Effect of On-Farm Heating and Storage of Milk on Cottage Cheese Yield

Effect of on-farm heat treatment of milk on cottage cheese yields was studied. Fresh, raw milk heated to 74°C for 10 s was cooled and stored for 7 days at 3°C. Control and experimental lots of milk were separated and pasteurized at 72°C for 15 s and were used to make cottage cheese. Microbiological, shelf-life, flavor, and texture studies showed the experimental lots of cheese were as good as or better than control lots. Yield of cottage cheese was significantly higher when made from heated milk.     

Methods to extend the shelf‐life of cottage cheese – a review

Under typical refrigeration conditions (4–7 °C), unopened fresh cottage cheese only lasts for approximately 3 weeks unless preservatives are added. The spoilage of cottage cheese during storage is primarily due to the growth of Gram‐negative psychrotrophic bacteria, yeasts and moulds. To extend its shelf‐life, along with a strict sanitation practice throughout the manufacturing process, an appropriate preservation approach is generally applied. Many methods to preserve cottage cheese have been reported. These can be classified into three categories, namely food‐grade chemicals, heat treatment and modified atmosphere packaging. In this review, factors responsible for the spoilage of cottage cheese during storage and the methods to extend its shelf‐life are discussed.     

Evaluation of PLA nanocomposite films on physicochemical and microbiological properties of refrigerated cottage cheese

A novel antimicrobial packaging system was prepared by incorporating TiO₂ or Ag nanoparticles into poly(lactic acid) (PLA) matrix. The effect of PLA, PLA/TiO₂, and PLA/TiO₂ + Ag film on the physicochemical and microbiological properties of Yunnan cottage cheese stored at 5 ± 1 °C for 25 days was investigated. The low density polyethylene (LDPE) film was used as the control. The weight loss, pH value, lactic acid bacteria count (LAB), texture, sensory quality, and antimicrobial activity were determined. Cheeses packed by PLA/TiO₂ and PLA/TiO₂+Ag film provided better retention in pH value, LAB, sensory quality, and antimicrobial activity compared with those packed by PLA and LDPE film. Migration of Ti and Ag nanoparticles was lower than the limit of 10 mg/kg as defined by EFSA for food contact materials. The results indicated that the incorporation of TiO₂ or Ag nanoparticles into PLA matrix could maintain cheese quality and prolong its shelf life to 25 days.

Practical applications

Yunnan cottage cheese is one of the most popular cheeses in China. However, the shelf life of unpacked Yunnan cottage cheese is only 5–7 days under refrigerated condition. PLA film incorporated with antimicrobial TiO₂ or Ag nanoparticles has great potential to prolong cheese shelf life. The novel packaging material may be an effective alternative for cheese preservation.     

Modified Atmosphere Packaging to Maintain Direct-Set Cottage Cheese Quality

Direct-set cottage cheese packaged in barrier containers was flushed with 100% CO₂ 75% CO₂:25% N₂, 100% N_2, or air, and stored at 4°C for 28 days. Quality was assessed by sensory, microbiological, and chemical tests. No change was observed in headspace gas composition during storage. Psychrotrophic and lactic acid bacteria counts increased for air-treated samples, but counts for cottage cheese packaged under modified atmospheres remained unchanged. Product discoloration was not observed. Acidity increased over storage life, but lactic acid did not contribute towards increased acidity. Sensory characteristics of cottage cheese packaged under modified atmospheres remained satisfactory after 28 days, with 100% CO₂ best.     

Liquid Drainage and Firmness in Full-fat, Lowfat, and Fat-free Cottage Cheese

Four different cottage cheese curds, as well as one full-fat (FFD), two lowfat (LF), and two fat-free (NF) dressings, were used to study liquid drainage’ and firmness of the products. After 10 hr at 4°C the volume of drained liquid after 1 and 7 days, was: FFD 77 to 38 mL, LF 59 to 2 mL, and NF 48 to 12 mL. Residual curd firmness was generally FFD > LF > NF. Both curd and dressing properties affected liquid drainage and firmness, indicating that using the same curd in the three cottage cheese varieties would likely result in variety differences in quality attributes.     

Use of acid whey protein concentrate as an ingredient in nonfat cup set-style yogurt

Acid whey resulting from the production of soft cheeses is a disposal problem for the dairy industry. Few uses have been found for acid whey because of its high ash content, low pH, and high organic acid content. The objective of this study was to explore the potential of recovery of whey protein from cottage cheese acid whey for use in yogurt. Cottage cheese acid whey and Cheddar cheese whey were produced from standard cottage cheese and Cheddar cheese-making procedures, respectively. The whey was separated and pasteurized by high temperature, short time pasteurization and stored at 4°C. Food-grade ammonium hydroxide was used to neutralize the acid whey to a pH of 6.4. The whey was heated to 50°C and concentrated using ultrafiltration and diafiltration with 11 polyethersulfone cartridge membrane filters (10,000-kDa cutoff) to 25% total solids and 80% protein. Skim milk was concentrated to 6% total protein. Nonfat, unflavored set-style yogurts (6.0 ± 0.1% protein, 15 ± 1.0% solids) were made from skim milk with added acid whey protein concentrate, skim milk with added sweet whey protein concentrate, or skim milk concentrate. Yogurt mixes were standardized to lactose and fat of 6.50% and 0.10%, respectively. Yogurt was fermented at 43°C to pH 4.6 and stored at 4°C. The experiment was replicated in triplicate. Titratable acidity, pH, whey separation, color, and gel strength were measured weekly in yogurts through 8 wk. Trained panel profiling was conducted on 0, 14, 28, and 56 d. Fat-free yogurts produced with added neutralized fresh liquid acid whey protein concentrate had flavor attributes similar those with added fresh liquid sweet whey protein but had lower gel strength attributes, which translated to differences in trained panel texture attributes and lower consumer liking scores for fat-free yogurt made with added acid whey protein ingredient. Difference in pH was the main contributor to texture differences, as higher pH in acid whey protein yogurts changed gel structure formation and water-holding capacity of the yogurt gel. In a second part of the study, the yogurt mix was reformulated to address texture differences. The reformulated yogurt mix at 2% milkfat and using a lower level of sweet and acid whey ingredient performed at parity with control yogurts in consumer sensory trials. Fresh liquid acid whey protein concentrates from cottage cheese manufacture can be used as a liquid protein ingredient source for manufacture of yogurt in the same factory.     

Prediction and Characterization of Normal and Vat-Failed Cottage Cheese

An acidification-heat-coagulation test has been developed for predicting cottage cheese vat-failure potential of milk. Milk is fist acidified to pH 5.06 at 10°C and then heated at a slow rate (1°C increment per min). Poor quality acidified milk (> 10⁴ CFU/ml) forms small curds at 37°C and below. Good quality acidified milk (< 10⁴ CFU/ml) will form small curds at higher temperatures. By this procedure cottage cheese vat-failure potential of milk containing different levels of psychrotrophs can be predicted. Normal and vat-failed cottage cheese curds are characterized by % of grit in cottage cheese and amount of curd fines in whey.     

CORRELATION OF TIME-TEMPERATURE INDICATOR RESPONSE WITH MICROBIAL GROWTH IN PASTEURIZED MILK

Commercially obtained pasteurized whole milk was stored at three constant temperatures (0°C, 5°C, and 10°C), and one variable temperature condition (cyclic exposure of 0°C for 14 days and 10°C for 2 days). Daily analyses were conducted to enumerate the growth of total bacteria, coliforms, psychrotrophs, and spore forming organisms in samples from each storage treatment. Microbial growth was correlated with the response of the I-POINT and LifeLine full-history time-temperature indicators. Response of the I-POINT model 2140 was strongly related to germination of the psychrotrophic bacteria, and significant correlations (r > 0.95) were found between total count enumeration and the LifeLine model 57 indicator.     

Effect of different storage conditions on coagulating properties and cheese quality of Withania coagulans extract

The effects of different storage conditions on the coagulating properties of extracts of Withania coagulans berries were investigated in terms of coagulation time, pH and quality attributes of cheese prepared from buffalo milk. The extracts were stored under different conditions, viz. room temperature (27 ± 3 °C), refrigerated storage (4 °C), frozen storage (?20 °C) and lyophilisation. The milk‐coagulating activity of the plant extracts was measured on a fortnightly basis for a period of 5 months. There was a nonsignificant change in pH and the milk coagulating properties of the lyophilised extract. Physiochemical analysis revealed that cheese prepared with lyophilised extract retained the highest content of ash (2.3%), fat (23.8%), total solids (48.7%) and crude protein (22.7%), and resulted in the highest cheese yield (17.6%) compared to other tested treatments. Thus, it is concluded that lyophilisation has good potential for storage of vegetable extract coagulants.     

A comparison of the effects of storage of raw milk at 2°C and 6°C on the yield and quality of Cheddar cheese

The advantages of storing raw milk, which is to be used for Cheddar cheese manufacture, at 2°C rather than at 6°C was examined. Storage of milk at the lower temperature effectively reduced the level of psychrotroph growth, and after 4 days the psychrotroph counts in samples stored at 2°C were 100-fold lower than those found in samples stored at 6°C. There was no advantage in terms of cheese yield in storing milks at the lower temperature, but an overall improvement in cheese quality was noted in samples produced from milk stored at 2°C.     

Electrophoretic studies of chhana whey and effect of temperature and time of storage on its quality

Chhana whey contains less protein than Cheddar cheese whey, acid casein and cottage cheese whey, and the protein composition is quite different. Electrophoretic methods demonstrated that most of the proteins in chhana whey were denatured, and there was considerable variation in the protein composition between samples of chhana whey and paneer whey obtained from different sources. The effect of storage temperature and time (up to 10 h at 40°C, 50°C, 60°C, 70°C and 80°C) on the quality of chhana whey was investigated. There were no significant changes in the pH and titratable acidity in any of these cases. Electrophoretic separation showed no qualitative changes in the protein composition pattern of chhana whey after up to 10 h of storage at 70°C.     

Influence of probiotic strains added to cottage cheese on generation of potentially antioxidant peptides,anti-listerial activity,and survival of probiotic microorganisms in simulated gastrointestinal conditions

Our objective was to evaluate the viability of probiotic microorganisms added to cottage cheese under simulated gastrointestinal conditions, the release of potentially-antioxidant peptides, and their antimicrobial effect on Listeria monocytogenes. Cottage cheeses were prepared in triplicate, incorporating Lactobacillus casei, Lactobacillus rhamnosus GG, the commercial mix YO-MIX™ 205, or a control without probiotic addition. The probiotic population remained at >10⁶ cfu g⁻¹ during 28 days of storage at 8 °C. Cheeses made with added probiotics showed an increased metabolic activity with higher levels of lactic and acetic acids. Higher numbers of potentially bioactive peptides were observed in cheeses added with probiotics. L. monocytogenes population was reduced by about one log cycle after 20 days of storage, in cheeses with probiotics added. Our results indicate that cottage cheese is a good vehicle for probiotic bacteria.     

Estimation of compaction and fouling effects during membrane processing of cottage cheese whey

Effects of transmembrane pressure on membrane performance and permeate flux were studied using pure water and cottage cheese whey. The transmembrane pressure was varied from 0·8 to 30 bar and the temperature was maintained at 21 ± 1°C. Mechanical deformation and compression of the ultrafiltration membrane used (MW cut-off 25 000 daltons) were considered to be the main factors responsible for the non-linearity of the relationship between processing pressure and water permeate flux rate. During membrane processing of cottage cheese whey, a further deviation from linearity was observed, possibly due to the effect of membrane fouling. Assuming that compaction effects were dependent only on the transmembrane pressure applied and not on the type of liquid being processed, compaction effects appeared to exceed fouling markedly in the pressure range 4–30 bar. Fouling and compaction effects were of the same order at pressures below 3 bar. In spite of the compaction phenomena, no substantial change in total solids flux was observed in membrane processing of cottage cheese whey.     

Effect of high pressure treatment on starter bacteria and spoilage yeasts in fresh lactic curd cheese of bovine milk

The effect of high pressure treatment on the inactivation of starter bacteria and spoilage yeasts in a commercially manufactured fresh lactic curd cheese was investigated. Fresh cheeses made from pasteurised bovine milk using a commercial Lactococcus starter preparation were vacuum-packaged and subjected to high pressure treatment within the range of 200 to 600 MPa for 5 min at ambient temperature (≤ 22 °C), and subsequently stored at 4 °C for up to 8 weeks. The number of viable starter bacteria and spoilage yeasts were enumerated immediately after treatment and at time intervals of 1, 2, 3, 4, 6, and 8 weeks during refrigerated storage. The viable count of Lactococcus in the cheeses treated at 200, 300, 400, and 600 MPa, showed approximate reductions of 2, 5, 6, and 7 log units under aerobic incubation conditions; and 3, 5, 6, and 7 log units under anaerobic incubation conditions. Treatment at 200 MPa did not significantly prevent the growth of yeasts, but in samples subjected to pressures ≥ 300 MPa, the growth of yeasts was effectively controlled for 6 to 8 weeks.Industrial relevanceAustralian specialty cheese manufacturers are interested in extending the shelf-life of selected products to extend domestic distribution and to take advantage of export opportunities. The potential domestic and export market of fresh lactic curd cheese can be hampered by relatively short shelf-life. High pressure processing (HPP), under optimised conditions, can be utilised as an effective tool to extend shelf-life while maintaining the quality attributes of this product.     

Effect of Milk Quality and Low Temperature Storage on Cheese Yield—A Summation

The effect of low temperature storage and milk quality on cheese yield was investigated. Raw milk was stored at 5, 7.5, and 10°C; grade A milk was stored for 6 to 12 d and manufacturing grade milk for up to 6 d. At 1-d (manufacturing grade) and 2-d (grade A) intervals, aliquots from each treatment were pasteurized and manufactured into cheese, and the resulting yield was compared with that obtained on d 0 for manufacturing and grade A milks, respectively. Each treatment was terminated when stored milk coagulated when pasteurized. Increase in total bacterial count ranged from one log cycle for high count manufacturing grade milk to more than three log cycles for low count grade A milk. Similar changes were observed for proteolytic and psychrotrophic populations. As stationary populations were approached, essentially all organisms were psychrotrophic, and most were proteolytic and lipolytic. Cheese yield was affected by initial psychrotrophic populations and length of time raw milk was stored. Recovery of cheese solids decreased by approximately .5% for manufacturing grade milk per day of storage up to 4 d. Further storage increased the loss of cheese solids, and loss of cheese yield correlated with increase in bacterial population. Yield loss appeared to be due to exocellular enzymes causing breakdown of proteins and fats. Protein degradation was accompanied by increased moisture in the curd. Cheese quality decreased as psychrotrophic populations increased. After pasteurization high count stored raw milk contained enough psychrotrophs to dominate the aging process, producing gassy unclean cheese. Stored milk cheese had a weak body with bitter flavors typical of that produced by heat-stable proteolytic enzymes.     

Oxidative status of Kefalotyri cheese during aerobic storage in the dark or under fluorescent light

Kefalotyri cheese made in December and April using milk from sheep grazing on pastures was aerobically kept, in the dark or under fluorescent light, for 40 days at 4°C. Unsaturated fatty acids, which were higher in April than in December cheese, were significantly (P < 0.05) decreased in all cheese samples under both storage conditions. According to lipid hydroperoxides, malondialdehyde and carbonyls changes, grated cheese samples stored under fluorescent light showed a higher protein and lipid oxidation as compared to samples stored in the dark. Sensory and colour characteristics were better for cheeses stored in the dark than those under fluorescent light.     

Effects of temperature,relative humidity,and protective netting on Tyrophagus putrescentiae (schrank) (sarcoptiformes: Acaridae) infestation,fungal growth,and product quality of cave-aged Cheddar cheese

Research was conducted to evaluate the effects of using food-grade ingredients on cave aged Cheddar cheese as either a surface coating or in nets to prevent infestation by Tyrophagus putrescentiae growth at different environmental conditions. Food grade coating formulations with 1) xanthan gum and propylene glycol (XG+PG) and 2) carrageenan, propylene glycol alginate, and PG (CG+PGA+PG) were made and infused into nets. Jars with cave aged Cheddar cheese cubes that were inoculated with 20 mites were stored in an environmental chamber for 14 d at temperature and relative humidity (RH) combinations of 10, 15, and 20 °C and 75 ± 2 and 85 ± 2% RH. When averaged over RH, mite counts were fewer on control cheese cubes at 10 °C when compared to 15 °C and 20 °C, regardless of whether nets were used or not. However, mites were able to reproduce on untreated cheese cubes at all temperatures. The CG+PGA+PG and XG+PG coatings and nets controlled mite reproduction, as evidenced by harboring less than the initial inoculation level of 20 mites. Sensory results indicated that CG+PGA+PG and XG+PG coated Cheddar cheese at 10 °C and 75% RH and netted Cheddar cheese at 10 or 15 °C and 75% RH did not differ (P > 0.05) from the control with respect to sensory attributes. The treatments at 15 °C and 85% RH and 20 °C caused the cheese to be softer and more bitter than control cheese. In conclusion, the CG+PGA+ 40% PG and XG+40% PG treatments of both coatings and nets inhibited the growth of mites, and the use of nets lessened the impact of food grade coatings on the sensory properties of the Cheddar cheese.     

Shelf-life of a Greek whey cheese under modified atmosphere packaging

“Anthotryros” cheese was packaged under vacuum (VP) or modified atmosphere (MAP) and stored at 4 or 12 °C. MAP mixtures were 30%/70% CO₂/N₂ (M1) or 70%/30% CO₂/N₂ (M2), while VP was taken as the control sample. Microbiological results showed that M1 and M2 delayed microbial growth compared with VP samples. Of the two modified atmospheres, gas mixture M1 was the most effective for inhibition of growth of mesophilic bacteria. Based primarily on sensory evaluation, the use of both MAP conditions extended the shelf-life of fresh Anthotyros cheese stored at 4 °C by ca. 10 days (M1) or 20 days (M2) compared with VP, and by ca. 2 days (M1) and 4 days (M2) at 12 °C, with cheese maintaining good sensory characteristics.     

Kinetics of Folacin Destruction in Swiss Chard During Storage

The folacin activities in fresh Swiss chard leaves stored in open air at 4, 21, 35 and 40°C were determined by a microbiological assay using Lactobacillus casei. At 21°C the leaves were also stored in plastic bags and under moist conditions. Folacin was most stable when the vegetable was stored in plastic bags, followed by the moist condition, and least stable in open air at 21°C. The degradation of folacin in Swiss chard under all conditions followed firstorder kinetics. The temperature dependent folate degradation conformed to the Arrhenius equation and the activation energy was 24 kcal/mole.