The effect of application of cold natural smoke on the ripening of Cheddar cheese

The present study was undertaken to study the effects of application of natural wood smoke on ripening of Cheddar cheese, and to determine the effects of smoking before or after ripening on cheese quality. A 20-kg block of Cheddar cheese obtained immediately after pressing was divided into six approximately 3-kg blocks and ripened at 8 degrees C for up to 270 d. One 3-kg block was taken after 1 d, 1, 3, 6, or 9 mo and smoked for 20 min, then returned to the ripening room for further ripening. Cheeses were sampled at intervals for lactobacilli counts, moisture, pH, and proteolysis. Sensory analysis was conducted on 6 and 9-mo-old cheeses by a trained sensory panel (n = 7). Results show that application of natural wood smoke did not significantly affect cheese pH or primary proteolysis during ripening. However, secondary proteolysis as assessed by the concentrations of free amino acids was generally higher in smoked cheeses than in control cheeses after 6 mo of ripening. Cheese smoked after 6 mo of ripening had better smoked flavor than that smoked after 9 mo of ripening. Cheese smoked after 3 mo of age and further ripened for 6 mo had the highest smoked flavor intensity. It is concluded that it is best to smoke cheese after ripening for at least 3 mo.     

Consumer perception of smoked Cheddar cheese

Consumer perception of smoked cheese was evaluated through focus groups, surveys, and central location testing. Three focus groups (n = 29) were conducted with consumers of smoked cheese. Subsequently, 2 online surveys were conducted. The purpose of the first survey (n = 1,195) was to understand types of smoked cheeses consumed and if consumers associated specific wood smokes with smoked cheese. Next, an adaptive choice-based conjoint (n = 367) was designed to evaluate consumer perception of different attributes of smoked cheese. Maximum difference scaling and familiarity questions were also included in the adaptive choice-based conjoint survey. Following the surveys, a central location test (n = 135) was conducted with cheeses smoked with 3 different woods at a low and high intensity (6 cheeses total). Hierarchical Bayesian estimation, 1-way ANOVA, agglomerative hierarchical clustering, and 2-way ANOVA (smoke type × intensity level) were used to interpret the collected data. Results from the focus groups indicated that smoked cheese was perceived as an artisan, high-end product and that appearance and price were strong purchase factors. In general, consumers were not aware of how smoked flavor was imparted to cheese, but when informed of the processes, they preferred cold-smoked cheese to the addition of liquid smoke flavor. Results from both surveys confirmed focus group observations. Consumers perceived flavor differences among different wood smokes and smoked products. Method of smoking, smoke intensity, type of wood, and type of cheese were the most important attributes for purchase of smoked cheese. When tasting, consumers differentiated smoke aroma and flavor among cheeses and preferred cherry wood smoked cheeses over apple wood or hickory smoked cheeses. Understanding consumer perceptions of smoked cheese will give insight into the desired experience that consumers expect when purchasing smoked cheese.     

Identification of aroma-active compounds in Cheddar cheese imparted by wood smoke

Cheddar cheese is the most popular cheese in the United States, and the demand for specialty categories of cheese, such as smoked cheese, are rising. The objective of this study was to characterize the flavor differences among Cheddar cheeses smoked with hickory, cherry, or apple woods, and to identify important aroma-active compounds contributing to these differences. First, the aroma-active compound profiles of hickory, cherry, and apple wood smokes were analyzed by solid-phase microextraction (SPME) gas chromatography-olfactometry (GCO) and gas chromatography-mass spectrometry (GC-MS). Subsequently, commercial Cheddar cheeses smoked with hickory, cherry, or apple woods, as well as an unsmoked control, were evaluated by a trained sensory panel and by SPME GCO and GC-MS to identify aroma-active compounds. Selected compounds were quantified with external standard curves. Seventy-eight aroma-active compounds were identified in wood smokes. Compounds included phenolics, carbonyls, and furans. The trained panel identified distinct sensory attributes and intensities among the 3 cheeses exposed to different wood smokes (P < 0.05). Hickory smoked cheeses had the highest intensities of flavors associated with characteristic “smokiness” including smoke aroma, overall smoke flavor intensity, and meaty, smoky flavor. Cherry wood smoked cheeses were distinguished by the presence of a fruity flavor. Apple wood smoked cheeses were characterized by the presence of a waxy, green flavor. Ninety-nine aroma-active compounds were identified in smoked cheeses. Phenol, guaiacol, 4-methylguaiacol, and syringol were identified as the most important compounds contributing to characteristic “smokiness.” Benzyl alcohol contributed to the fruity flavor in cherry wood smoked cheeses, and 2-methyl-2-butenal and 2-ethylfuran were responsible for the waxy, green flavor identified in apple wood smoked cheeses. These smoke flavor compounds, in addition to diacetyl and acetoin, were deemed important to the flavor of cheeses in this study. Results from this study identified volatile aroma-active compounds contributing to differences in sensory perception among Cheddar cheeses smoked with different wood sources.     

Components detected by means of solid-phase microextraction and gas chromatography/mass spectrometry in the headspace of artisan fresh goat cheese smoked by traditional methods

The study of the headspace components of fresh smoked goat cheese, was carried out by means of solid-phase microextraction using a polyacrylate fiber followed by gas chromatography/mass spectrometry. The samples studied were six artisan Palmero cheeses manufactured following traditional methods and smoked using pine needles. The cheese regions studied were exterior, interior, and a cross section. In total, more than 320 components were detected, the exterior region being the richest in components, among which were acids, alcohols, esters, hydrocarbons, aldehydes, ketones, furan and pyran derivatives, terpenes and sesquiterpenes, nitrogen derivatives, phenol, guaiacol and syringol derivatives, ethers, and others. In addition to typical cheese components, typical smoke components were also detected; these latter were present especially in the headspace of the exterior region and only those in significant concentrations in the exterior region were also detected in the interior. The main components were acids and phenolic derivatives. These latter compounds play an important role in the flavor of this cheese, and their relative proportions together with the presence of specific smoke components derived from pine leaves may be considered of interest in order to distinguish this cheese from others smoked with different vegetable matter.     

Influence of Water-Soluble Nitrogen and Free Amino Groups on Sensory Attributes of Smoked Mozzarella Cheese

The smoking of cheeses contributes to significant changes in their color, aroma, and also content of free amino groups. The aim of the study was to evaluate changes in sensory attributes of smoked and unsmoked mozzarella cheese during storage for four weeks. It was found that inner layers of both cheeses were equally light despite large differences in their outer layers (ΔL*: 26.33 for smoked and ΔL*: 5.33 for unsmoked). Color of the edge layer in smoked cheese was more saturated than in unsmoked cheese (ΔC* = 17.47). The edge layer in smoked cheese after storage became more saturated (ΔC* = 5.12). Desirability of smoked cheese was 1.5-fold greater than that of unsmoked cheese. Smoking contributed to the disappearance of cooked aroma (by 32%), whey, and cowy/phenolic aromas and intensified the perceptibility of acid taste (8.5 times). Changes were higher in smoked mozzarella because of its higher proteolysis susceptibility.     

Characterisation of aroma‐active compounds,chemical and sensory properties of acid‐coagulated cheese: Circassian cheese

The objectives of this study were to determine basic composition, aroma and sensory characteristics of Circassian cheese. Seven Circassian cheeses were provided by local producers. Aroma compounds were extracted by using solid‐phase microextraction procedure and determined by gas chromatography‐olfactometry system. Water‐soluble, trichloroacetic acid‐soluble and phosphotungstic acid‐soluble nitrogen fractions ranged between 2.30–29.35%, 2.48–9.96% and 3.33–6.26%, respectively. Diacetyl, butyric acid, 2‐acetyl‐1‐pyrroline, 1‐octen‐3‐one and methional were identified at high intensities in cheeses. In addition, ‘cooked’, ‘whey’, ‘creamy’ and ‘fermented’ were defined as characteristic flavour terms for Circassian cheeses.     

Chemical changes that predispose smoked Cheddar cheese to calcium lactate crystallization

We have observed a high incidence of calcium lactate surface crystals on naturally smoked Cheddar cheese in the retail marketplace. The objective of this study was to identify chemical changes that may occur during natural smoking that render Cheddar cheese more susceptible to calcium lactate crystal formation. Nine random-weight (approximately 300 g) retail-packaged samples of smoked Cheddar cheese were obtained from a commercial manufacturer immediately after the samples were smoked for about 6 h at 20°C in a commercial smokehouse. Three similarly sized samples that originated from the same 19.1-kg block of cheese and that were not smoked were also obtained. Within 2 d after smoking, 3 smoked and 3 control (not smoked) samples were sectioned into 5 subsamples at different depths representing 0 to 2, 2 to 4, 4 to 6, 6 to 8, and 8 to 10 mm from the cheese surface. Six additional smoked cheese samples were similarly sectioned at 4 wk and again at 10 wk of storage at 5°C. Sample sections were analyzed for moisture, l(+) and d(−) lactate, pH, and water-soluble calcium. The effects of treatment (smoked, control), depth from cheese surface, and their interactions were analyzed by ANOVA according to a repeated measures design with 2 within-subject variables. Smoked samples contained signficantly lower moisture and lower pH, and higher total lactate-in-moisture (TLIM) and water-soluble calcium-in-moisture (WSCIM) than control cheeses. Smoked samples also contained significant gradients of moisture, pH, TLIM, and WSCIM, with lower moisture and pH, and higher TLIM and WSCIM, occurring at the cheese surface. Gradients of moisture were still present in smoked samples at 4 and 10 wk of storage. In contrast, the pH, TLIM, and WSCIM equilibrated and showed no gradients at 4 and 10 wk. The results indicate that calcium and lactate in the serum phase of the cheese were elevated because of smoking, especially at the cheese surface immediately after smoking treatment, which presumably predisposes the smoked cheeses to increased susceptibility to calcium lactate surface crystallization.     

Occurrence of polycyclic aromatic hydrocarbons in artisanal Palmero cheese smoked with two types of vegetable matter

Palmero cheese is a fresh smoked cheese from the Isle of Palma (Canary Islands), manufactured with goat's milk. To guarantee its safety, the occurrence of polycyclic aromatic hydrocarbons (PAH) in artisanal Palmero cheese smoked with 2 types of vegetable matter (almond shells and dry prickly pear) was studied. The determination of PAH includes extraction and clean-up steps, followed by separation, identification, and quantification of PAH by gas chromatography-mass spectrometry in selected ion-monitoring mode. The most abundant PAH are those with 2 and 3 aromatic rings. Although the highest total PAH concentrations corresponded to the cheeses smoked with almond shells, the degree of PAH contamination of the cheeses studied was lower than that found in other cheeses smoked in the traditional way. The nature of the vegetable material used for smoking seemed to have an influence on the type of PAH formed, especially on alkylderivatives and some light PAH. However, despite the artisanal, and consequently variable, production process of these cheeses, many similarities have been found among their PAH profiles. In fact, relatively constant relationships are observed between the concentrations of certain pairs of PAH. Benzo(a)pyrene was only present in 2 samples, and in much lower concentrations than the maximum allowed legal limits. Therefore, according to the results obtained, it appears that it is possible to obtain a safe product without renouncing the artisanal character or the sensory properties of this type of cheese.     

Occurrence of polycyclic aromatic hydrocarbons in smoked cheese

The presence of polycyclic aromatic hydrocarbons (PAH) in smoked cheeses of different origin was studied. The samples were subjected to an initial extraction of fat and an alkaline treatment, extracted with cyclohexane, cleaned up by means of solid-phase extraction tubes, and analyzed by gas chromatography/mass spectrometry (GC/MS) operating in selective ion-monitoring mode (SIM). The results revealed the presence of numerous polycyclic aromatic hydrocarbons in the exterior zone of the samples, some of them with methyl groups. In all cases, the concentrations of compounds of low molecular weight were much higher than those of high molecular weight. Polycyclic aromatic hydrocarbons with varying degrees of carcinogenicity were identified, including benzo(a)pyrene in concentrations, which, although they did not exceed the limit established for this compound in the rind of ripened cheeses, do exceed the limit of 0.03 microg/kg fixed for other foods smoked with smoke flavorings. Significant differences in the number and concentration of PAH in smoked cheese also were observed from rind to interior, the rind being the most contaminated zone.     

Contamination of cheese by polycyclic aromatic hydrocarbons in traditional smoking. Influence of the position in the smokehouse on the contamination level of smoked cheese

This paper sets out to determine the polycyclic aromatic hydrocarbon (PAH) contamination degree of a traditionally smoked cheese: Herreño cheese, which comes from one of the Canary Islands. Its PAH profile is thoroughly studied by means of gas chromatography-mass spectrometry in SIM mode, and compared with that of an unsmoked cheese. Furthermore, a parameter not previously studied is evaluated, namely the influence of the position of the individual cheeses in the smokehouse on their PAH contamination level. Heavy PAH, among which are included most of the carcinogens, are very scarce and their concentrations low. In fact, benz[a]anthracene, together with chrysene+triphenylene, are the only heavy PAH detected in all of the smoked samples studied. The concentration of benzo[a]pyrene, detected only in 1 of the samples, is below the limit established in Spain for the rind of smoked cheese. In contrast, high concentrations of light PAH have been found, especially of naphthalene and its alkyl derivatives, whose effect on human health is not yet well established. The results derived from the analysis of the PAH profile suggest the potential usefulness of certain ratios between some pairs of PAH (phenanthrene/anthracene, naphthalene/acenaphthylene) to provide information on the PAH contamination source. Furthermore, differences have been found, depending on the position of the cheeses in the smokehouse, those placed in the path followed by the smoke being more contaminated. Therefore, the findings of this study could help in improving the design of smokehouses, to decrease the PAH contamination degree of smoked cheese.     

Proteolysis on Reggianito Argentino cheeses manufactured with natural whey cultures and selected strains of Lactobacillus helveticus

Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter.     

Influence of different smoking techniques on contamination by polycyclic aromatic hydrocarbons in traditional smoked Mozzarella di Bufala Campana

The levels of six polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene and three other PAH were determined in smoked Mozzarella di Bufala Campana. Different smoking techniques were compared to evaluate the risk associated with consumption of these cheeses. Although no maximum limits are set for PAHs in cheese, the levels found in some samples constitute a health risk. In fact, using corrugated cardboard, high levels were detected in the whole product or in the outer part. Also, the use of traditional materials involves the accumulation of PAHs in the outer part, but in the total product concentrations are significantly lower. No contamination was found using liquid smoke.     

Levels of benzo[a]pyrene and benzo[a]anthracene in smoked “Provola” cheese from Calabria (Italy)

Levels of benzo[a]pyrene (BaP) and benzo[a]anthracene (BaA) in “Provola” cheese samples from Calabria, smoked naturally and using commercial smoke-flavouring, have been determined. A comparative study of BaP and BaA concentrations was carried out on rind, exterior zone, core and slice of these samples. Quantitative determination of BaP and BaA was ascertained by HPLC using fluorescence detection. Levels of BaP and BaA were found in all smoked “Provola” cheese samples, but higher in cheese smoked with natural methods (0.46–1.13 µg kg^?1 for BaP and 1.38–9.29 µg kg^?1 for BaA) compared to samples smoked using commercial flavouring (0.085–0.32 µg kg^?1 for BaP and 1.20–2.98 µg kg^?1 for BaA). The smoking process contributes to polycyclic aromatic hydrocarbons contamination; however, for improved food safety, the use of commercial buffered smoke is preferable to traditional smoking procedures.     

N-NITROSOPROLINE AND N-NITROSOSARCOSINE IN ESTONIAN FOODSTUFFS

The N-nitrosoamino acids (NNA) N-nitrosoproline (NPRO) and N-nitrososarcosine (NSAR) are precursors of the carcinogenic N-nitrosamines. Methodology using gas chromatography for their determination and data on their contents in 52 food products are presented. Food products consisted of smoked meats (12), smoked (9) and boiled (11) sausage, cheese (10), fish (7) and beer (3). Results showed that NNA formed during processing, particularly in meat, where levels of NPRO were as high as 353μg/kg. The compounds accumulated in the adipose tissue and surface portion of the product. Smoking caused increased formation of NPRO, while the use of liquid smoke minimized it. NPRO in meat products in natural casings was higher than in synthetic ones, and frying of boiled sausage and hams further enchanced NPRO formation. Like meat, smoked cheese and fish showed consistently higher NNA levels than the non-smoked products. These data indicate means of reducing NNA contents in foods by modification of processing techniques .     

Identification and occurrence of 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid: the main β-carboline alkaloid in smoked foods

Tetrahydro-β-carboline alkaloids are biologically active compounds that occur in foodstuffs. 1,2,3,4-Tetrahydro-β-carboline-3-carboxylic acid, a tetrahydro-β-carboline derived from a Pictet–Spengler condensation reaction among l-tryptophan and formaldehyde, was identified by GC–MS as its N-methoxycarbonyl methyl ester derivative in smoked fish, sausage and cheese. The occurrence of this β-carboline was determined by RP-HPLC-fluorescence in numerous commercially available samples of these products and the concentrations ranges were 0.03–12.2 μg/g, 0.07–6.06 μg/g and 0.01–14.8 μg/g in smoked fish, smoked cheeses and smoked sausages and meats, respectively. These results showed that 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid is the main β-carboline in such products. Smoked foods contained a higher relative amount (2–7 fold) of this compound in their exterior part exposed to the smoke than in their interior counterpart suggesting a reaction involving formaldehyde from smoke and tryptophan. Smoked products appear to be one of the food stuffs with the highest amount of this particular tetrahydro-β-carboline.     

A survey of lipolytic and glycolytic end-products in commercial Cheddar enzyme-modified cheese

The concentrations of L- and D-lactic acid and free fatty acids, C4:0 to C18:3, were quantified in a range of commercial enzyme-modified Cheddar cheeses. Lactic acid in Cheddar enzyme-modified cheeses varied markedly depending on the manufacturer. Differences in the ratio of L- to D-lactic acid indicate that cheeses of different age were used in their manufacture or contained varying levels of nonstarter lactic acid bacteria. The level of lipolysis in enzyme-modified cheese was higher than in natural Cheddar cheese; butyrate was the predominant free fatty acid. The addition of exogenous acetate, lactate, and butyrate was also indicated in some enzyme-modified cheeses and may be used to confer a specific flavor characteristic or reduce the pH of the product. Propionate was also found in some enzyme-modified cheese products and most likely originated from Swiss-type cheese used in their manufacture. Propionate is not normally associated with natural Cheddar cheese flavor; however, it may be important in the flavor and aroma of Cheddar enzyme-modified cheese. Levels of lipolysis and glycolysis appear to highly controlled as interbatch variability was generally low. Overall, the production of enzyme-modified Cheddar cheese involves manipulation of the end-products of glycolysis (lactate, propionate, and acetate) and lipolysis to generate products for specific applications.     

Understanding the role of natural cheese calcium and phosphorous content,residual lactose and salt‐in‐moisture content on block‐type processed cheese functional properties: Cheese hardness and flowability/meltability

Four treatments of natural Cheddar cheese with two levels (high and low) of calcium (Ca) and phosphorus (P), and two levels (high and low) of residual lactose were manufactured. Each treatment was subsequently split prior to the salting step of cheese manufacturing processed and salted at two levels (high and low) for a total of eight treatments. The eight treatments included: high Ca and P, high lactose, high salt‐in‐moisture (S/M) content (HHH); high Ca and P, high lactose, low S/M (HHL); high Ca and P, low lactose, high S/M (HLH); high Ca and P, low lactose, low S/M (HLL); low Ca and P, high lactose, high S/M (LHH); low Ca and P, high lactose, low S/M (LHL); low Ca and P, low lactose, high S/M (LLH); and low Ca and P, low lactose, low S/M (LLL). After 2 months of ripening, each treatment of natural Cheddar cheese was used to manufacture processed cheese using a twin‐screw Blentech processed cheese cooker. All of the processed cheese food formulations were balanced for moisture, fat and salt. Texture and melt‐flow characteristics of the processed cheese were evaluated with different techniques, including texture profile analysis (TPA) for hardness and melt profile analysis. There was a considerable increase in cheese hardness for the processed cheeses prepared from high Ca and P content, and high S/M natural cheeses compared with low Ca and P content and low S/M natural cheeses. Moreover, definite decrease in flow rate and extent of flow was observed for processed cheeses manufactured from high Ca and P content, and high S/M natural cheeses than that of low Ca and P content and low S/M natural cheeses. No considerable trend was observed in hardness and melt‐flow characteristics for the processed cheeses manufactured from high and low residual lactose content natural Cheddar cheeses. This study strongly demonstrates that the characteristics of natural cheese (calcium and phosphorus content, lactose content and salt‐in‐moisture content) used in processed cheese manufacture have a significant impact on processed cheese functionality.     

Determination of bovine lactoferrin concentrations in cheese with specific monoclonal antibodies

In order to determine bovine lactoferrin concentration in cheese, bovine lactoferrin-specific monoclonal antibodies have been raised and an ELISA has been developed to determine lactoferrin concentrations in milk, whey and experimental soft, semi-hard and Swiss-type cheeses made with raw or pasteurised milk. The lactoferrin concentration in cheese was shown to depend on the cheese-making process, with higher values in Swiss-type and semi-hard cheeses than in soft cheeses. Furthermore, Western-blotting analysis of lactoferrin in cheese showed that this protein stayed intact throughout ripening in raw milk cheese, whereas it was partially hydrolysed in cheeses made with pasteurised milk. Based on these observations, we propose that cheese may constitute a natural dairy source of lactoferrin beneficial to health.     

Effect of Penicillium roqueforti and incorporation of whey cheese on volatile profiles and sensory characteristics of mould‐ripened Civil cheese

In this study, four different types of mould‐ripened Civil cheese were manufactured. A defined (nontoxigenic) strain of a Penicillium roqueforti (SC 509) was used as secondary starter for the manufacture of mould‐ripened Civil cheese with and without addition of the whey cheese Lor; in parallel, secondary starter‐free counterparts were manufactured. A total of 83 compounds were identified. Ketones, alcohols and esters were the principal classes of volatile components. Principal component analysis of the headspace volatiles grouped cheeses by age and type. P. roqueforti inoculated cheese was clearly separated from the other cheeses at 180 days of ripening, and these cheeses were characterised with high levels of ketones (e.g., 2‐butanone, 2‐heptanone). Differences in the panel scores between the cheese samples were not significant during the first stage of ripening (up to 60 days); as ripening proceeded, these differences were become evident and P. roqueforti inoculated cheeses received higher scores than others. Addition of Lor in the manufacture of mould‐ripened Civil cheese caused lower points by the sensory panel, and the cheese inoculated with P. roqueforti and Lor‐free was the best type of mould‐ripened Civil cheese. The results showed that the use of P. roqueforti in the manufacture of mould‐ripened Civil cheese has significant impact on the volatile profiles and sensory attributes.