Cheese Matrix Research Articles

Potential application of ginger, clove and thyme essential oils to improve soft cheese microbial safety and sensory characteristics

Due to consumers growing concerns about synthetic preservatives, essential oils (EOs) come into the focus of pharmaceutical and food applications as natural alternatives because of their inherent antimicrobial activity. However, EOs food applications have been challenged by their strong aroma that adversely affects consumers acceptability. In this study, EOs of Zingiber officinale (ginger), Syzygium aromaticum (clove), and Thymus vulgaris (thyme) were extracted and assessed for their potential use to produce cheese with high degree of microbial safety and sensory acceptability. Phytochemical profiling showed camphene and zingiberene as major constituents in ginger oil, whereas thymol and eugenol represented the chief volatiles in thyme and clove, respectively. The EOs antimicrobial activity against seven strains of pathogenic and spoilage bacteria, yeast and mold revealed MIC of 0.001%. Additionally, studied EOs demonstrated interesting safety profile displaying good to very weak cytotoxicity on human hepatocellular carcinoma (HepG2) with CC50 6.31–452.95 μg/mL and very low cytotoxicity on normal human lung fibroblasts (WI-38) with CC50 728.94–841.66 μg/mL. Sensory characterization of EOs-fortified laboratory manufactured fresh soft cheese displayed scores significantly higher than control samples (P < 0.001) in relation to overall acceptability. Viability study of Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa in fortified cheese matrix showed complete reduction of S. aureus at the end of first and second weeks of storage of thyme and ginger fortified cheese, respectively, and about 50% reduction of P. aeruginosa by the end of storage period. This study opens interesting new perspectives for the agro-industrial applications of EOs as natural preservatives.

Lipoprotein Particle Size Distributions in Response to a 6-Week Dietary Intervention Using Different Dairy Food Matrices Including Cheese and Butter

Abstract Objectives Most dietary guidelines recommend saturated fat (SFA) intakes to be &amp;lt; 10% of total energy intake, since SFA increase low-density lipoprotein cholesterol (LDL-c) levels, a known risk factor for cardiovascular disease (CVD). However, within LDL-c, small, dense LDL particles are more strongly related to CVD risk than large buoyant particles, and response to SFA vary for different foods. Dairy fat, when eaten as cheese, significantly lowers total cholesterol compared to butter. Here, we aimed to test the effect of the cheese matrix on lipoprotein particle size distribution response in overweight adults aged ≥ 50 years. Methods In this secondary analysis of a 6-week randomised parallel intervention(1); participants received ∼40g dairy fat in 1 of 4 treatments: (A) 120 g of full-fat cheddar cheese (FFCC); (B) reduced-fat cheese plus butter (RFC + B); (C) butter, calcium caseinate powder, and calcium supplement (CaCO3) (BCC); or (D) 120 g FFCC as per (A). Fasting EDTA blood samples at wk. 0 (baseline) and wk. 6 were analysed for lipoprotein particle size distribution via nuclear magnetic resonance (NMR) spectroscopy. To examine extremes in response, those with greatest reduction in LDL-c (n = 15, ‘positive’ responders) were compared to those with the greatest increase in LDL-c (n = 15, ‘negative’ responders). Results Correlation analyses between the change in cholesterol levels and change in particle size distribution suggest a relationship between change in LDL-c, HDL-c, and corresponding particle sizes, which differs dependent on the dairy fat matrix. The correlation of LDL-c and LDL particle (LDL-p) concentration weakened as less fat was present within a cheese matrix, as LDL-c decreased so did total LDL-p, due to larger LDL particles. The positive responders displayed a stronger relationship between change in cholesterol and lipoprotein levels, with the changes in cholesterol driven by the large LDL-p and large HDL-p. Conclusions Lipoprotein particle distribution is correlated with change in cholesterol levels after a 6-week intervention of dairy fat. The changes in LDL-c and HDL-c were driven by the less atherogenic, large LDL-p and large HDL-p which are inversely associated with CVD risk. The overall response in LDL-p to SFA appears to vary, dependent on the dairy food matrix in which the fat was eaten. Funding Sources Food for Health Ireland (FHI). Enterprise Ireland.

The cheese matrix: Understanding the impact of cheese structure on aspects of cardiovascular health – A food science and a human nutrition perspective

Health guidelines recommend limiting saturated fat consumption due to adverse associations with low‐density lipoprotein cholesterol, a marker for cardiovascular disease risk. Recently, this advice is being questioned, since it does not account for the diversity of fatty acids present in different foods and may be overly simplistic. Current research suggests that for dairy foods and cheese in particular, a matrix effect exists, whereby the other components present interact with the overall structure, leading to health benefits. This review examines how factors in cheese production and processing impact this matrix, and considers how they affect biological function, and the potential impact on human health.

Key aroma compounds identified in Cheddar cheese with different ripening times by aroma extract dilution analysis, odor activity value, aroma recombination, and omission

To determine the odor-active compounds in Cheddar cheeses with different ripening times (6, 10, and 14 mo), 39 potent odorants of Cheddar cheeses were identified with a flavor dilution factor range between 1 and 512 by aroma extract dilution analysis. To further determine their contribution to the overall aroma profile of Cheddar cheeses, odor activity values of 38 odorants with flavor dilution factors ≥1 were calculated. A Cheddar cheese matrix was developed to determine the concentrations and the odor thresholds of these key aroma compounds. The result of the aroma recombinant experiment prepared by mixing the key aroma compounds in the concentrations in which they occurred in Cheddar cheeses showed that the overall aroma profile of the recombinant sample was very similar to that of Cheddar cheese. The main different compounds in Cheddar cheese with different ripening time were acetic acid, butanoic acid, dimethyl trisulfide, methional, hexanal, (E)-2-nonenal, acetoin, 1-octen-3-one, δ-dodecalactone, furaneol, hexanoic acid, heptanal, and ethyl caproate. This study could provide important information for researching and developing Cheddar cheese-related products.

Microbiological, immunological, and histological changes in the gut of Salmonella Enteritidis-challenged rats fed goat cheese containing Lactobacillus rhamnosus EM1107

Cheeses are able to serve as suitable matrices for supplying probiotics to consumers, enabling appropriate conditions for bacteria to survive gastric transit and reach the gut, where they are assumed to promote beneficial processes. The present study aimed to evaluate the microbiological, immunological, and histological changes in the gut of Salmonella Enteritidis-challenged rats fed goat cheese supplemented with the probiotic strain Lactobacillus rhamnosus EM1107. Thirty male albino Wistar rats were randomly distributed into 5 experimental groups with 6 animals each: negative (NC) and positive (PtC) control groups, control goat cheese (CCh), goat cheese added with L. rhamnosus EM1107 (LrCh), and L. rhamnosus EM1107 only (EM1107). All animals, except NC group were challenged with Salmonella Enteritidis (109 cfu in 1 mL of saline through oral gavage). Microbial composition was assessed with high-throughput 16S rRNA sequencing by means of Illumina MiSeq (Illumina, San Diego, CA). Nuclear factor kappa B (NF-κB) from the animal cecum tissue was determined by real-time PCR and interleukins (TNF-α, IL-1β, IL-10, and IFN-γ) by means of ELISA. Myeloperoxidase and malondialdehyde levels were determined biochemically. The administration of the L. rhamnosus EM1107 probiotic strain, either as a pure culture or added to a cheese matrix, was able to reduce Salmonella colonization in the intestinal lumen and lessen tissue damage compared with rats from PtC group. In addition, the use of cheese for the probiotic strain delivery (LrCh) was associated with a marked shift in the gut microbiota composition toward the increase of beneficial organisms such as Blautia and Lactobacillus and a reduction in NF-κB expression. These findings support our hypothesis that cheeses might be explored as functional matrices for the efficacious delivery of probiotic strains to consumers.

Development of a functional whey cheese (ricotta) enriched in phytosterols: Evaluation of the suitability of whey cheese matrix and processing for phytosterols supplementation

This study aims to evaluate the suitability of whey cheese (ricotta) and whey cheese production process for phytosterols-enrichment. Therefore, the phytosterols stability of ricotta cheese was assessed during cheese processing (85 °C for 60 min) and storage (4 °C for 4 weeks). Given the novelty of the food matrix used, it was necessary to develop an innovative analytical method for sterols determination in enriched ricotta cheese. The developed HPLC-DAD method showed good linearity (R2 ≥ 0.9956) and reproducibility (0.4–7.6%), while extraction recoveries ranged between 83.7% and 84.6%. Phytosterols showed a good heat-stability in ricotta cheese matrix during cheese processing (87.0–89.7) %. Moreover, the functional cheese showed a homogeneous phytosterols distribution and maintained its potential bioactivity during its shelf-life since no significant variation of phytosterols levels was observed during storage (0.83 ± 0.03) g/100 g.

Evaluation of the Perceptual Interactions among Aldehydes in a Cheddar Cheese Matrix According to Odor Threshold and Aroma Intensity.

To evaluate the contributions of 3-methylbutanal, 2-methylbutanal, 2-methylpropanal, and benzaldehyde in cheddar cheese models, the threshold values, optimal concentration ranges, and perceptual actions of these compounds were determined at various concentrations. The thresholds for 3-methylbutanal, 2-methylbutanal, 2-methylpropanal, and benzaldehyde in the cheese matrix were 150.31, 175.39, 150.66, and 500.21 μg/kg, respectively, which were significantly higher than the corresponding values in water. The optimal concentration ranges of these aldehydes were determined as 150–300, 175–325, 150–350, and 500–1500 μg/kg, respectively. Based on the results of the threshold method and Feller’s model, five binary mixtures were found to have synergistic effects, and only the pair of 2-methylpropanal and benzaldehyde was determined to have a masking effect. In addition, the synergistic olfactory effects between the four ternary mixtures and the quaternary mixture of these aldehydes were also assesSsed using Feller’s model. In a σ-τ plot analysis, synergism was usually observed when these odor pairs were at their threshold levels. In summary, the results suggested that perceptual interactions among these aldehydes exist in a cheese model variably with different concentrations and threshold ratios. This study will be helpful to a further understanding of the nutty aroma and improving the aroma quality of cheddar cheese.

Linking oral processing behavior to bolus properties and dynamic sensory perception of processed cheeses with bell pepper pieces

The addition of food particles to food matrices is a convenient approach that allows to steer oral behavior, sensory perception and satiation. The aim of this study was to determine the influence of physical-chemical properties of heterogenous foods on oral processing behavior, bolus properties and dynamic sensory perception. Bell pepper gel pieces varying in fracture stress and concentration were added to processed cream cheese matrices differing in texture. Addition of bell pepper gel pieces to processed cheeses increased consumption time, decreased eating rate and led to harder and less adhesive bolus with more saliva incorporated. Addition of bell pepper gel pieces to processed cheeses decreased dominance rate and duration of creaminess, smoothness, melting and dairy flavor and increased graininess and bell pepper flavor. Increasing fracture stress of bell pepper gel pieces from 100 to 300 kPa resulted in longer consumption time and lower eating rate. For hard/non-adhesive processed cheese matrices increasing gel pieces fracture stress lead to a boli with larger particles and more saliva. These changes were accompanied by decreased dominance perception of creaminess and bell pepper flavor and increased dominance of graininess. Increasing the concentration of bell pepper gel pieces from 15 to 30% did not affect oral behavior but led to the formation of harder and less adhesive bolus with larger particles and less saliva that were perceived with reduced dominance of creaminess, meltiness and dairy flavor while dominance of graininess and bell pepper flavor increased. Changing the texture of the cheese matrix from soft/adhesive to hard/non-adhesive decreased consumption time, increased eating rate, did not influence bolus properties and decreased dominance rate of creaminess, smoothness and melting sensations. Number of chews and total consumption time were positively correlated with saliva content of the bolus, number of bolus particles, bolus hardness, dominance of firmness, chewiness and graininess. We conclude that the modification of physical-chemical properties of processed cheeses and embedded bell pepper gel pieces can be a strategy to steer oral behavior and bolus properties which consequently determine dynamic sensory perception.

Radio frequency reheating behavior in a heterogeneous food: A case study of pizza

Radio frequency (RF) energy could rapidly raise the material bulk temperature with deep power penetration and high energy efficiency. Although many studies on RF treatments have been carried out on different agricultural commodities or food, application of RF energy for studying heating behavior of heterogeneous food matrix is limited. Pizza is typically a heterogeneous food model with a base, cheese matrix and added toppings, and has been rarely evaluated for RF reheating. This study was aimed at using computer simulation for evaluating the RF reheating uniformity of a typical model pizza after baking based on measured thermal and dielectric properties (DPs) of its components (pizza base, cheese, salami and onion). The validation experiments were carried out up to a maximum reheating temperature of 85 °C in a 6 kW, 27.12 MHz RF system. The results showed that both dielectric constant and loss factor of pizza components increased with temperature, and at elevated temperatures, DP values for salami were the highest cheese, onion and pizza base. Both computer simulation and experiment provided similar temperature-time histories (with the maximum RMSE of 0.034 °C) in pizza base, cheese, salami and onion after RF reheating for 7.33 min. The fast RF reheating rate was observed in cooked salami both from the temperature-time history and predicted temperature distribution due to closed dielectric loss to constant value. The high sample temperature resulted in low moisture content. The RF heating uniformity could be improved by moving or rotating pizza and specially locating components in the further studies.

Effect of frozen and refrigerated storage on proteolysis and physicochemical properties of high-moisture citric mozzarella cheese

High-moisture mozzarella is one of the most-exported Italian cheeses worldwide, but its quality is affected by storage. Freezing is regarded as a solution to decrease product waste, extend market reach, and increase convenience, but its effect on quality has to be estimated. In this study, the details related to proteolysis, physicochemical properties, and sensory quality parameters of high-moisture mozzarella as a function of frozen storage (1, 3, and 4 mo) and subsequent refrigerated storage after thawing (1, 3, and 8 d) were evaluated. Frozen cheeses stored at -18°C showed a higher extent of proteolysis, as well as different colorimetric and sensory properties, compared with the fresh, nonfrozen control. Sensory evaluation showed the emergence of oxidized and bitter taste after 1 mo of frozen storage, which supports the proteolysis data. The extent of proteolysis of frozen-stored cheese after thawing was greater than that measured in fresh cheese during refrigerated storage. These results help better understand the changes occurring during frozen storage of high-moisture mozzarella cheese and evaluate possible means to decrease the effect of freezing on the cheese matrix.

Assessment of overall microbial community shift during Cheddar cheese production from raw milk to aging.

Cheese is a fermented dairy product that is made from animal milk and is considered to be a healthy food due to its available nutrients and potential probiotic characteristics. Since the microbes in the cheese matrix directly contribute to the quality and physicochemical properties of cheese, it is important to understand the microbial properties of cheese. In this study, Cheddar cheeses produced on three different dates at the Arbuthnot Dairy Center at Oregon State University were collected to determine the microbial community structure. A total of 773,821 sequencing reads and 271 amplicon sequence variants (ASVs) were acquired from 108 samples. Streptococcus and Lactococcus were observed as the most abundant ASVs in the cheese, which were used as the starter lactic acid bacteria (SLAB). Escherichia coli was detected in the raw milk; however, it was not detected after inoculating with SLAB. According to an alpha diversity analysis, SLAB inoculation decreased the microbial richness by inhibiting the growth of other bacteria present in the milk. A beta diversity analysis showed that microbial communities before the addition of SLAB clustered together, as did the samples from cheese making and aging. Non-starter lactic acid bacteria (NSLAB) were detected 15 weeks into aging for the June 6th and June 26th produced cheeses, and 17 weeks into aging for the cheese produced on April 26th. These NSLAB were identified as an unidentified group of Lactobacillaceae. This study characterizes the changes in the Cheddar cheese microbiome over the course of production from raw milk to a 6-month-aged final product. KEY POINTS: • 271 ASVs were acquired from cheese production from raw milk to 6-month aging. • Addition of SLAB changed the microbial diversity during Cheddar cheese making procedure. • NSLAB were detected more than 15 weeks after aging. Graphical Abstract.

Effect of Lactococcus lactis expressing phage endolysin on the late blowing defect of cheese caused by Clostridium tyrobutyricum

Clostridium tyrobutyricum has been identified as a major species associated with the late blowing defect (LBD) of semi-hard and hard cheeses, due to undesirable butyric acid fermentation. To find new strategies to control this spoilage bacterium, we investigated the delivery of a bacteriophage endolysin by a cheese starter culture. The nisin producer Lactococcus lactis subsp. lactis INIA 415 was engineered to produce the CTP1L endolysin, encoded by the virulent bacteriophage ΦCTP1 of C. tyrobutyricum and with a demonstrated lytic activity in vitro, to the cheese matrix. The presence of the nisRK two-component regulatory system in the host strain allowed constitutive expression of the endolysin under the control of the nisA promoter (PnisA), while the use of a signal peptide (SLPmod) led to successful secretion of the active endolysin to the surrounding media. Engineered lysins with a second cell wall binding domain were also tested and shown to have improved lytic activity. Transformation of L. lactis subsp. lactis INIA 415 with endolysin delivery plasmids had a detrimental effect on its ability to produce nisin in milk, but did not affect its acidifying capacity. Transformed L. lactis subsp. lactis INIA 415 were evaluated as starters in cheeses contaminated with spores of C. tyrobutyricum. Evolution of microbiological parameters, pH and dry matter of cheeses were studied, and Clostridium metabolism and LBD in cheeses were monitored by sensory and instrumental analyses during ripening. Cheese made with the parental strain L. lactis subsp. lactis INIA 415 delayed LBD by one month, attributable to the activity of the nisin, but it was not sufficient to arrest the growth of C. tyrobutyricum during ripening completely. The use of the endolysin-producing strains in cheese manufacture as single cultures also delayed the appearance of LBD by one month, attributable to the activity of the endolysin produced in situ during ripening, because nisin activity in these cheeses was very low at day 1 and undetectable from 15 days onwards. Endolysin was more effective than nisin in inhibiting Clostridium growth, since cheeses made with the CTP1L or the chimeric derivative producers only as starters showed lower LBD symptoms, higher lactic acid levels and lower concentrations of propionic and butyric acids (associated with off-flavours) than cheese made with the parental strain. Investigation of different promoters to maximise endolysin production may help to implement CTP1L as a tool to control C. tyrobutyricum by L. lactis cheese starter and reduce LBD even further.

Active Whey Protein Edible Films and Coatings Incorporating Lactobacillus buchneri for Penicillium nordicum Control in Cheese

Fungal contamination of food is responsible for health issues and food waste. In this work, the incorporation of a lactic acid bacteria (LAB) with antifungal properties (Lactobacillus buchneri UTAD104) into whey protein-based films and coatings was tested for the control of an ochratoxigenic fungi (Penicillium nordicum) in a cheese matrix. The incorporation of L. buchneri cells resulted in thicker films with less luminosity than control films and colour alteration. Nevertheless, cells inclusion did not alter moisture content, water vapour permeability, mechanical properties, hydrophobicity and chemical structure of the films. Whey protein films were able to maintain the viability of L. buchneri UTAD104 cells in 105 CFU/mL after 30 days of storage at 25 °C. When applied in cheese, films and coatings containing L. buchneri cells prevented fungal contamination for at least 30 days, while control cheeses with films and coatings either without LAB or with Lactobacillus casei UM3 (a strain without antifungal ability) showed fungal contamination during that period. Ochratoxin A was not found in cheeses treated with films and coatings containing L. buchneri UTAD104. Results showed that the inclusion of a LAB with antifungal properties in edible films and coatings can help to reduce or eliminate P. nordicum contamination in cheeses.

Phage-based forensic tool for spatial visualization of bacterial contaminants in cheese

Traditional procedures for microbial testing typically involve a homogenizing step. These methods give valuable information on the presence or enumeration of a bacterial contaminant, but not where the contaminant was in the original sample. Spatial information could be useful in troubleshooting sources of bacterial contamination in a processing plant. For example, if the contaminant was localized on the top of a food such as cheese, this might indicate dripping condensate along a specific processing line as its source. The objective of this proof-of-concept study was to evaluate the use of a genetically engineered phage to detect bacterial contaminants on cheese to be able to visualize the contaminants without the use of magnification. In this study, a T7 bacteriophage engineered to overexpress the luciferase NanoLuc (Promega, Madison, WI) was utilized to reveal the spatial location of Escherichia coli on lysogeny broth (LB) agar and queso fresco (QF). Four scenarios were tested to explore how phage may be applied, with a blue bioluminescent signal revealing the spatial location of contaminants: (1) phage applied topically via molten soft agar to E. coli-inoculated (a) LB agar or (b) QF; and (2) phage incorporated within (a) LB agar or (b) QF and then inoculated with E. coli. Each was tested in triplicate. Cultures of E. coli BL21 grown for 18 h were serially diluted in phosphate-buffered saline and inoculated onto 8 ± 0.5 g of LB agar or QF in 6-well plates. Plates were incubated at 37°C for 8 h for condition 1a, 24 h for 1b and 2b, and 22 h for 2a. For 1a and 1b, stock phage was added to molten soft agar, applied topically, and incubated for 2 additional hours to allow for E. coli infection. After incubation, the substrate NanoGlo (Promega) was added to cover the surface of the agar or cheese and imaged immediately in a dark box using a digital camera and long exposure to capture the bioluminescent signal. Photographs captured small blue spots where the incubated colony-forming units were located. The lowest inoculum level of E. coli detected for each scenario was 1.43 × 101 ± 9.94, 1.18 × 101 ± 7.07, 5.48 × 101 ± 1.19 × 101, and 2.37 × 101 ± 1.40 × 101 cfu/well, for 1a, 1b, 2a, and 2b, respectively. These data demonstrate that the reporter phage proof-of-concept could be used as a forensic tool to visualize the spatial location of bacteria in a cheese matrix. Future work will translate this concept to dairy-relevant phage-pathogen systems.

Volatile Flavor Compounds in Cheese as Affected by Ruminant Diet.

Extensive research has been conducted concerning the determination and characterization of volatile compounds contributing to aroma and flavor in cheese. Considerable knowledge has been accumulated on the understanding of the mechanisms through which these compounds are formed during ripening, as well as on the optimization of the methodological approaches which lead to their detection. More recently, particular attention has been given to the aromatic properties of milk and cheeses obtained from lactating dairy ruminants fed experimental diets, characterized, for instance, by the addition of trace elements, natural supplements, or agricultural by-products rich in bioactive compounds. The purpose of this review is to summarize the major families of volatile compounds most commonly found in these types of dairy products at various ripening stages, describing in greater detail the role of animal diet in influencing the synthesis mechanisms most commonly responsible for cheese flavor determination. A large number of volatile compounds, including carboxylic acids, lactones, ketones, alcohols, and aldehydes, can be detected in cheese. The relative percentage of each compound depends on the biochemical processes that occur during ripening, and these are mainly mediated by endogenous enzymes and factors of bacterial origin whose function can be strongly influenced by the bioactive compounds taken by animals with the diet and released in milk through the mammary gland. Further evaluations on the interactions between volatile compounds and cheese matrix would be necessary in order to improve the knowledge on the synthesis mechanisms of such compounds; in addition to this, more should be done with respect to the determination of synergistic effects of flavor compounds, correlating such compounds to the aroma of dairy products.

Application of vacuum solid-phase microextraction for the analysis of semi-hard cheese volatiles

Solid-phase microextraction (SPME) is a well-established technique in the analysis of food volatile compounds, usually performed for qualitative analysis. This paper presents an elaboration of conditions for SPME analysis of main volatile compounds in hard cheese and an evaluation of suitability of vacuum to improve the transfer of volatile compounds towards SPME fiber. Compounds representing the main groups of hard cheese volatiles were investigated: 1-pentanol, butanoic acid, 2,3-butanedione and 2-heptanone. Parameters for SPME extraction (temperature, water, sodium carbonate addition, time, vacuum) were evaluated. Application of vacuum had a positive effect on all analytes when extraction was performed from water, but in the cheese matrix the effect was significant only for butanoic acid. Extraction time was the most significant factor for extraction efficiency in examined cheeses, while temperature had a minor effect on the amount of extracted volatiles. The method was applied on Edam, Emmentaler, Gouda and Maasdam cheeses obtained from the market.

Dynamic in situ imaging of semi-hard cheese microstructure under large-strain tensile deformation: Understanding structure-fracture relationships

Changes in the microstructure of semi-hard cheeses were observed in situ under tensile deformation by placing a microtensile stage directly under a confocal scanning laser microscope, and recording force/displacement data simultaneously. On tensile deformation, detachment of fat globules and their subsequent release from the cheese matrix were observed, suggesting that they are weakly bonded to or entrapped within the cheese matrix. Moreover, an inherent micro-defect was observed at a curd granule junction within the cheese matrix, which fractured along the curd granule junction under tensile deformation, suggesting that such micro-defects could be a key to the formation of undesirable slits or cracks. Furthermore, the fracture behaviour of semi-hard cheese varied with ripening temperature, coagulant type, and inhibition of residual chymosin activity. Overall, this study demonstrated the potential of dynamic in situ imaging of cheese microstructure for developing a greater understanding of the breakdown behaviour of cheese matrices.

Development and Characterization of Probiotic Buffalo Milk Ricotta Cheese

In the current study, probiotic L. acidophilus La-05 cell pellets were incorporated into buffalo milk Ricotta matrix. The compositional, colour, textural and sensorial parameters of control and probiotic Ricotta cheese were statistically non-significant (P < 0.05). The respective moisture, fat, protein, lactose and ash content of PRC was 75%, 6.41%, 11.88%, 4.88% and 1.86% with L. acidophilus La-05 count 7.8 ± 0.2 log CFU/g of product. The L*, a* and b* values of PRC were 81.48, −1.70 and 9.55, respectively. Scanning electron microscopy revealed that Ricotta cheese matrix mainly consists of protein network, the particles of coagulated whey proteins were inter-connected, and casein appeared as small clusters. The probiotic organism was embedded into protein matrix, which may provide an added protection to organisms. Descriptive sensory analysis characterized PRC as white, shiny, consistent in terms of color and uniform in terms of appearance with a flat flavour. Overall, the product got high overall acceptability (9.0 out of 10 scales) scores. The principal component analysis revealed four principal components of 18 sensory data explaining 92.433% of the total variance of study.

Simulated oral processing, in vitro digestibility and sensory perception of low fat Cheddar cheese containing sodium alginate

Investigation on the effect of fat and fat replacer sodium alginate (alginate) on low fat Cheddar cheese was conducted by systematic studies in three cheese types, namely control full fat cheese (CFFC ~ 32% fat), control low fat cheese (CLF C ~ 5% fat) and low-fat cheese with alginate (LFCA ~ 3% fat). Lubrication properties, coefficient of friction, in vitro digestibility, and textural sensory analysis were studied. Coefficient of friction (CoFmin) of CFFC and LFCA were not different (P > 0.05) from each other and were lower (P < 0.05) than CLFC. Rate of protein release and cheese matrix disintegration were directly influenced by cheese composition (moisture and fat content and presence of alginate) and textural properties of cheese. Hence, this study suggested that the presence of fat and sodium alginate in cheese exhibited more lubrication and enhanced digestion compared to CLFC, whereas sensory properties of all cheeses were similar to each other.

Environmental conditions and serotype affect Listeria monocytogenes susceptibility to phage treatment in a laboratory cheese model

Listeria monocytogenes can survive and grow in a variety of environments, including refrigeration, making it difficult to control and highlighting the importance of optimizing control strategies against this pathogen. Listeria phages are attractive biocontrol agents because phages bind to specific wall teichoic acids (WTA) on the bacterial cell wall, inhibiting pathogens without disrupting the normal microbiota or structure of the food. Common stresses found on dairy products can affect cell wall composition and structure and subsequently affect the efficiency of control strategies that target the cell wall. The goal of this study was to determine the effect of a range of pH and temperatures on the effectiveness of a commercial phage cocktail treatment against several strains of L. monocytogenes in a cheese matrix. We developed a laboratory-scale cheese model that was made at different pH, treated with phage, and then inoculated with L. monocytogenes. Cheeses were incubated at 6, 14, or 22°C for 14 d, and bacterial counts were determined on d 1, 7, and 14. Our data show that phage treatment has a limited ability to reduce L. monocytogenes counts at each temperature tested; however, it was more effective on specific strains of L. monocytogenes when cheese was stored at higher temperatures. More specifically, the average counts of L. monocytogenes on phage-treated cheese stored at 22°C were significantly lower than those on phage-treated cheese stored at 6 or 14°C. Similarly, phage treatment was significantly more effective at inhibiting L. monocytogenes on cheese made at higher pH (6 and 6.5) compared with counts on cheese made at pH 5.5, where L. monocytogenes did not grow. Furthermore, serotype was found to affect the susceptibility of L. monocytogenes to phage treatment; serotype 1/2 strains showed significantly higher susceptibility to phage treatment than serotype 4b strains. Overall, our results suggest the importance of considering the efficacy of phage under conditions (i.e., temperature and pH) specific to a given food matrix when applying interventions against this important foodborne pathogen.