The effects of incorporating wild‐type strains of Lactococcus lactis into Turkish white‐brined cheese (Beyaz peynir) on the fatty acid and volatile content

The development of free fatty acids (FFA) and volatile flavour compounds in the Turkish white‐brined cheese Beyaz peynir made by using three wild strains of Lactococcus lactis subsp. lactis was investigated over 90 days. Results showed that production of both FFA and flavour compounds in the control (PK1) and experimental cheeses (MBLL9, MBLL23 and MBL27) was strain dependent. The hydrolysis of milk fat was more evident in the cheese made using Lc. lactis subsp. lactis MBL27. Considering the production of fat breakdown compounds and acidification activities of the strains MBLL23 and MBL27, the combination of these strains could be proposed for the production of white‐brined cheese.     

Effect of the addition of nitrate to milk on the formation of volatile N-nitrosamines and apparent total N-nitroso compounds

 Saint-Paulin, a French semihard cheese, was manufactured from milk with and without added NO₃ ^–. Reference and experimental cheeses were analysed at different stages of ripening for the presence of apparent total N-nitroso compounds (ATNC) by chemical denitrosation and chemiluminescence detection (thermal energy analyser). The fate of NO₃ ^– and NO₂ ^–was also scrutinized. The levels of ATNC and of volatile N-nitrosamines were followed during ripening. After 60 days of ripening, ATNC were detected at concentrations of 27 μg NO-N/kg and 64 μg NO-N/kg in the cheeses obtained from milk with and without added NO₃ ^–, respectively. The NO₃ ^– contents of both cheeses were nearly the same, and below 5 mg/kg. The occurrence of NO₂ ^–was not observed. No relationship was found between the NO₃ ^– contents and the contamination of the cheeses by volatile N-nitrosamines. At the beginning of ripening, the cheeses manufactured with added NO₃ ^- showed high levels of ATNC (mean value 5800 μg N-NO/kg with large variations of 570–15210 μg NO-N/kg). These ATNC contents rapidly decreased during the first days of ripening (96%), but decreased much more slowly during the following days. An hypothetical mechanism, attempting to explain the disappearance of ATNC, involving the formation of alkylated species in the cheese was proposed. Received: 30 March 1998 / Revised version: 7 October 1998     

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.     

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.     

Potential impact of dairy yeasts on the typical flavour of traditional ewes' and goats' cheeses

The contribution of Debaryomyces hansenii, Kluyveromyces lactis and Kluyveromyces marxianus strains to the typical flavour of traditional ewes' and goats' cheeses was assessed. Fourteen yeast strains were grown in liquid medium mimicking cheese composition and volatile compounds were identified by gas chromatography-mass spectrometry. Yeasts were able to produce key volatile compounds characteristic of the cheeses from which they were isolated. Inter-species and inter-strain variations were observed. Under the conditions tested, D. hansenii produced the lowest levels of volatile compounds, with large intra-strain variations. Kluyveromyces strains primarily produced esters and alcohols. K. marxianus strains were associated with the production of acids, ethyl decanoate, 1-propanol and benzaldehyde, whereas K. lactis was correlated with the presence of ketones, ethyl acetate and secondary alcohols. In conclusion, this study shows the heterogeneous potential of dairy yeasts to contribute to final cheese flavour.     

Influence of a defined-strain starter and Lactobacillus plantarum as adjunct culture on volatile compounds and sensory characteristics of Manchego cheese

Three batches of Manchego cheese were manufactured using one of the following starter culture systems: (1) a defined strain starter culture comprising Lactococcus lactis subsp. lactis and Leuconostoc mesenteroides subsp. dextranicum; (2) the above-defined strain starter culture and an adjunct culture (Lactobacillus plantarum), all these strains being isolated from high-quality Manchego cheeses and (3) a commercial starter consisting of two strains of Lactococcus lactis. Differences in volatile profile and the sensory characteristics of these cheeses were studied. After 4 months of ripening, the two batches of cheese made with the defined strain starter cultures obtained the highest scores for sensory attributes and for the overall impression. Additionally, Purge & Trap and SDE analysis showed a more complex volatile profile in these cheeses than in those made with the commercial starter. Extending the maturation time to 8 months for cheeses made with the defined starter cultures led to significant higher levels of free fatty acids and ethyl esters in those cheeses made without adjunct culture. However, panelists did not find significant differences among the sensory characteristics of the two cheeses.     

Accelerated ripening of Ras cheese using cell free extract,freeze- and heat-shocked Leuconostoc spp. cultures

Ras cheese was manufactured with cell free extract, freeze- and heat-shocked cultures of Leuconostoc spp. to enhance flavour development and accelerated ripening. Cheese analysis (pH, acidity, dry matter, fat, protein, soluble nitrogen, volatile acidity, free fatty acids) were carried out for 3 months. No significant differents were observed between the experiment cheeses and control, however, the cheese flavour was enhanced in cheeses with addition of heat treated Leuconostoc cells. Bitter taste was decreased in all experimental cheeses.     

Proteolysis of Mahon cheese as affected by acoustic-assisted brining

 Mahon cheeses were brined in the presence of an ultrasonic field and ripened during 75 days at 12  °C and 85% RH. Secondary proteolysis (water-soluble N, non-protein N, and free amino acids) was measured and compared to that obtained for cheeses conventionally brined. There were no differences in water-soluble and non-protein N attributable to the brining treatment. However, cheeses acoustically brined exhibited higher concentrations of free amino acids. The release of total free amino acids was more pronounced during the first 15 days of ripening for both types of brining treatments. The changes in proteolysis (free amino acids) during cheese ripening caused by acoustic-assisted brining are indicative of a higher extent of proteolysis and may also improve cheese flavor. Received: 13 March 2000     

Compositional,biochemical and textural changes during ripening of Tulum cheese made with different coagulants

In the present study, biochemical, chemical and texture changes in Tulum cheeses made using calf rennet and microbial rennets (Aspergillus niger protease and Rhizomucor miehei protease) were compared during ripening for up to 90 days. A total of 15 free fatty acids (FFAs) were detected in the cheese samples. The peroxide values (PV) of the cheeses increased significantly (P < 0.05) during ripening and the cheese made with calf rennet had the highest PV. Proteolysis in the cheeses increased as the ripening time increased. α_s1‐casein and β‐casein degradation was higher in cheeses manufactured with R. miehei protease. Cheeses made with calf rennet were significantly (P < 0.05) harder, more adhesive, more cohesive and more resilient than those made with microbial rennet.     

High-Pressure Processing for the Control of Lipolysis,Volatile Compounds and Off-odours in Raw Milk Cheese

Build-up of flavour compounds throughout ripening of raw milk cheeses may result in strong over-ripening notes during refrigerated storage. In order to control the formation of free fatty acids (FFAs) and volatile compounds, and the appearance of off-odours, raw milk cheeses were high-pressure-processed (HPP) 21 or 35 days after manufacture at 400 or 600 MPa. Ripening proceeded at 8 °C until day 60 and, afterwards, cheeses were held at 4 °C until day 240. The effect of HPP on the formation of FFAs and volatile compounds was dependent on pressure level and cheese age at the time of treatment. On day 60, acetic and propionic acids, branched-chain FFAs and short-chain FFAs showed the lowest (p?<?0.05) concentrations in cheeses treated at 400 or 600 MPa on day 21, while medium- and long-chain FFAs were at similar levels in all cheeses. HPP influenced significantly (p?<?0.05) 84 out of the 94 volatile compounds found in cheese. On day 60, the lowest (p?<?0.05) concentrations of acids, alcohols and esters were recorded for cheeses treated at 400 or 600 MPa on day 21, and the lowest (p?<?0.05) concentrations of ketones for cheeses treated at 400 MPa on days 21 or 35. On day 240, all HPP cheeses showed lower (p?<?0.05) concentrations of aldehydes, esters and, particularly, sulphur compounds than control cheese, which exhibited putrid and rancid off-odours from day 120 onwards. Principal component analysis combining FFAs and volatile compounds discriminated 240-day control cheese from 120-day control cheese and both from the rest of cheeses.     

Characterization of Italian cheeses ripened under nonconventional conditions

Four Italian cheeses (Casciotta di Urbino, Barricato San Martino, Vento d’Estate, and Ubriaco di Raboso) nonconventionally ripened under different plant materials (walnut leaves, herbs, hay, and wine by-products, respectively) were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for gross composition were rather similar. Because primary starters were not used for manufacture, the endogenous lactic acid bacteria were mainly present (7.0 to 9.0 log₁₀ cfu/g). Except for Lactobacillus paracasei and Leuconostoc mesenteroides, which were commonly identified in 3 cheeses, Lactococcus lactis, Enterococcus sanguinicola, Lactobacillus brevis, Enterococcus durans/Enterococcus faecium, Lactobacillus plantarum, and Weissella cibaria/Weissella confusa were variously found in the 4 cheeses. Random amplification of polymorphic DNA-PCR analysis showed the biodiversity among the strains, and the species of lactobacilli were in part grouped according to their origin. As shown by the principal component analysis of reverse-phase fast protein liquid chromatography data for the pH 4.6-soluble fractions and by the determination of free AA, the secondary proteolysis of Barricato San Martino and Vento d’Estate mainly differed from the other 2 cheeses. Purge-and-trap and solid-phase microextraction were coupled with gas chromatography-mass spectrometry to determine volatile compounds. Vento d’Estate showed the highest levels of almost all chemical classes, and Casciotta di Urbino was characterized by a very low level of volatile components. Esters, ketones, and terpenes were the chemical classes that mainly differentiated the cheeses. Several volatile compounds seemed to be released directly from the plant materials used for ripening, especially terpenes for Vento d’Estate cheese. The lowest level of volatile free fatty acids was found in Casciotta d’Urbino, in which rennet paste was not used during manufacture. The highest concentration of free fatty acids, especially butyric and caproic acids, was found in Vento d’Estate cheese.     

Flavour precursor development in Cheddar cheese due to lactococcal starters and the presence and lysis of Lactobacillus helveticus.

The rapid release of intracellular enzymes due to autolysis of lactic acid bacteria in the cheese matrix has been shown to accelerate cheese ripening. The objective of this work was to investigate the evolution of the flavour precursors, individual free amino acids (FAAs), free fatty acids (FFAs) and volatile compounds that contribute to the sensory profiles of cheeses at 2, 6 and 8 months of ripening in Cheddar cheese manufactured using starter systems which varied with respect to their autolytic properties. Starter system A contained a blend of two commercial Lactococcus lactis strains (223 and 227) which had a low level of autolysis. System B was identical to A but also included a highly autolytic strain of Lactobacillus helveticus (DPC4571). System C contained only strain DPC4571. Levels of all individual FAAs were elevated in cheeses B and C relative to A after 2 months of ripening. By 8 months of ripening the main FAA were glutamate, leucine, lysine, serine, proline and valine. Levels of C_6:0, C_8:0, C_12:0 and C_18:0 fatty acids did not vary greatly over ripening, while levels of C_4:0, C_10:0, C_14:0, C_16:0 and C_18:1 were elevated in cheeses B and C. Principal component analysis of the headspace volatiles separated cheese A from cheeses B and C. Cheeses B and C had highest levels of dimethyl disulphide, carbon sulphide, heptanal, dimethyl sulphide, ethyl butanoate, 2-butanone, and 2-methyl butanal and were described as having a ‘caramel’ odour and ‘sweet’, ‘acidic’ and ‘musty’ flavour. Cheese A had highest levels of 2-butanol, 2-pentanone, 2-heptanone, 1-hexanol and heptanal and was described as having a ‘sweaty/ sour’ odour and ‘soapy’, ‘bitter’ and ‘mouldy’ flavour. The results highlight the impact of starter lactococci on flavour precursor development and the positive effect of Lb. helveticus and the lysis of this strain on enhancing levels of substrate and flavour precursors early during ripening resulting in early flavour development.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

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

Twenty‐two free amino acid (FAA) concentrations were observed during manufacture (7 days) and ripening period (42 days follow‐up) of Olomoucké tvar??ky (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 < 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 < 0.05) or decreased (e.g. dimethyldisulphide, methanethiol, 2‐phenylethylacetate, methylbutyric acid; P < 0.05) over cheese ageing. The results gave information about the development of sensory active substances and its precursors in Olomoucké tvar??ky during ripening. In conclusion, we found that free amino acid concentrations and sulphur compounds are positive with improved flavour.     

Utilization of freeze-shocked lactobacilli for enhancing flavour development of Ras cheese

Freeze-shocked cultures of Lactobacillus helveticus or Lactobacillus casei were added at levels of 1% and 2% to Ras cheese milk prior to renneting as an adjunct starter to enhance flavour development of cheese. These additives did not affect the gross chemical composition of the cheeses but increased the formation of soluble nitrogenous compounds, free volatile fatty acids, the flavour intensity and improved the body characteristic. Also, the counts of bacterial groups (total, proteolytic and lipolytic) of the cheese treated with freeze-shocked lactobacilli were higher than in the control. Moreover, the ripening period was reduced to be 2 months compared with 4 months required for the control cheese. Also, using freeze-shocked culture of L. helveticus was the most effective in this respect.     

High-pressure processing decelerates lipolysis and formation of volatile compounds in ovine milk blue-veined cheese

Enzyme-rich cheeses are prone to over-ripening during refrigerated storage. Blue-veined cheeses fall within this category because of the profuse growth of Penicillium roqueforti in their interior, which results in the production of highly active proteinases, lipases, and other enzymes responsible for the formation of a great number of flavor compounds. To control the excessive formation of free fatty acids (FFA) and volatile compounds, blue-veined cheeses were submitted to high-pressure processing (HPP) at 400 or 600 MPa on d 21, 42, or 63 after manufacture. Cheeses were ripened for 30 d at 10°C and 93% relative humidity, followed by 60 d at 5°C, and then held at 3°C until d 360. High-pressure processing influenced the concentrations of acetic acid and short-chain, medium-chain, and long-chain FFA. The effect was dependent on treatment conditions (pressure level and cheese age at the time of treatment). The lowest concentrations of acetic acid and FFA were recorded for cheeses treated at 600 MPa on d 21; these cheeses showed the lowest esterase activity values. Acetic acid and all FFA groups increased during ripening and refrigerated storage. The 102 volatile compounds detected in cheese belonged to 10 chemical groups (5 aldehydes, 12 ketones, 17 alcohols, 12 acids, 35 esters, 9 hydrocarbons, 5 aromatic compounds, 3 nitrogen compounds, 3 terpenes, and 1 sulfur compound). High-pressure processing influenced the levels of 97 individual compounds, whereas 68 individual compounds varied during refrigerated storage. Total concentrations of all groups of volatile compounds were influenced by HPP, but only ketones, acids, esters, and sulfur compounds varied during refrigerated storage. The lowest total concentrations for most groups of volatile compounds were recorded for the cheese pressurized at 600 MPa on d 21. A principal component analysis combining total concentrations of groups of FFA and volatile compounds discriminated cheeses by age and by the pressure level applied to HPP cheeses.     

Microbial, chemical and sensorial variables of the Spanish traditional blue-veined Cabrales cheese, as affected by inoculation with commercial Penicillium roqueforti spores

This paper reports the technological effects of inoculating Cabrales cheese (a traditional, Spanish, blue-veined cheese) with Penicillium roqueforti spores. Three batches of inoculated Cabrales cheese were manufactured and a number of their microbial and biochemical variables recorded. The results were compared with those obtained for three batches of control cheese made using traditional technology (i.e., adding neither starter cultures nor fungal spores). Although mould and yeast populations grew more quickly in the inoculated cheeses, their normally dominant and representative microbial populations were not affected neither was their gross biochemical composition changed. The variations observed were thought to be caused by the uncontrolled environmental conditions of manufacture and ripening. The development of free amino acids and volatile compounds was significantly increased at 30 days in the inoculated cheeses, although the values for both types of cheese were almost identical at 90 days. The inoculated cheeses obtained higher scores in a hedonistic sensorial evaluation. Thus, inoculation improved the standardization and quality of the cheese.     

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.