Evaluation of Alternative Methods to Increase Calcium Retention in Cottage Cheese Curd

The effect of several alternative methods including addition of rennet, addition of carrageenan and use of 2:1 (v/v) preconcentrated skim milk by ultrafiltration (UF) upon calcium retention, yield, composition and sensory properties of dry curd cottage cheese was investigated. Although each of the processing methods resulted in the manufacture of dry curd cottage cheese with different compositions and properties, none of them was satisfactory for increasing calcium retention. Added carrageenan bound additional whey proteins, added rennet interfered with curd syneresis and whey expulsion during cooking and use of UF preconcentrated skim milk resulted in an increase in yield, total solids and protein of the curd.     

Extraction of Whey Proteins with Magnesium and Zinc Salts

A method was developed for the extraction of protein from cottage cheese whey with magnesium and zinc salts. After neutralization of the whey, both magnesium and zinc salts (at 4 and 2% wt/vol, respectively) precipitated most of the protein nitrogen plus some nonprotein nitrogen and lactose. Calcium at these concentrations was only partially effective. Yields of dried precipitate obtained from cottage cheese whey containing approximately 7% solids ranged from 25 to 34 g/L. Precipitates contained 16 to 21% protein and from 11 to 24% lactose; the remainder was ash. Zinc was the preferred reagent because it was effective at neutral pH; magnesium, alone or with calcium, required alkaline pH for thorough precipitation of protein. All reagents tested were effective precipitants of whey protein in a one-step procedure at room temperature.     

Short communication: Production of cottage cheese fortified with vitamin D

The availability of alternative food products fortified with vitamin D could help decrease the percentage of the population with vitamin D deficiency. The objective of this study was to fortify cheese with vitamin D. Cottage cheese was selected because its manufacture allows for the addition of vitamin D after the draining step without any loss of the vitamin in whey. Cream containing vitamin D (145 IU/g of cream) was mixed with the fresh cheese curds, resulting in a final concentration of 51 IU/g of cheese. Unfortified cottage cheese was used as a control. As expected, the cottage cheese was fortified without any loss of vitamin D in the cheese whey. The vitamin D added to cream was not affected by homogenization or pasteurization treatments. In cottage cheese, the vitamin D concentration remained stable during 3 weeks of storage at 4°C. Compared with the control cheese, the cheese fortified with vitamin D showed no effects of fortification on cheese characteristics or sensory properties. Cottage cheese could be a new source of vitamin D or an alternative to fortified drinking milk.     

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.     

Stabilization of returned dairy products by ensiling with straw and molasses for animal feeding

Returned dairy products which are transferred to landfills might add to the environmental pollution. Such products have a high nutritional value for ruminants, but they should be stabilized to enable their use as cattle feed. The purpose of the current study was to examine stabilization of returned dairy products by ensiling in combinations with straw and molasses for animal feeding. Treatments included combinations of milk and cottage cheese with straw and molasses. Results indicate that such products ensile well with straw, and after 3 d of ensiling the pH decreased to around 4.0. It was necessary to supplement cottage cheese with molasses, to supply a carbohydrate source for the lactic acid fermentation. The major fermentation product was lactic acid. Percentage of ammonia N (of total N) was generally higher in the silages made with cottage cheese than in those made with milk; the highest percentage (16%) was measured in the second experiment in the silages prepared with cottage cheese and straw. The study indicates the potential of stabilizing returned dairy products for animal feeding along with straw and molasses. There may also be potential for large dairy farms, or groups of smaller farms, to ensile waste milk with straw for later use as feed.     

Cottage Cheese from Ultrafiltered Skim Milk Retentates in Industrial Cheese Making

Ultrafiltered skim milk retentates were transported to a large industrial cottage cheese plant for milk supplementation leading to cottage cheese. The resulting industrial products were observed for composition, yields, whey component losses, and quality.Ten lots of small curd cottage cheese were made in vats containing up to 6593 kg skim milk. Retentate supplemented skim milks, concentrated approximately 10% (1.1:1) and 20% (1.2:1) in total protein, were very similar in initial composition to the controls. Mean cheese yield values from milks supplemented to 1.2:1 total protein were significantly higher than mean unsupplemented control milk values. Cheese yield efficiencies, per kilogram total solids, were also significantly higher in the retentate cheese but not when calculated per kilogram total protein.Total solids, total protein, and ash were higher in cottage cheese wheys from retentate supplemented cheese and were directly related to retentate supplementation concentration. Mean whey component loss per kilogram cheese exhibited significant decreases from milks of higher retentate supplementation. Retentate supplemented skim milk produced industrial cottage cheese of comparable quality to cheese made from unsupplemented control skim milks.     

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.     

Antagonistic action of Lactobacillus delbrueckii ssp. lactis RM2-5 toward spoilage organisms in cottage cheese

Cells of Lactobacillus delbrueckii ssp. lactis RM2-5 were added to cottage cheese stored at 7 degrees C in different amounts to determine if they would inhibit the growth of Pseudomonas fluorescens, also inoculated into the cheese samples. In addition, experiments were conducted in which no spoilage organisms were added to determine the effect of the lactobacilli on the natural background flora in the cottage cheese. For most experiments, as the numbers of lactobacilli increased, the numbers of spoilage organisms were lower than in the control on any given day of storage. In cheese inoculated with P. fluorescens, the numbers of spoilage organisms in the control had increased 5 log cycles by d 7, whereas the treatment containing the highest level of L. delbrueckii ssp. lactis RM2-5 (1.0 x 10(9) cfu/g) had not, and did not, increase over the course of the 21-d study. In the experiments where no spoilage organisms were added, lactobacilli significantly retarded the growth of gram-negative bacteria in the cheese. However, in these experiments, mold growth on the samples became a limiting factor during extended storage. The results of these experiments indicate that lactobacilli could be effective at helping control gram-negative spoilage bacteria in cottage cheese, thus potentially extending its shelf life.     

Cottage cheese whey as an ingredient of cottage cheese dressing mixes

The objective of this study was to formulate and develop a good quality cottage cheese dressing using acid whey as the main ingredient. Up to 72% of cottage cheese whey was used in the dressing mixes. The percentage of fat (4.10–5.05%) and total solids (19.41–20.24%) approached the desired level and was within the legal limits for regular cottage cheese. Sensory evaluation scores for flavour, body/texture and appearance were not adversely affected by the use of acid whey. The sensory evaluation scores for all four products made with whey- or skimmed milk-based dressings were higher than the commercial control.     

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.     

农家干酪在中国的发展优势

干酪的营养价值极高,是乳品行业将来发展的方向。从农家干酪的营养和加工特点出发,介绍了农家干酪所具有的发展优势,阐述了农家干酪的研究状况,并对农家干酪在中国的开发提出了一些建议。     

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.     

Biological study on the effect of supplementing wheat flour with fish protein concentrate

The protein quality of 4 Egyptian pastries made from different combinations of flour and fish protein concentrate (0%, 4% and 6%) was measured by rat growth study. Weight gain, feed consumption and PER were determined. Weight gain of rats fed cottage cheese crescents was higher than that fed date bars followed by that fed brouche, then rats fed salty sticks. Feed consumed by rats fed with the corresponding commercial pastries was low except in date bars group. Commercial pastries led to low weight gain and low PER values. Supplementing wheat flour with 6% fish protein concentrate gave the highest weight gain and the highest PER values.     

Impact of low concentration factor microfiltration on milk component recovery and Cheddar cheese yield

The effect of microfiltration (MF) on the composition of Cheddar cheese, fat, crude protein (CP), calcium, total solids recovery, and Cheddar cheese yield efficiency (i.e., composition adjusted yield divided by theoretical yield) was determined. Raw skim milk was microfiltered twofold using a 0.1-microm ceramic membrane at 50 degrees C. Four vats of cheese were made in one day using milk at lx, 1.26x, 1.51x, and 1.82x concentration factor (CF). An appropriate amount of cream was added to achieve a constant casein (CN)-to-fat ratio across treatments. Cheese manufacture was repeated on four different days using a randomized complete block design. The composition of the cheese was affected by MF. Moisture content of the cheese decreased with increasing MF CF. Standardization of milk to a constant CN-to-fat ratio did not eliminate the effect of MF on cheese moisture content. Fat recovery in cheese was not changed by MF. Separation of cream prior to MF, followed by the recombination of skim or MF retentate with cream resulted in lower fat recovery in cheese for control and all treatments and higher fat loss in whey when compared to previous yield experiments, when control Cheddar cheese was made from unseparated milk. Crude protein, calcium, and total solids recovery in cheese increased with increasing MF CF, due to partial removal of these components prior to cheese making. Calcium and calcium as a percentage of protein increased in the cheese, suggesting an increase in calcium retention in the cheese with increasing CF. While the actual and composition adjusted cheese yields increased with increasing MF CF, as expected, there was no effect of MF CF on cheese yield efficiency.     

Effect of Proteolytic Activity of Streptococcus cremoris on Cottage Cheese Yields

Using only a proteinase-negative variant of Streptococcus cremoris UC310 to manufacture cottage cheese increased theoretical yields by 2.26% compared wth the proteinase-positive parent. Yield differences between positive and negative variants were strain dependent and not detected with variants of UC73 and UC97. Growth of proteinase-negative variants in bulk culture required pH control and addition of sufficient nitrogenous stimulant to provide carry-over activity into the cheese milk. Cultures developed normally when the bulk medium contained 5% of a blend of yeast extract and casein hydrolyzate. Proteinase-negative culture successfully completed acidification of cottage cheese milk after direct acidification to pH 5.2 with phosphoric acid. Lactic culture strain selection is suggested for maximizing product yields with proteinase-negative cultures.     

Biological study on the effect of supplementing wheat flour with fish protein concentrate.

The protein quality of 4 Egyptian pastries made from different combinations of flour and fish protein concentrate (0%, 4% and 6%) was measured by rat growth study. Weight gain, feed consumption and PER were determined. Weight gain of rats fed cottage cheese crescents was higher than that fed date bars followed by that fed brouche, then rats fed salty sticks. Feed consumed by rats fed with the corresponding commercial pastries was low except in date bars group. Commercial pastries led to low weight gain and low PER values. Supplementing wheat flour with 6% fish protein concentrate gave the highest weight gain and the highest PER values.     

脱脂乳热处理对农家干酪品质及其加工的影响

乳制品生产离不开热处理，用于加工的脱脂乳的品质和微生物数量对农家干酪的品质和生产中关键环节的控制都有重要的影响。针对脱脂原料乳经不同热处理后对乳中蛋白质，农家干酪的产率厦加工品质的影响进行了探讨。     

The effect of commonly used dairy processing techniques and unit operations on the equol content of dairy products

Since a large portion of the milk consumed by human is processed, the aim of this study was to determine possible changes in equol content upon processing milk. Individual milks with different levels of equol content were collected from the morning milking to make skimmed milk and cream, as well as pasteurised and sterilised full fat milks. Pasteurised milk was further processed into yoghurt, kefir, cottage cheese and whey. Yoghurt and kefir were also produced from sterilised milk. Equol content was not affected by either pasteurisation or sterilisation. Compared with raw milk, a higher concentration of equol was measured in skimmed milk, but equol content in cream was lower. The concentration of equol remained unchanged after yoghurt production but was reduced by more than 50% after kefir production. The equol content in whey was low compared with that of raw milk, while it increased sharply in cottage cheese.