Cheese Slurry Research Articles

Acceleration of proteolysis, flavour development and enhanced bioactivity in a model cheese using Kuflu cheese slurry: An optimisation study

This study aimed to use Kuflu (a mould-ripened cheese) cheese slurry to accelerate ripening, improve biological activity and flavour development in a model cheese in terms of proteolysis and volatile compounds. Response surface methodology (RSM) was employed for the model cheese to determine higher proteolysis and volatile development level during ripening as a function of Kuflu cheese slurry addition level (0–5 %), salt concentration (1–3 %) and ripening temperature (5–15 °C). The highest aminopeptidase activities (0.140 and 0.187 OD/g per hour) were determined in 15-day-old samples containing 3 % and 5 % Kuflu cheese slurry, respectively. Also, the use of Kuflu cheese slurry, regardless of ripening, caused an increase in ABTS*+ antioxidants, angiotensin-converting enzyme (ACE)-inhibition activity and volatile compounds in model cheeses. The sensory evaluation indicated that the use of 3 % (w/w) Kuflu cheese slurry, storage temperature 10 °C for 15 days provided better flavour, odour, texture, colour, appearance and overall acceptability. In conclusion, using Kuflu cheese slurry for model cheese production enhanced the level of proteolysis and volatile flavour composition with shortened ripening time.

Incorporation of Different Cheese Slurries into Retentate of Ultra-filtrated White Soft Cheese for Enhancing Flavor and Quality Improvement

ABSTRACTOne of the most important criteria in any type of cheese is its flavor and texture, which consequently affect its quality, consumer choice and acceptance. The ultra-filtrated (UF) white soft cheese is one of the very popular cheese types in the Mediterranean region. This type of cheese has some properties that do not meet the consumer preferences because of the lack in its flavor and also the texture is not spreadable. So this study aimed to improve the quality and enhancing theflavor of UF-white soft cheese by incorporating different cheese slurries into the prepared retentate for UF-white cheese making and compared with UF- cheese control. The slurries of pickledDomiatti, Roquefort or Mish cheeses were incorporated separately into the cheese retentatewith different levels (6, 9 or 12%). Chemical, microbiological, rheological and sensory properties of all resultant UF-white cheese treatments and control were studied during the cold storage at 6+1oC. The results showed high values for acidity, total nitrogen, water soluble nitrogen, total volatile fatty acids, salt, ash, fat and total solids in cheese treatments comparing with control during the storage period. Rheological parameters in all cheese treatments were decreased during storage period. The flavor and textureof UF-white soft cheese treatments were improved by using the different cheese slurries. The favorite slurry type was registered for Domiatti cheese,in all added levels as it showsthe highest total scores for sensory evaluationalong the storage periodcomparing to other treatments andcontrol.

Effect of two thermoresistant non-starter lactic acid bacteria strains on volatilome profile during Cheddar ripening simulation

Dairy farm management practices can modify milk microbiota and therefore modulate non-starter lactic acid bacteria (NSLAB) found in cheese. These NSLAB can cause organoleptic defects. This study aimed to investigate the impact of two potential NSLAB in Cheddar cheesemaking: Lactiplantibacillus plantarum RKG 2-212 a strain isolated both in corn silage and raw milk, and Lactobacillus delbrueckii RKG R10, a strain isolated after pasteurisation of milk from a farm using grass and legume silage, and corn silage. The whole genome of these two lactobacilli was first sequenced. Then, the thermoresistance was evaluated after treatment at 60 °C for 5 min and compared to reference strains. Both lactobacilli were highly thermoresistant compared to other three lactic acid bacteria which are Lactococcus lactis subsp. cremoris ATCC 19257 and SK11, and L. plantarum ATCC 14917 (P < 0.0001). They lost less than 1 log cfu/mL (Δlog) and their genome contained a great number of copy number of genes coding for heat shock protein. During a Pearce test activity simulating Cheddar cheesemaking, the two lactobacilli did not show interaction with the starter Lcc. lactis subsp. cremoris SK11, and their population remained stable. During a ripening simulation, L. delbrueckii RKG R10 had a slight loss in viability in cheese slurry samples incubated at 30 °C for 12 d. However, L. plantarum RKG 2–212 had considerable growth, from 6.51 to 8.3 log cfu/g. This growth was associated with the acidification of the slurries (P < 0.0001). The presence of the lactobacilli modified the profile of volatile compounds evaluated by gas chromatography–mass spectrometry, accounting for 10.7% of the variation. The strain L. plantarum RKG 2-212 produced volatile compounds in greater quantity that could be associated with organoleptic defects such as acetic acid and 2-methylbutyraldehyde. Therefore, silage can be a vector of thermoresistant lactic acid bacteria for milk which can lead to flavor defects in cheese.

Impact of Nisin and Nisin-Producing Lactococcus lactis ssp. lactis on Clostridium tyrobutyricum and Bacterial Ecosystem of Cheese Matrices.

Clostridium tyrobutyricum spores survive milk pasteurization and cause late blowing of cheeses and significant economic loss. The effectiveness of nisin-producing Lactococcus lactis ssp. lactis 32 as a protective strain for control the C. tyrobutyricum growth in Cheddar cheese slurry was compared to that of encapsulated nisin-A. The encapsulated nisin was more effective, with 1.0 log10 reductions of viable spores after one week at 30 °C and 4 °C. Spores were not detected for three weeks at 4 °C in cheese slurry made with 1.3% salt, or during week 2 with 2% salt. Gas production was observed after one week at 30 °C only in the control slurry made with 1.3% salt. In slurry made with the protective strain, the reduction in C. tyrobutyricum count was 0.6 log10 in the second week at 4 °C with both salt concentration. At 4 °C, nisin production started in week 2 and reached 97 µg/g after four weeks. Metabarcoding analysis targeting the sequencing of 16S rRNA revealed that the genus Lactococcus dominated for four weeks at 4 °C. In cheese slurry made with 2% salt, the relative abundance of the genus Clostridium decreased significantly in the presence of nisin or the protective strain. The results indicated that both strategies are able to control the growth of Clostridium development in Cheddar cheese slurries.

Impact of Some Probiotic Bacteria on Flavor and Quality of Novel Cheese Slurry

Impact of Some Probiotic Bacteria on Flavor and Quality of Novel Cheese Slurry

Effects of the Essential Oil from Origanum vulgare L. on Survival of Pathogenic Bacteria and Starter Lactic Acid Bacteria in Semihard Cheese Broth and Slurry

This study assessed the inhibitory effects of the essential oil from Origanum vulgare L. (OVEO) on Staphylococcus aureus, Listeria monocytogenes, and a mesophilic starter coculture composed of lactic acid bacteria (Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris) in Brazilian coalho cheese systems. The MIC of OVEO was 2.5 μl/ml against both S. aureus and L. monocytogenes and 0.6 μl/ml against the tested starter coculture. In cheese broth containing OVEO at 0.6 μl/ml, no decrease in viable cell counts (VCC) of both pathogenic bacteria was observed, whereas the initial VCC of the starter coculture decreased approximately 1.0 log CFU/ml after 24 h of exposure at 10°C. OVEO at 1.25 and 2.5 μl/ml caused reductions of up to 2.0 and 2.5 log CFU/ml in S. aureus and L. monocytogenes, respectively, after 24 h of exposure in cheese broth. At these same concentrations, OVEO caused a greater decrease of initial VCC of the starter coculture following 4 h of exposure. Higher concentrations of OVEO were required to decrease the VCC of all target bacteria in semisolid coalho cheese slurry compared with cheese broth. The VCC of Lactococcus spp. in coalho cheese slurry containing OVEO were always lower than those of pathogenic bacteria under the same conditions. These results suggest that the concentrations of OVEO used to control pathogenic bacteria in semihard cheese should be carefully evaluated because of its inhibitory effects on the growth of starter lactic acid cultures used during the production of the product.

Utilization of a New and Improved Dressing for Implanted Ports

The volatile organic compound (VOC) profile of a Swiss cheese curd slurry system, with and without addition of reduced glutathione (GSH), was investigated on a daily basis for six days of incubation at 30 °C. The VOC profiles of commercial Swiss cheese samples from different stages during manufacture (after press, end of pre-cool, end of warm room and at cut) were also measured. Using the volatiles produced, the time scale of the slurry was matched to that of conventional ripening to determine which day of accelerated ripening corresponded to each stage of commercial ripening. The profiles of most of the VOCs in the slurry system with GSH more closely matched the profiles at the different stages of Swiss cheese ripening than the slurry system without GSH. Moreover, the headspace concentrations of volatiles that are considered to produce off-flavors were significantly decreased in the Swiss cheese slurry system with GSH.

Suppression of propanoic acid, acetic acid and 3-methylbutanoic acid production by other volatiles in a Swiss cheese curd slurry system

The effect of the addition of 5–100 ppm 2,3-butanedione, butanoic acid, methyl mercaptan, ethyl butanoate, diethyl sulfide, 3-methylbutanoic acid, acetaldehyde and ethanol on production of propanoic acid, acetic acid and 3-methylbutanoic acid in a Swiss cheese slurry system was investigated. Enumeration of propionic acid bacteria (PAB) was done to monitor the microbial count in the systems. A Swiss cheese slurry system was used to simulate cheese manufacturing based on accelerated ripening for a 6-day incubation period. The headspace concentrations of propanoic acid, acetic acid and 3-methylbutanoic acid were significantly decreased by the addition of 2,3-butanedione, butanoic acid, and methyl mercaptan, but were generally unaffected by ethyl butanoate, diethyl sulfide, 3-methylbutanoic acid, acetaldehyde and ethanol. Microbial enumeration also showed that there was a significant reduction of PAB in slurry systems with 100 ppm 2,3-butanedione, butanoic acid, and methyl mercaptan.

Volatile organic compounds of a Swiss cheese slurry system with and without added reduced glutathione, compared with commercial Swiss cheese

The volatile organic compound (VOC) profile of a Swiss cheese curd slurry system, with and without addition of reduced glutathione (GSH), was investigated on a daily basis for six days of incubation at 30 °C. The VOC profiles of commercial Swiss cheese samples from different stages during manufacture (after press, end of pre-cool, end of warm room and at cut) were also measured. Using the volatiles produced, the time scale of the slurry was matched to that of conventional ripening to determine which day of accelerated ripening corresponded to each stage of commercial ripening. The profiles of most of the VOCs in the slurry system with GSH more closely matched the profiles at the different stages of Swiss cheese ripening than the slurry system without GSH. Moreover, the headspace concentrations of volatiles that are considered to produce off-flavors were significantly decreased in the Swiss cheese slurry system with GSH.

Thermosonication versus thermal processing of skim milk and beef slurry: Modeling the inactivation kinetics of psychrotrophic Bacillus cereus spores

Non-thermal processed foods are generally cold stored and distributed. The use of ultrasound for food preservation has attracted the interest of many research groups. In the current study, the thermosonication (TS, simultaneous ultrasound and thermal process) inactivation of psychrotrophic Bacillus cereus spores was investigated (24kHz, 210μm, 0.33W/mL or W/g). First, the effectiveness of a 1.5min TS process at 70°C in skim milk, beef slurry, cheese slurry, and rice porridge was investigated. The TS was more effective than sole thermal treatment in reducing B. cereus spores in rice porridge, beef slurry and cheese slurry by 7, 6, and 4 fold, respectively. Then, the first-order D- and z-values for TS and thermal processing in skim milk and beef slurry, and the best model to fit TS inactivation of B. cereus spores in beef slurry were determined. The D70°C-values in skim milk were 2.9min for TS and 8.6min for the thermal treatment. And in beef slurry, values of 0.4min for TS and 2.3min for thermal were estimated. It was found that the Log-logistic model better described the TS spore inactivation in beef slurry. The ultrasound technology required 20–30°C lower temperatures for the same spore inactivation, which resulted in better food quality and energy saving gains.

Infrared Thermography for Monitoring of Freeze-Drying Processes: Instrumental Developments and Preliminary Results

Coupling an infrared (IR) camera to a freeze dryer for on-line monitoring of freeze-drying cycles is described for the first time. Normally, product temperature is measured using a few invasive Pt-100 probes, resulting in poor spatial resolution. To overcome this, an IR camera was placed on a process-scale freeze dryer. Imaging took place every 120 s through a Germanium window comprising 30,000 measurement points obtained contact-free from −40°C to 25°C. Results are presented for an empty system, bulk drying of cheese slurry, and drying of 1 mL human serum in 150 vials. During freezing of the empty system, differences of more than 5°C were measured on the shelf. Adding a tray to the empty system, a difference of more than 8°C was observed. These temperature differences probably cause different ice structures affecting the drying speed during sublimation. A temperature difference of maximum 13°C was observed in bulk mode during sublimation. When drying in vials, differences of more than 10°C were observed. Gradually, the large temperature differences disappeared during secondary drying and products were transformed into uniformly dry cakes. The experimental data show that the IR camera is a highly versatile on-line monitoring tool for different kinds of freeze-drying processes. © 2014 European Union 103:2088–2097, 2014

Determination of optimal conditions for γ-aminobutyric acid production by Lactococcus lactis ssp. lactis

The biocompatibility of nine proteinase-negative strains of Lactococcus lactis ssp. lactis with the ability to produce γ-aminobutyric acid (GABA) and four proteinase-positive (Prt+) strains of Lactococcus lactis ssp. cremoris under simulated Cheddar cheese manufacturing conditions resulted in the selection of the Prt+ strain L. lactis ssp. cremoris W62 for mixed cultures with the nine GABA strains. Of the nine mixed cultures inoculated in milk enriched with glutamate, two blends produced between 7.0 and 7.5 mg of GABA per 100 mL of milk. The effect of pH, salt-to-moisture (SM) ratio, and glutamate concentration on the production of GABA was evaluated using cheese slurry models. The production of GABA increased with glutamate concentration but was lower for a SM level of 4.5%. Low pH was the key factor for GABA production. Combining the optimal factors (pH 4.8, 3.0 mg glutamate, SM 3.0%) gave 23 mg GABA per 30 g of cheese curd.

Gamma-aminobutyric acid-producing abilities of lactococcal strains isolated from old-style cheese starters

A previous study showed the ability of old-style cheese starters to produce large amounts of γ-aminobutyric acid (GABA). This work reports the identification of GABA-producing strains and the effect of the main cheese matrix parameters (NaCl, glutamic acid, pH, oxygen) having an influence on GABA production. Out of a total of 50 individual bacterial strains contained in two old-style cheese starters, nine were able to produce GABA and were identified as either Lactococcus lactis ssp. lactis or L. lactis ssp. lactis biovar diacetylactis. Strains ULAAC-A13 and ULAAC-A23 were able to produce up to 500 mg of GABA per 100 mL of fermented milk containing 2% NaCl and 367 mg per 100 mL of glutamate. Moreover, the low residual glutamate concentration indicates the almost total conversion of glutamate into GABA. GABA was also detected in four commercial cheeses at concentrations varying from 10 to 97 mg of GABA per 30 g of cheese and at a concentration of 29 mg of GABA per 30 g of a cheese slurry ripened with ULAAC-A old-style starter. In that cheese slurry, GABA concentrations were above the levels previously proven to be effective for lowering blood pressure in humans. Both individual GABA-producing strains or the old-style starters containing the GABA strains seem to be promising for GABA production in hard or semi-hard cheeses with prevailing conditions for GABA production.

Influence of Adjuncts as Debittering Aids on the Sensory and Biochemical Properties of Enzyme Modified Cheese-Base

An attempt has been made to accelerate the flavour development in cheese slurry with the help of exogenous proteolytic and lipolytic enzymes (1:1 proportion, each at the rate of 0.025 % by weight of cheese-base) and ripening at elevated temperatures (i.e. 20 ± 1 °C) for up to 12 days. Bitterness, the necessary consequence of accelerated cheese ripening, has been the main objective of the present investigation. Adjunct cultures Lactobacillus casei and Lactobacillus helveticus were used as debittering aids. The debittering activity was monitored using electrophoretic pattern and sensory evaluation of the product. Freeze-shocked adjunct Lactobacillus helveticus produced enzyme-modified cheese slurry with no detectable bitterness. The usage of adjunct cultures either viable or attenuated, ripening period and interactions amongst these parameters had significant (P < 0.05) influence on all of the sensory characteristics monitored.

Impact of processing steps on the composition of volatile compounds in cheese powders

Changes in the composition of volatile compounds during processing of cheese powders, made from Emmental and Danbo cheese were analysed by dynamic headspace gas chromatography–mass spectrometry. Samples comprised cheese, melted cheese slurry, the slurry heat treated using three different time and temperature combinations, and the spray‐dried cheese powder. About 100 volatile compounds were identified. During melting of the cheese the level of some volatile compounds increased significantly; heat treatment mainly leads to a loss of compounds and spray drying leads to a substantial reduction of volatile compounds, with the exception of a range of aldehydes that increased. The final cheese powders could, however, be distinguished according to cheese type.

Characterization of aromatic properties of old-style cheese starters

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30°C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of γ-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. γ-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects.

Influence of adjuncts as a debittering aids in encountering the bitterness developed in cheese slurry during accelerated ripening

Summary An attempt was made to accelerate the flavour development in cheese base with the help of exogenous proteolytic and lipolytic enzymes (1:1 proportion, each at the rate of 0.025% by weight of cheese-base) and ripening at elevated temperatures (i.e. 20 ± 1 °C) for up to 12 days. To counter the bitterness developed, adjunct cultures were used: viable or attenuated (freeze-shocked or heat shocked). Study of biochemical characteristics, electrophoretic pattern and sensory evaluation of the product were carried out. An acceptable enzyme-modified, lightly salted cheese base was obtained using 0.025% each of proteolytic and lipolytic enzymes, along with 5% starter culture and adjuncts followed by ripening up to 12 days. Freeze-shocked adjunct Lactobacillus helveticus produced enzyme-modified cheese base with no detectable bitterness. The usage of exogenous enzymes, temperature of ripening, ripening period and interactions amongst these parameters had significant (P < 0.01) influence on all of the biochemical characteristics monitored.

Proteolysis of Cheese Slurry Made from Pulsed Electric Field-Treated Milk

Raw milk cheeses have unique flavor and texture characteristics not obtainable in cheeses made from pasteurized milk. However, cheeses made from pasteurized milk are widespread, primarily for public health reasons. Pulsed electric field (PEF) treatment as a non-thermal pasteurization method has shown its ability to keep the flavor and natural characteristics of food samples intact, thus providing advantage over conventional heat processing. In this study, PEF treatment was performed in a continuous treatment chamber, consisting of two parallel stainless steel electrodes separated by a 50-mm-thick insulator. A 30-kV pulse generator was used to deliver bi-polar square waveform electric field to milk sample. Pulse width was 2 µs; pulse frequency was 2 Hz, and up to 120 pulses were applied. Cheese curds were made from raw milk, pasteurized milk, and PEF-treated milk, and their proteolysis processes were compared using curd slurry incubated at 30 °C for 5 days. The profiles of water-soluble peptides were measured using an reversed-phase high-performance liquid chromatography (RP-HPLC) system. The concentration of free amino acids was measured by Cd–ninhydrin method. Results indicated that PEF-treated milk has intermediate proteolysis profiles between raw milk and pasteurized milk in terms of peptide and free amino acid concentration. The results showed the potential of making high-quality cheeses by PEF treatment without sacrificing the natural characteristics of the cheeses.

Proteolysis development in enzyme-modified Cheddar cheese using natural and recombinant enzymes of Lactobacillus rhamnosus S93

Proteolysis in enzyme-modified cheese was investigated with natural crude enzyme or recombinant aminopeptidase, both derived from Lactobacillus rhamnosus S93 in the presence of a commercial proteinase, Neutrase. For production of enzyme-modified cheeses, a cheese slurry was produced and pre-incubated with Neutrase. Natural enzyme or recombinant aminopeptidase (50 units 200 g −1 slurry) was added alone or in combination to the cheese slurries, which were then incubated anaerobically under vacuum at 37 °C for 1, 3 and 6 d. The greatest levels of phosphotungstic acid soluble nitrogen and free amino acids were observed in the enzyme-modified cheese containing natural enzyme followed by the one treated with a combination of the natural enzyme and recombinant aminopeptidase. The enzyme-modified cheese containing the recombinant aminopeptidase alone resulted in the complete disappearance of proline after 1 d of maturation time.

Isolation of anticlostridially active lactobacilli from semi-hard cheese

The group of 7 strains of facultatively heterofermentative lactobacilli (FHL) of the non starter lactic acid bacteria (NSLAB) isolated from semi-hard cheeses using a well agar diffusion assay possessed a different level of inhibition activity against 16 different strains of &lt;I&gt;Clostridium&lt;/I&gt; sp. belonging to the species &lt;I&gt;Cl. butyricum, Cl. tyrobutyricum, Cl. beijerinckii&lt;/I&gt;, and &lt;I&gt;Cl. sporogenes&lt;/I&gt;. Two selected strains with the production of partially indentified anticlostridially active inhibitory substances, &lt;I&gt;Lb. paracasei&lt;/I&gt; ST68 (producing hydrogen peroxide) and &lt;I&gt;Lb. paracasei&lt;/I&gt; 171R2 (producing bacteriocin and hydrogen peroxide), were tested for the inhibition activity against gas producing &lt;I&gt;Cl. butyricum&lt;/I&gt; 10702 and &lt;I&gt;Cl. tyrobutyricum&lt;/I&gt; 184 in cheese slurry. The effects of both strains were different in reducing the numbers of gas producing &lt;I&gt;Cl. butyricum&lt;/I&gt; 10702 by &gt; 3 log cycles and &lt;I&gt;Cl. tyrobutyricum&lt;/I&gt; 184 by &gt; 1 log cycles in cheese slurry during the tested storage periods of 24 days at 13°C. The &lt;I&gt;Cl. tyrobutyricum&lt;/I&gt; strains isolated from spoiled cheese were identified by species-specific PCR for &lt;I&gt;Cl. tyrobutyricum. &lt;/I&gt;