantified (fatty acids, ketones, aldehydes, esters, alcohols, lactones and methional). The R8 and P8 cheeses contained higher levels of most of the volatiles than R1 and P1 cheeses. Ripening temperature and type of milk influenced most of the flavour and aroma attributes. Principal component analysis (PCA) of aroma and flavour attributes showed that P1 and R1 had similar aroma and flavour profiles, while R8 had the highest aroma and flavour intensities, highest acid aroma and sour flavour. The age of cheeses influenced the perception of creamy/milky and pungent aromas. PCA of the texture attributes separated cheeses on the basis of ripening temperature. The R8 and P8 cheeses received significantly higher scores for perceived maturity than P1 and R1 cheeses. The P1 and R1 cheeses had similar values for perceived maturity. In a related study, it was found that concentrations of amino acids and fatty acids were similar in R1 and P1 during most of the ripening period, and R1 and P1 cheeses had low numbers of non-starter lactic acid bacteria (NSLAB). The panel found that ripening temperature, type of milk and age of cheeses did not influence the acceptability of cheese. It is concluded that NSLAB contribute to the formation of volatile compounds and affect the aroma and flavour profiles and the perceived maturity of Cheddar cheese.