Cheese Treatments Research Articles

Assessing the yield, microstructure, and texture properties of miniature Chihuahua-type cheese manufactured with a phospholipase A1 and exopolysaccharide-producing bacteria

Chihuahua cheese or Mennonite cheese is one of the most popular and consumed cheeses in Mexico and by the Hispanic community in the United States. According to local producers the yield of Chihuahua cheese ranges from 9 to 9.5kg of cheese from 100kg of milk. Cheese yield is a crucial determinant of profitability in cheese-manufacturing plants; therefore, different methods have been developed to increase it. In this work, a miniature Chihuahua-type cheese model was used to assess the effect of a phospholipase A1 (PL-A1) and exopolysaccharide (EPS)-producing bacteria (separately and in combination) on the yield, microstructure, and texture of cheese. Four different cheeses were manufactured: cheese made with PL-A1, cheese made with EPS-producing bacteria, cheese with both PL-A1 and EPS-producing bacteria, and a cheese control without PL-A1 or EPS-producing bacteria. The compositional analysis of cheese was carried out using methods of AOAC International (Washington, DC). The actual yield and moisture-adjusted yield were calculated for all cheese treatments. Texture profile analyses of cheeses were performed using a texture analyzer. Micrographs were obtained by electron scanning microscopy. Fifty panelists carried out sensorial analysis using ranking tests. Incorporation of EPS-producing bacteria in the manufacture of cheese increased the moisture content and water activity. In contrast, the addition of PL-A1 did not increase fat retention or cheese yield. The use of EPS alone improved the cheese yield by increasing water and fat retention, but also caused a negative effect on the texture and flavor of Chihuahua cheese. The use of EPS-producing bacteria in combination with PL-A1 improved the cheese yield and increased the moisture and fat content. The cheeses with the best flavor and texture were those manufactured with PL-A1 and the cheeses manufactured with the combination of PL-A1 and EPS-producing culture.

Evaluation of the Influence of Various Biodegradable Packaging Materials on the Quality and Shelf Life of Different Food Products

Abstract The aim of the present research was to summarize the results of investigations carried out on the influence of different biodegradable polymer packaging materials on the shelf life and quality of several food products during storage. In Latvia, most of consumers consider that polymers as a material for food packaging are overly used, and they support the idea of introducing new eco-friendly food packaging. Biodegradable films were investigated for their ability to extend the shelf life of apple salad and minimally processed shredded carrots stored at 4 °C. It was found that they can guaranty the same as or even a longer shelf life than that provided by conventional polymer films. Bio PLA transparent films, thermoformed PLA containers, and cellulose-based films were tested for fresh produce packaging. Ceramis®-PLA-SiOx barrier coated films were tested for their influence on the quality of food products - rye bread, apple-black currant marmalade candies, and soft cheese Kleo - during storage. PLA and PHB films showed satisfactory results for packaging of perishable foods - salad with meat in mayonnaise. Ceramis®-PLA-SiOx films were used for vacuum packaging and also for mild thermal treatment (Sous vide) of soft cheese, providing its prolonged shelf life. Some BoPLA films specially envisaged for packaging of confectionery were tested for milk pomade sweet - sherbet - packaging. Its quality was evaluated mainly by moisture content and by changes in hardness during storage. The results suggest that biodegradable packaging materials can be a successful alternative to the conventional polymers for packaging of several food products, which could provide an essential contribution in reducing the environmental pollution.

IMPROVEMENT OF WHITE CHEESE SPREAD PROPERTIES: 1. COMPARATIVE STUDY

The aim of this study was to develop properties of white cheese spread by using various ingredients. Seven treatments of cheese were manufactured from different ratios of quark, Ras, Cheddar, precooked cheeses, skim milk powder, whey powder, palm and butter oils and emulsifiers. Resultant cheese was stored for 8 weeks at 5 or for 4 weeks at 25°C. Increasing amount of Ras and Cheddar cheese added to the blend of processed cheese spread decreased the pH values while increased water soluble nitrogen of the resultant cheese. Total solids, fat, total nitrogen and total volatile fatty acids values of cheese raised by increasing proteins and oils in the blends. Heating of cheese blends at 85°C for 15 min. decreased total viable bacterial count and mould and yeast numbers. From the sensory evaluation, the treatment which gained the highest scores contained quark 30%, Ras cheese 5%, precooked cheese 5%, Cheddar cheese 4%, palm oil 15%, butter oil 3%, skim milk powder 2%, whey powder 3%, emulsifying salts 3% and water 30%.

High-pressure treatment applied throughout ripening of a goat cheese caused minimal changes on free fatty acids content and oxidation in mature cheese

High pressure (HP) has rapidly been gaining in importance for the food processing sector due to recent technological developments and increasing consumer demand for minimally processed and healthy foods. However, it is necessary to study the effect of HP on quality parameters of each food product. Changes in free fatty acids (FFA) content and oxidation markers can modify the organoleptic properties of HP-treated cheese. For this reason, the effect of high-pressure treatment on the FFA profile and lipid and protein oxidation of raw milk goat cheese (Ibores PDO cheese) was evaluated. HP treatment at 400 or 600 MPa, at 10 °C, for 7 min was applied at three different times during ripening (1, 30 or 50 days). The differences in FFA concentration detected after HP processing had equilibrated by the end of the ripening process, that is day 60. Finally, a significant increase in lipid oxidation was detected in HP-treated mature cheeses (60 days old) while no differences were found in protein oxidation. Further studies are necessary to understand the relationship between sensory properties and lipid oxidation changes induced by HP treatment of Ibores PDO cheese.

Effect of high-pressure-treated starter on ripening of Feta cheese

High-pressure (HP) treatment of cheese or of bacterial starters used in cheese manufacture has the potential to modify the cheese ripening process. The objective of the present study was to investigate the effect of a DVI starter mixture HP-treated at 200 MPa, at 20 °C for 15 min, on the ripening of Feta cheese. Microbiological and biochemical characteristics, including enzymatic activities, in cheese were studied throughout ripening. Mesophilic, thermophilic, and non-starter bacteria counts were not affected significantly (P > 0.05) by the starter HP treatment and the same was also true for lactate dehydrogenase activity, indicating that there was no enhancement of autolysis in the cheese matrix due to starter treatment. However, the use of HP-treated starter increased secondary proteolysis in cheese, as shown by levels of nitrogen soluble in 12% trichloroacetic acid and in 5% phosphotungstic acid. These findings were consistent with the significant (P < 0.05) increase of the area of small hydrophilic peptides in the HPLC profiles of Feta made with treated starter. Since residual chymosin activity and aminopeptidase activity on Leu-p-NA did not differ significantly compared to those of control cheese throughout ripening, an HP-treatment-induced modification of other proteolytic enzymes was possible. These findings, together with the slow decrease in pH during the first days of ripening, suggest that HP-treated starter can be used as an adjunct starter in Feta manufacture rather than as a regular starter.

RP-HPLC peptide profiling of cheese extracts: A study of sources of variation, repeatability and reproducibility

Peptide profiling of cheese extracts by RP-HPLC is widely used to study cheese quality and authenticity. Repeatability, reproducibility and the contribution of differences in sample/treatment, extraction, and the effect of the chromatographic run was studied. Chromatograms (108) of pH 4.6-soluble extracts from 180d Cheddar cheeses were used to evaluate the precision of the method and to quantify the effect of treatment and replicate cheese trial. Repeatability and reproducibility coefficient of variations of peaks/RT classes varied widely and no clear correlation was found between peak size and reproducibility. ANOVA of Principal Component Scores identified significant differences amongst cheeses and a trial effect. Partial Least Square Discriminant Analysis identified variables related to cheese treatment. Statistical process control methods were used to study the variability of replicate injections over the life of a single column showing the discriminatory power of RP-HPLC and giving possibilities to improve both process control and process optimisation.

Manufacture of low-sodium Minas fresh cheese: Effect of the partial replacement of sodium chloride with potassium chloride

We investigated the effect of sodium reduction by partial substitution of sodium chloride (NaCl) with potassium chloride (KCl) on the manufacture of Minas fresh cheese during 21 d of refrigerated storage. Four treatments of low-sodium Minas fresh cheese were manufactured, with partial replacement of NaCl by KCl at 0, 25, 50, and 75% (wt/wt), respectively. The cheeses showed differences in the content of moisture, ash, protein, salt, and lipid contents, as well as on the extent of proteolysis and hardness throughout the storage period. However, no difference was observed among treatments within each storage day tested. The partial substitution of NaCl by KCl decreased up to 51.8% the sodium concentration of the cheeses produced. The consumer test indicated that it is possible to manufacture a low-sodium Minas fresh cheese that is acceptable to consumers by partial substitution of NaCl by KCl at 25% (wt/wt) in the salting step.

EFFECT OF STARTER CULTURE ON THE QUALITY AND YIELD OF KARISH CHEESE MADE FROM BUFFALO’S MILK

Karish cheese was made from fresh buffaloes' skim milk (0.5% fat) using a commercial starter culture DOM 1® (Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris (1:1)) and with natural starter from good quality karish cheese. Four treatments were made by using 1 & 2% natural starter culture (YS-1 and YS-2, respectively) and with 1 & 2% of DOM 1® starter culture (DS-1 and DS-2, respectively). Yield of the resultant cheeses were calculated. Chemical, microbiological and sensory characteristics of cheeses were monitored when fresh and during 60 days of storage at 5±2°C. Gross composition of all resultant cheeses was within the Egyptian legal limits for Karish cheese. The highest cheese yield (25.4%) was obtained when 2% of DOM 1® starter culture was added (DS-2). This increase in the cheese yield of DS-2 was associated with an increase in the cheese moisture content by 2.7% compared with YS-1 and 1.1% compared with YS-2 treatments. The pH values were decreased during storage period, but both YS-1 and YS-2 treatments had lower pH-values than DS-1 and DS-2 treatments. The highest values of SN and SN/TN were observed in the DS-2 cheese treatment. This could be an indication of more proteolysis occurred when 2% of the DOM 1® starter culture was used. DS-1 and DS-2 treatments showed a reduction in the losses of TS and TN contents in the pickling solution during storage compared with YS-1 and YS-2 treatments. It was also observed that YS-1 and YS-2 treatments had higher total viable bacterial and mold & yeast counts than that in DS-1 and DS-2 treatments. On the other hand, there was a slight increase in the total sensory score of the DS-2 treatment. It can be concluded that manufacture of karish cheese by using 2% DOM 1® improved cheese yield, organoleptic properties and decreased losses of cheese components in pickling solution.

Biochemical patterns in ovine cheese: Influence of probiotic strains

This study was undertaken to evaluate the effect of lamb rennet paste containing probiotic strains on proteolysis, lipolysis, and glycolysis of ovine cheese manufactured with starter cultures. Cheeses included control cheese made with rennet paste, cheese made with rennet paste containing Lactobacillus acidophilus culture (LA-5), and cheese made with rennet paste containing a mix of Bifidobacterium lactis (BB-12) and Bifidobacterium longum (BB-46). Cheeses were sampled at 1, 7, 15, and 30 d of ripening. Starter cultures coupled with probiotics strains contained in rennet paste affected the acidification and coagulation phases leading to the lowest pH in curd and cheese containing probiotics during ripening. As consequence, maturing cheese profiles were different among cheese treatments. Cheeses produced using rennet paste containing probiotics displayed higher percentages of αS1-I-casein fraction than traditional cheese up to 15 d of ripening. This result could be an outcome of the greater hydrolysis of α-casein fraction, attributed to higher activity of the residual chymosin. Further evidence for this trend is available in chromatograms of water-soluble nitrogen fractions, which indicated a more complex profile in cheeses made using lamb paste containing probiotics versus traditional cheese. Differences can be observed for the peaks eluted in the highly hydrophobic zone being higher in cheeses containing probiotics. The proteolytic activity of probiotic bacteria led to increased accumulation of free amino acids. Their concentrations in cheese made with rennet paste containing Lb. acidophilus culture and cheese made with rennet paste containing a mix of B. lactis and B. longum were approximately 2.5 and 3.0 times higher, respectively, than in traditional cheese. Principal component analysis showed a more intense lipolysis in terms of both free fatty acids and conjugated linoleic acid content in probiotic cheeses; in particular, the lipolytic pattern of cheeses containing Lb. acidophilus is distinguished from the other cheeses on the basis of highest content of health-promoting molecules. The metabolic activity of the cheese microflora was also monitored by measuring acetic, lactic, and citric acids during cheese ripening. Cheese acceptability was expressed for color, smell, taste, and texture perceived during cheese consumption. Use of probiotics in trial cheeses did not adversely affect preference or acceptability; in fact, panelists scored probiotic cheeses higher in preference over traditional cheese, albeit not significantly.

Application of high-pressure treatment on ovine brined cheese: Effect on composition and microflora throughout ripening

Abstract Ovine brined cheese was high-pressure (HP) treated at 200 or 500 MPa for 15 min at 20 °C on the 15th day of ripening. Compared to control cheese, HP treatment did not affect significantly ( P > 0.05) the pH values, moisture, fat in dry matter, protein in dry matter and salt in moisture contents of cheeses at 90 days. The counts of total aerobic mesophilic bacteria, thermophilic lactococci, thermophilic lactobacilli and non starter lactic acid bacteria (NSLAB) were not affected by HP treatment of cheese at 200 MPa throughout ripening. After 90 days of ripening, the same microbial groups in cheese treated at 500 MPa were about 1.2, 3.6, 2.1 and 4 log units lower than in control cheese respectively. Coliforms were reduced faster at non detectable levels in HP treated cheeses than in control cheese. Regarding the bacterial enzymatic activities in cheese, aminopeptidase activity (Apep) was marginally favoured by both HP treatments. However, its activity was decreased at 90 days due probably to loss in brine. In contrast, lactate dehydrogenase (LDH) activity, following the bacteria cell lysis, was negatively affected by HP treatment at 500 MPa throughout ripening. Industrial relevance The data obtained from this work suggest that application of HP treatment under optimized conditions on ovine cheese in brine can be used to reduce effectively the undesirable microbial load in it and to cause moderate enhancement of aminopeptidase activity, without modifying its composition.

Monitoring the Chemical and Microbiological Changes During Ripening of Iranian Probiotic Low-Fat White Cheese

Problem statement: The objective of this experiment was to manufacture an Iranianlow fat probiotic cheese. Approach: Iranian white brine cheeses (4 trials) were made by varyingprocesses, i.e., lowering the fat content and use of probiotic adjunct culture on separate days. All types of cheeses were ripened at 13°C for 2 weeks and at 6°C to the end of ripering period. Cheeses were analyzed for the compositional, microbiological, color and sensory characteristics and also lipolysis and organic acid profile. The Cheese of each trial was sampled at 1, 15, 30, 45 and 60 days during ripening. Results: Decreasing the fat level resulted in significant increases (p<0.05) in the level of moisture, protein and pH of whey. The results show that probiotic cheeses had higher moisture and pH than cheeses with bacteria (p<0.05). There were no significant differences (p>0.05) between the concentration of L. acidophilus of cheese groups when the fat content of samples was reduced. The rate and extent of lipolysis in the full-fat cheese was higher than in the low-fat control cheese (p<0.05). Results also showed decreasing fat content and addition of adjunct culture to the cheese treatments decreased the acetic and lactic acid contents (p<0.05). Decreasing the fat content of cheese samples and use of both factor in the treatments increased the a* value in the samples. Low fat cheeses received higher flavor and odor scores than full fat cheeses. Also addition of adjunct culture significantly (p<0.05) decrease the texture score of manufactured cheeses. Conclusion: Therefore the results of this study showed that the Iranian probotic low fat cheese is a functional food. It has better flavor and odor than normal cheese and can be used in many cases like as heart disease and obesity.

Effect of high-pressure treatment on microbiology, proteolysis, lipolysis and levels of flavour compounds in mature blue-veined cheese

The effect of high-pressure (HP) treatment (400 MPa, 600 MPa) on ripening of mature 42-day-old Irish blue-veined cheese was studied. Counts of non-starter lactic acid bacteria, lactococci, yeasts, moulds, enterococci and total aerobic bacteria significantly decreased due to HP, with moulds being most sensitive and 600 MPa the most effective treatment. The levels of pH 4.6-soluble nitrogen and (12%) trichloroacetic acid-soluble nitrogen increased immediately after both HP treatments; however, after 28 days of storage, values were lower in HP-treated cheeses than in the control cheese. Urea-polyacrylamide gel electrophoresis showed increased breakdown of β-casein due to HP treatment at both 400 MPa and 600 MPa. Levels of free fatty acids were lower in HP-treated cheese than in the control, but not significantly so, and no significant changes could be observed in the level of flavour compounds of blue-veined cheese. Overall, HP treatment of blue-veined cheese reduced microbiological activity and decelerated proteolysis, with no statistically significant effects on development of flavour compounds. High-pressure treatment has been studied for the past 100 years; nevertheless, it was not applied in dairy industry, until recently, for a cheese spread. In this study, HP-induced inactivation of microbes and enzymes, which could arrest the ripening of high-quality mature (i.e., ripened) Irish farmhouse blue-veined cheese and thus extend shelf-life at optimal quality, was examined.

Dynamic Rheological Properties of Process Cheese: Effect of Ca and P Content, Residual Lactose, Salt-to-Moisture Ratio and Cheese Temperature

Four treatments of Cheddar cheese with two levels (high and low) of calcium (Ca) and phosphorus (P), and two levels (high and low) of residual lactose were manufactured. Each treatment was subsequently split prior to the salting step of cheese manufacturing process and salted at two levels (high and low) for a total of eight treatments. After two months of ripening, each treatment of Cheddar cheese was used to manufacture process cheese using a twin-screw Blentech process cheese cooker. NFDM, butter oil, trisodium citrate (emulsifying salt), and water were added along with Cheddar cheese for process cheese formulation. All process cheese food formulations were balanced for moisture (43.5%), fat (25%), and salt (2%), respectively. Dynamic rheological characteristics (G′ and G″) of process cheese were determined at 1.5Hz frequency and 750 Pa stress level by using a Viscoanalyzer during heating and cooling, temperature ranges from 30°C to 70°C then back to 30°C. High Ca and P content, and high S/M (HHH and HLH) cheeses had the significantly higher elastic (G′) and viscous (G″) modulus than other cheeses during heating from 30°C to 70°C, and cooling from 70°C to 30°C. No significant difference was observed among the other process cheeses during heating and cooling. Viscoelastic properties of process cheeses were also determined in terms of transition temperature (where G′ = G″), and tan δ during heating (30°C to 70°C). Cheeses with high Ca and P, high lactose, and high S/M content had higher transition temperature than low Ca and P, low lactose, and low S/M content process cheeses. Low Ca and P and low S/M content cheeses (LLL, LHH, LHL, HLL) exhibited more viscous characteristics than high Ca and P and high S/M content process cheeses (HHL, HLH, LLH, HHH) during heating from 30°C to 70°C. Low Ca and P, low lactose, low S/M content (LLL) process cheese was observed for highest tan δ values (0.39 to 1.43), whereas high Ca and P, high lactose, high S/M content process (HHH) had the least (0.33 to 1.06) during heating. This study demonstrates that different characteristics of natural cheese used in process cheese manufacturing have significant impact on process cheese rheological and viscoelastic properties.

Effect of high-pressure treatment of 1 day-old full-fat Cheddar cheese on subsequent quality and ripening

Abstract Full-fat Cheddar cheese was high-pressure (HP)-treated (400 MPa for 10 min at room temperature) 1 day post-manufacture. HP treatment resulted in an almost 100-fold reduction in starter bacteria numbers and delayed growth of non-starter lactic acid bacteria (NSLAB). HP treatment had little or no effect on primary proteolysis in cheese, consistent with measured plasmin and chymosin activities, which were unaffected by HP treatment. The mean concentrations of total lactate and d (−)- and l (+)-lactate were significantly reduced in HP-treated cheese relative to the control cheese during ripening. HP-treated cheese also had significantly higher fracture strain and fracture stress values and significantly lower flowability than control cheese throughout ripening. HP-treated cheese had altered colour values and was discriminated from the control cheese by descriptive sensory analysis. Overall, the selected HP treatment of Cheddar cheese seems to be of limited value for acceleration of ripening and, in fact, may be more useful for arresting or slowing down ripening. Industrial relevance To date there have been conflicting reports on the effectiveness of HP treatment in accelerating Cheddar cheese ripening. The aim of this study was to investigate the effects of HP treatment at 400 MPa for 10 min at room temperature on a range of cheese parameters over a 180-day ripening time. The overall conclusion suggests that the selected HP treatment has only minor benefits for manipulating the functional and sensory properties of Cheddar cheese.

Utilization of Microfiltration or Lactoperoxidase System or Both for Manufacture of Cheddar Cheese from Raw Milk

The objective of the present study was to determine if application of microfiltration (MF) or raw milk lactoperoxidase system (LP) could reduce the risk of foodborne illness from Escherichia coli in raw milk cheeses, without adversely affecting the overall sensory acceptability of the cheeses. Escherichia coli K12 was added to raw milk to study its survival as a non-pathogenic surrogate organism for pathogenic E. coli. Five replications of 6 treatments of Cheddar cheese were manufactured. The 6 treatments included cheeses made from pasteurized milk (PM), raw milk (RM), raw milk inoculated with E. coli K12 (RME), raw milk inoculated with E. coli K12 + LP activation (RMELP), raw milk inoculated with E. coli K12 + MF (MFE), and raw milk inoculated with E. coli K12 + MF + LP activation (MFELP). The population of E. coli K12 was enumerated in the cheese milks, in whey/curds during cheese manufacture, and in final Cheddar cheeses during ripening. Application of LP, MF, and a combination of MF and LP led to an average percentage reduction of E. coli K12 counts in cheese milk by 72, 88, and 96%, respectively. However, E. coli K12 populations significantly increased during the manufacture of Cheddar cheese for the reasons not related to contamination. The number of E. coli K12, however, decreased by 1.5 to 2 log cycles during 120 d of ripening, irrespective of the treatments. The results suggest that MF with or without LP significantly lowers E. coli count in raw milk. Hence, if reactivation of E. coli during cheese making could be prevented, MF with or without LP would be an effective technique for reducing the counts of E. coli in raw milk cheeses. The cheeses were also analyzed for proteolysis, starter and nonstarter lactic acid bacteria (NSLAB), and sensory characteristics during ripening. The concentration of pH 4.6 soluble nitrogen at 120 d was greater in PM cheese compared with the other treatments. The level of 12% trichloroacetic acid-soluble nitrogen at 120 d was greater in RM, RME, and RMELP cheeses compared with PM, MFE, and MFELP cheeses. This could be related to the fact that cheeses made from raw milk with or without LP (RM, RME, and RMELP) had greater levels of NSLAB compared with PM, MFE, and MFELP cheeses. Cheeses at 60 d, as evaluated by 8 trained panelists, did not differ in bitterness, pastiness, or curdiness attributes. Cheeses at 120 d showed no differences in acid-taste, bitterness, or curdiness attributes. Sensory analysis at 60 d showed that PM and MFELP cheeses had greater overall sensory acceptability than RM and RME cheeses. The overall sensory acceptability of the cheeses at 120 d showed that PM, MFE, and MFELP cheeses were more acceptable than RM and RME cheeses.

Effect of high-pressure treatments on proteolysis and texture of ewes’ raw milk La Serena cheese

La Serena cheeses, made from Merino ewes’ raw milk, were high-pressure (HP)-treated at 300 or 400 MPa for 10 min at 10 °C, on days 2 or 50 of ripening. Cheeses treated by HP on day 2 showed higher pH values than control cheese on day 3, but cheeses treated by HP on days 2 or 50 and control cheese had similar pH values on day 60. Breakdown of caseins was delayed by HP treatment of cheeses on day 2. Cheeses treated by HP on day 2 showed higher levels of hydrophilic peptides, lower levels of hydrophobic peptides, lower hydrophobic peptides: hydrophilic peptides ratios, and higher total contents of free amino acids than those of control cheese. HP treatment of cheese on day 50 scarcely affected proteolysis of 60-day-old cheeses. Fracturability, hardness and elasticity values of cheeses treated by HP on day 2 were higher than those of control cheese and of cheeses treated on day 50. Cheeses treated at 400 MPa on day 2 received the lowest scores for quality of taste from panellists, whereas the rest of HP-treated cheeses did not differ from control cheese.

Flavour development via lipolysis of milkfats: changes in free fatty acid pool

SummaryUnder the trade name lipolysed milkfat (LMF), concentrated cheese flavours obtained via enzymatic treatments of cheese (or other dairy substrates) have been made available in increasing numbers. In this research effort, (anhydrous) milkfats from cows, ewes and goats were used as substrates for production of cheesy flavours. Those milkfats were subjected to modifications brought about by ten different (commercial) lipases and one cutinase, and the free fatty acids released were analysed by high performance liquid chromatography. Both the degrees of hydrolysis and the free fatty acid profiles of the final products were similar to those reported for several LMF products, although specific keynotes could be pinpointed. Consequently, those milkfats may represent alternative raw materials for manufacture of cheesy flavours, while contributing to alleviate the problem derived from the increasing surplus of milkfat in Western countries.

Monitoring the Chemical and Textural Changes During Ripening of Iranian White Cheese Made with Different Concentrations of Starter

The effect of the concentration of starter inoculated to milk on the composition, free tyrosine-tryptophan content, microstructure, opacity, and fracture stress of Iranian White cheese (IWC) was studied during 50 d of ripening in brine. Three treatments of cheese were made using 1-fold (IWC1S), 2-fold (IWC2S), and 4-fold (IWC4S) concentrations of a direct-to-vat mesophilic mixed culture containing Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis as starter. As ripening progressed, moisture and protein contents of the treatments continuously decreased, whereas their total ash, salt, and salt in moisture contents increased. Fat content and pH of cheeses remained stable during ripening. The pH of cheese milk at the time of renneting, which decreased by increasing the concentration of starter (6.57, 6.49, and 6.29 for IWC1S, IWC2S, and IWC4S, respectively), significantly affected most of the chemical characteristics and opacity of cheese. Lower pH values at renneting decreased moisture and ash contents, whereas cheese protein content increased. The concentration of free tyrosine-tryptophan in curd increased at first 29 d but decreased between d 29 and 49 of aging. The changes observed in cheese whiteness followed the changes in moisture content of the treatments. As the concentration of starter inoculated to milk increased, the value of fracture stress at a given ripening time significantly decreased, leading to a less resistant body against applied stress. A similar trend was also observed for fracture strain during cheese ripening. The micrographs taken by scanning electron microscopy provided a meaningful explanation for decrease in the value of fracture stress. As the cheese ripening progressed or the concentration of starter increased, the surface area occupied by the protein fraction in cheese microstructure decreased, leading the way to lower the force-bearing component in cheese texture.

Effect of High-Pressure Treatment and a Bacteriocin-Producing Lactic Culture on the Proteolysis, Texture, and Taste of Hispánico Cheese

The effects of high-pressure treatment, by itself or in combination with a bacteriocin-producing culture added to milk, on the proteolysis, texture, and taste of Hispánico cheese were investigated. Two vats of cheese were manufactured from a mixture of cow and ewe milk. Milk in one vat was inoculated with 0.5% Lactococcus lactis ssp. lactis INIA 415, a nisin Z and lacticin 481 producer; 0.5% L. lactis ssp. lactis INIA 415-2, a bacteriocin-nonproducing mutant; and 2% of a commercial Streptococcus thermophilus culture. Milk in the other vat was inoculated with 1% L. lactis ssp. lactis INIA 415-2 and 2% S. thermophilus culture. After ripening for 15 d at 12°C, half of the cheeses from each vat were treated at 400MPa for 5min at 10°C. Ripening of high-pressure-treated and untreated cheeses continued at 12°C until d 50. High-pressure treatment of cheese made from milk without the bacteriocin producer accelerated casein degradation and increased the free AA content, but it did not significantly influence the taste quality or taste intensity of the cheese. Addition of the bacteriocin producer to milk lowered the ratio of hydrophobic peptides to hydrophilic peptides, increased the free AA content, and enhanced the taste intensity. The combination of milk inoculation with the bacteriocin producer and high-pressure treatment of the cheese resulted in higher levels of both hydrophobic and hydrophilic peptides but had no significant effect on the free AA content, taste quality, or taste intensity.

Transfer of 226Ra, 85Sr and 137Cs from milk to milk products&lt;/p&gt; &lt;/p&gt;

Transfer of 226Ra, 85Sr and 137Cs from cow and sheep milk to various Syrian dairy products has been evaluated. Dairy products include Kashkivan cheese, braided cheese, Haloom cheese, Sircassian cheese, liquid cheese, native cheese, cottage, thick yogurt, butter and milk cream. The results showed that the percentage of 226Ra, 85Sr and 137Cs transferred from cow milk to milk cream (Pt=food processing retention factor´processing efficiency´100%) has reached 32%, 16% and 7%, respectively. Butter and liquid cheese were found to have the lowest percentage of transferred 226Ra, 85Sr and 137Cs. Most of the obtained Pt values of the studied radionuclides in thick yogurt were relatively low in spite of the high processing efficiencies of thick yogurt. Moreover, the transfer, Pt, of the studied radionuclides from cow milk to the prepared cheese was higher than those values determined for sheep milk. This is due to differences in chemical compositions of each type of milk. On the other hand, the treatment of Native cheese, most commonly consumed cheese in Syria, with different concentrations of NaCl solutions showed that 137Cs was completely removed from cheese soaking in 5% NaCl solution (soaking time of 48 hours), while 40% of 226Ra and 80% of 85Sr were also decontaminated using 0-2.5% NaCl solutions and soaking time of 48 hours. Based on the obtained results, industrialization processes of the dairy products that resulted the removal of radionuclides have been identified.