The effect of using an exopolysaccharide‐producing culture on the physicochemical properties of low‐fat and reduced‐fat Kasar cheeses

A mixed starter culture containing exopolysaccharide (EPS)‐producing strains of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was combined with Lactobacillus helveticus LH301 and used in the manufacture of low‐fat and reduced‐fat Kasar cheeses. For comparison, low‐fat (C10) and reduced‐fat (C20) cheeses were made using EPS‐producing (EPS⁺) starter strain and EPS‐non‐producing (EPS^?) starter strain. The physicochemical properties of the cheeses were assessed in terms of chemical composition, texture, microstructure and microbial content over 90 days. Cheeses made with EPS‐producing culture (EPS10 and EPS20) had lower protein contents than control cheeses with 10% and 20% fat in dry basis (C10 and C20). Scanning electron microscopy images showed that using EPS‐producing culture resulted in a less compact protein matrix and sponge‐like structure in the cheese samples. In general, cheeses made using EPS‐producing culture had lower total viable counts. This could be related to the reduced survivability of EPS‐producing cells in the cheese matrix during ripening due to autolysis ability.     

Characterization of autochthonal yeasts isolated from Spanish soft raw ewe milk protected designation of origin cheeses for technological application

The yeasts involved in the ripening process of artisanal soft raw ewe milk Protected Designation of Origin (PDO) Torta del Casar and Queso de la Serena cheeses produced in Extremadura, Spain, were isolated throughout their ripening process, strain typed, and characterized for some important technological properties. A total of 508 yeast isolates were obtained and identified by inter-single sequence repeat anchored PCR amplification analysis and subsequent sequencing of the internal transcribed spacer ITS1/ITS2 5.8S rRNA. A total of 19 yeast species representing 8 genera were identified. Debaryomyces hansenii, Pichia kudriavzevii, Kluyveromyces lactis, and Yarrowia lipolytica were the predominant species. We selected 157 isolates, by genotyping and origin, for technological characterization. The evaluation of yeast isolates' growth under stress conditions of cheese ripening showed that 87 presented better performance. Among them, 71 isolates were not able to catabolize tyrosine to produce a brown pigment. Principal component analysis of the biochemical features of these isolates showed that 9 strains stood out, 3 K. lactis strains (2287, 2725, and 1507), 2 Pichia jadinii (1731 and 433), 2 Yarrowia alimentaria (1204 and 2150), Y. lipolytica 2495 and P. kudriavzevii 373. These strains displayed strong extracellular proteolytic activity on skim milk agar as well as an adequate enzymatic profile (strong aminopeptidase and weak protease activity), suggesting their great potential for cheese proteolysis. Extracellular lipolytic activity was mainly restricted to Yarrowia spp. isolates and weakly present in P. kudriavzevii 373 and K. lactis 2725, although enzymatic characterization by API-ZYM (bioMérieux SA) evidenced that all may contribute, at least in part, to the lipolysis process. Moreover, these strains were able to assimilate lactose, galactose, and glucose at NaCl concentrations higher than that usually found in cheese. However, lactate and citrate assimilation were limited to Y. lipolytica 2495, P. kudriavzevii 373, and P. jadinii 433, and may contribute to the alkalinizing process relevant to biochemical processes that take place in the last stages of ripening. By contrast, K. lactis strains showed acidifying capacity and β-galactosidase activity and may take part in the initial stages of ripening, together with lactic acid bacteria. Thus, considering the technological characteristics studied, the 9 selected strains presented biochemical features well suited to their potential use as adjunct cultures, alone or in combination with autochthonous starter bacteria in the cheesemaking process, to overcome the heterogeneity of these PDO cheeses, preserving their unique sensory characteristics.     

Two strains of nonstarter lactobacilli increased the production of flavor compounds in soft cheeses

The contribution to flavor generation and secondary proteolysis of 2 strains of mesophilic lactobacilli isolated from cheese was studied. Miniature soft cheeses (200 g) were produced with or without the inclusion of a culture of Lactobacillus plantarum I91 or Lactobacillus casei I90 in the starter composed of Streptococcus thermophilus. During ripening, cheeses containing the added lactobacilli showed an increased content of total free amino acids, but this increase was only significant in cheeses with Lb. plantarum I91. In addition, free amino acid profiles were modified by selective increases of some amino acids, such as Asp, Ser, Arg, Leu, and Phe. Cheeses inoculated with Lb. plantarum I91 or Lb. casei I90 were also characterized by a significantly higher concentration of diacetyl, a key flavor compound, and an increased content of acetoin. Results suggest an increase in the catabolism of either citrate or aspartate, with the production of the derived aroma compounds. Overall, aspartate content increased in both lactobacilli-added cheeses, whereas citrate was more or less constant, suggesting that aspartate could be the source of increased diacetyl and acetoin. A triangle aroma test showed that the addition of the lactobacilli strains significantly changed the sensory attributes of cheeses. At least 11 of 12 panelists commented that the aroma of cheeses with adjuncts was more buttery than that of control cheeses, which is desirable in most soft cheeses. Both Lb. plantarum I91 and Lb. casei I90 performed well as adjunct cultures by influencing cheese aroma development and cheese proteolysis.     

Comparison of the volatile profiles of Arzúa-Ulloa and Tetilla cheeses manufactured from raw and pasteurized milk

Levels of volatile compounds in Arzúa-Ulloa and Tetilla cheeses manufactured from raw and pasteurized milk were investigated. Analysis of volatile compounds in six raw milk (RM) starter-free cheeses (15–45 days old) and six pasteurized milk (PM) cheeses made with deliberately added starters (15–45 days old) manufactured in different dairies, was performed on an automatic dynamic headspace apparatus coupled to a GC/MS. The volatile fraction of RM cheeses displayed 46 volatile compounds (34 for PM cheeses) including fatty acids, esters, aldehydes, alcohols, ketones, hydrocarbons and sulphur compounds. Fatty acids and several esters were only detected in RM cheeses. Moreover, the highest contents of methylketones, secondary alcohols and branched-chain aldehydes and alcohols were also observed in RM cheeses. All results confirm more intense lipolysis in RM cheeses than in PM cheeses. In addition, branched-chain aldehydes and alcohols were significantly more abundant in RM than in PM cheeses, which indicates that catabolism of branched-chain amino acids was significantly higher in RM cheeses. This study has provided useful information which will allow the selection of starter and non-starter bacteria more suitable for manufacturing Arzúa-Ulloa and Tetilla pasteurized milk cheeses with organoleptic characteristics similar to those of traditional raw milk cheeses.     

Effect of spray‐drying parameters on the solubility and the bulk density of camel milk powder: A response surface methodology approach

Response surface methodology coupled with a Box–Behnken experimental design was used to investigate the effect of the air inlet drying temperature, the feed rate, and the fat content on the solubility and the bulk density of spray‐dried camel and cow milk powders. The response surface methodology analysis highlighted that milk fat content and feed rate were the most effective parameters affecting the solubility and the bulk density of cow and camel milk powders. Importantly, there was no significant interaction between the studied drying parameters and camel milk powder solubility or bulk density. Overall, camel milk powder exhibited a comparable solubility to that of cow milk powder with a higher bulk density.     

Development of reduced‐fat cheeses with the addition of Agave fructans

Cheeses containing Agave fructans were compared with both full‐fat and reduced‐fat samples without fructans. Microstructure results showed that the cheeses obtained were very similar to the control samples (without fructans), even the full‐fat control sample, demonstrating the texturing role of the carbohydrates. Regarding the composition, a moisture content of 47.96 ± 1.45 and a good protein retention with a low‐fat content were found. Therefore, the cheese yield was not adversely affected, and no significant differences were observed in sensory aspects. Considering the health benefits of fructans and their abundance, this development could represent an innovation for dairy industry.     

Isolation and characterisation of lactic acid bacteria strains from raw camel milk for potential use in the production of fermented Tunisian dairy products

The aim of this work was to study the suitability of camel milk for the production of dairy products by lactic acid fermentation. Sixty strains of lactic acid bacteria (LAB) were isolated from camel milk. The strains were tested for their acidification activity, ability to use citrate, exopolysaccharide production, lipolytic, proteolytic activities and resistance to antibiotics. Ten strains were investigated for their ability to metabolize carbohydrates and that resulted in the identification of 5 Lactococcus lactis, 1 Lactobacillus pentosus, 2 Lactobacillus plantarum, 1 Lactobacillus brevis and 1 Pediococcus pentosaceus strains. Two strains of Lactococcus lactis SCC133 and SLch14 were selected to produce traditional Tunisian fermented dairy products (Lben, Raib, Jben cheese and Smen). These strains were chosen based on their acid production capacity and their ability to produce a high yield of biomass.     

Viability of the Lactobacillus rhamnosus HN001 Probiotic Strain in Swiss‐ and Dutch‐Type Cheese and Cheese‐Like Products

The objective of this study was to determine the viability of the probiotic Lactobacillus rhamnosus HN001 in Swiss‐type and Dutch‐type cheese and cheese‐like products (milk fat is substituted by stearin fraction of palm fat) during manufacture, ripening, and storage. The use of the probiotic L. rhamnosus HN001 in Dutch‐type cheese and cheese‐like products significantly (P = 0.1) changed their chemical composition (protein and fat content) and an insignificant increase (approximately 1.6% in cheese‐like products and approximately 0.3% in cheese) in yield. L. rhamnosus HN001 did not affect the rate of changes in the pH of ripened cheese and cheese‐like products. A minor increase in probiotic counts was observed in initial stages of production and were partially removed with whey. Ripened cheese and cheese‐like products were characterized by high survival rates of probiotic bacteria which exceeded 8 log CFU/g after ripening. An insignificant reduction in the number of viable probiotic cells was noted during storage of Swiss‐type and Dutch‐type cheese, whereas a significant increase in probiotic cell counts was observed in cheese‐like products during storage.     

A survey of non-starter lactic acid bacteria in traditional cheeses: Culture dependent identification and survival to simulated gastrointestinal transit

Cultivable NSLAB in traditional Pasta filata and ewes' milk cheeses were studied by both PCR-DGGE of cells from Rogosa agar and by isolation and molecular identification after a simulated gastric juice (SGJ) treatment of the cheese. Two to six species were retrieved from each sample. The majority of isolates were identified as Lactobacillus paracasei, Lactobacillus fermentum, Lactobacillus rhamnosus, Enterococcus or Pediococcus. Bile tolerance and bile salt hydrolase (BSH) activity were tested on 88 strains: 64% were able to grow with ≥0.15% bile and 40% were BSH positive. The effect of simulated digestion was tested on 15 strains. Inactivation ranged from 0.15 to 2.93 log cycles; most of the lethality was associated with pancreatic juice treatment. Although SGJ treatment alone may not provide a correct estimate of tolerance to gastrointestinal transit, it allowed selection of strains with a high tolerance to gastric juice, which may be tested as probiotic candidates.     

The effect of adding enzyme‐modified cheese on sensory and texture properties of low‐ and high‐fat cream cheeses

The influence of enzyme‐modified cheese (EMC) and fat content on sensory and texture properties of cream cheese was investigated. Enzyme‐modified cheese and fat content were set at three levels each, and organoleptic and texture properties for all experimental cheeses were then determined. Data were analysed using response surface methodology. Both design parameters had significant influence on sensory and texture properties. The EMC did not alter hardness significantly, whereas the higher fat formula had the higher hardness. The results indicated that the optimum level of EMC was less than 1% for high‐fat cream cheeses and at least 5% for low‐fat cream cheeses.     

Light‐induced protein and lipid oxidation in low‐fat cheeses: Effect on degree of enzymatic hydrolysis

The effect of proteolysis on oxidation in low‐fat cheese was investigated. The accumulation of dityrosine during storage increased significantly in the cheese with a high degree of proteolysis, while hexanal and heptanal were lower in the cheese with high proteolytic activity, indicating that the peptides/free amino acids acted as antioxidants on the propagating step in lipid oxidation. Dimethyl disulphide concentration was also lower in the cheese with a higher level of peptides. Therefore, oxidation of tyrosine residues seemed to function as antioxidants both regarding secondary lipid oxidation products and protein‐derived oxidation products through formation of dityrosine, being a termination reaction.     

Anti‐inflammatory and anticancer activities of water‐soluble peptide extracts of buffalo and cow milk Cheddar cheeses

This article aimed to assess the anti‐inflammatory and anticancer potential of water‐soluble peptide (WSP) extracts from buffalo and cow milk Cheddar cheeses. Anti‐inflammatory activity was evaluated on the basis of nitric oxide (NO) production in lipopolysaccharide‐stimulated macrophage (RAW‐264.7) cells. A cell viability assay, cell cycle arrest and apoptosis were performed to explore anticancer activity in a colon cancer model (HT‐29). The WSP extracts of both Cheddar cheeses effectively inhibited NO production in activated macrophages. Maximum growth inhibition was observed in the HT‐29 cells at concentrations of 400 and 500 μg/mL. A significant increase in cell population at G₀/G₁ phase of the cell cycle was observed. Moreover, the WSP extracts also induced extensive apoptosis in colon cancer cells.     

Microbiological and physicochemical properties of dry‐cured neck inoculated with probiotic of Bifidobacterium animalis ssp. lactis BB‐12

The effect of inoculum level of Bifidobacterium animalis ssp. lactis BB‐12 probiotic strain and ripening period on the quality of dry‐cured neck was studied. The microbiological parameters (Enterobacteriaceae, LAB and TVC) and physicochemical attributes (pH value, a_w, TBARS index, colour) were determined directly after fermentation at 15 °C for 3 weeks, after 6 and 12 months of ripening at 4 °C. The highest LAB count and a lower pH value were found in the meat inoculated with probiotic strain at 6.6 log cfu g^?1 (B2) followed by inoculation with probiotic strain at 6.3 log cfu g^?1 (B1). Level of inoculation had not had an influence on water activity, TBARS index and total colour parameters. Changes of fat oxidation during half‐year of ripening were limited in probiotic meat samples compared to naturally fermented control meat (C). Based on the results, it can be concluded that the most favourable physicochemical and microbiological parameters of the dry‐cured neck were obtained after 6 months of ripening. At that time, the Bifidobacterium BB‐12 at both levels is a good potential starter for meat fermentation.     

Effect of digestive enzymes on the activity of camel‐milk insulin

This study investigated the effect of digestive enzymes on the activity of camel‐milk insulin. The digestion was performed using the sequential action of pepsin and pancreatin. Proteolysis degree was estimated using the O‐phthaldialdehyde method. Insulin concentration was determined using an enzyme‐linked immunosorbent assay (ELISA). Results revealed that milk proteins were partially digested by pepsin alone and the degradation was increased during the pepsin–pancreatin digestion as compared to control. Insulin lost its activity after 30 min of pepsin digestion, and it was not detected by ELISA. This study strongly suggests that insulin is not responsible for the antidiabetic action of camel's milk.     

Angiotensin converting enzyme‐inhibitory activity and antimicrobial effect of fermented camel milk (Camelus dromedarius)

This study aimed to determine the angiotensin converting enzyme‐inhibitory activity and antimicrobial effect of fermented camel milk. Samples were prepared either using Lactobacillus acidophilus and Streptococcus thermophilus or Lactobacillus helveticus and Str. thermophilus and labelled as S1 and S2, respectively. The IC₅₀ values of S1 and S2 samples ranged between 113–200 and 70–133 μg/mL, respectively. The antimicrobial effects of S1 and S2 samples against Bacillus cereus, Salmonella Typhimurium and Staphylococcus aureus were apparent after 12 h of incubation and continued until 15 days of storage, whereas unfermented camel milk exhibited no antimicrobial effects against any of the tested pathogens.     

Proteolysis,protein oxidation and protease activity in dry‐cured Xuanwei ham during the salting stages

Twenty‐four experimental dry‐cured Xuanwei hams were salted using a standard method for 90 days. The proteolysis, protein oxidation and protease activities in biceps femoris (BF) and semimembranoesus (SM) muscles of dry‐cured Xuanwei ham were investigated during the salting phase. At the end of salting, the salt content increased to 35.2 g kg^?1 muscle in BF and 54.2 g kg^?1 muscle in SM. During the salting stage, salt soluble proteins were degraded mainly into water soluble proteins that were further broken down to peptides with molecular weights mostly greater than 1 kDa. Although large amounts of smaller peptides and free amino acids were generated, especially when the hams were aged. The carbonyl contents were increased but lower than 1.57 nmol mg^?1 proteins in muscles during the salting stage. The cathepsin B, dipeptidyl peptidase I (DPP I), alanyl (AAP), arginyl (RAP) and leucyl (LAP) aminopeptidase all remained active while salt content strongly inhibited cathepsin L and DPP IV in the first 90 days. The results suggested that the salting process promoted the hydrolysis of proteins, and increased the muscle protein oxidation at a slower rate.     

Angiotensin‐converting enzyme‐inhibitory and antithrombotic activities of soluble peptide extracts from buffalo and cow milk Cheddar cheeses

The aim of the study was to evaluate potential role of a water‐soluble peptide (WSP) extracts derived from buffalo and cow milk Cheddar cheeses with special reference to their antihypertension and antithrombotic activities. The WSP fractions collected at different stages of ripening were tested to assess their degree of proteolysis, their peptides were profiled by RP‐HPLC and in vitro assays for potential bioactivity were conducted. The peptide peak development was observed with slight differences in peaks number, area and height. Both angiotensin‐converting enzyme‐inhibitory and antithrombotic activities increased progressively during ripening. In comparison, the highest activities were observed in peptide extracts obtained from buffalo milk Cheddar cheese, in a dose‐dependent fashion.