Development of a Continuous Process for the Production of Ricotta Cheese

A process was developed for the continuous production of Ricotta cheese. The process consists of multistep heating to 92°C, whey protein denaturation in a 10-min holding tube, acid injection to induce coagulation (2.5% citric acid), curd formation in a clear plastic holding tube (10 min), followed by separation of curd from deproteinated whey on a nylon conveyer belt. The process resulted in 98.1% removal of the recoverable solids. Recoveries of protein and fat were 99.5 and 99.6%, respectively.Cheese, prepared from a blend of 80% sweet whey and 20% whole milk, contained 33.5% total solids, 16.30% protein, and 11.6% milk fat. Italian Ricotta, prepared from whey ultrafiltered 4.5 to 1, contained 19.8% total solids, 15.9% protein, and 2.4% fat. The pH of Ricotta prepared from the whey and milk blend (80:20) ranged from 5.6 to 5.8, whereas pH of Ricotta prepared from only ultrafiltered whey (4.5 to 1) was 5.7 to 5.9.The process has advantages over other conventional mechanized cheese processes in terms of reduced capital and operating costs. The process is suitable for cheese factories that may wish to produce Ricotta as a protein base for other food products, such as cream cheese, processed cheese, snack food dips, and quiches.     

Effect of a pre-treatment of milk with high pressure homogenization on yield as well as on microbiological, lipolytic and proteolytic patterns of "Pecorino" cheese

The principal aim of this work was to compare Pecorino cheeses obtained from ewes' milk previously subjected to high pressure homogenization (HPH) at 100 MPa with those produced from raw and heat treated ewes' milk. The HPH milk treatment induced a significant increase of the cheese yield and caused a reduction of enterococci, lactococci and yeasts in the curds. Enterococci cell loads remained at lower levels in cheeses obtained from HPH milk over the ripening period. Analyses of free fatty acids, Sodium Dodecil Sulphate (SDS)-PAGE profiles, Gas Chromatography-Mass Spectrometry-Solid Phase Microextraction (GC-MS-SPME) measurements of volatile compounds and sensory traits evidenced that the pressure treatment can be regarded also as a useful tool to differentiate products obtained from the same raw material. In fact such a milk treatment induced a marked lipolysis, an early proteolysis, a relevant modification of the volatile molecule profiles and sensory properties of Pecorino cheese.     

Spreadable ricotta cheese with hydrocolloids: Effect on physicochemical and rheological properties

Ricotta cheese was selected to develop a novel food product. Ricotta is easily obtained from the precipitation of whey and milk proteins, through the application of heat and acidification. This product is characterised by its compact, finely granulated and crumbly mass of limited shelf life. Unlike the conventional methods for ricotta elaboration, a novel processing step was introduced to improve spreadability. The effect of hydrocolloids addition on physicochemical, mechanical and rheological properties was evaluated during storage. Hydrocolloids had a positive effect on the cheese matrix regarding microstructure and rheological properties. Samples showed acceptable physicochemical properties (compared with the control) during storage. Addition of hydrocolloids attenuated syneresis. Preliminary results showed that the best formulation was ricotta cheese containing high gelification capacity gelatin. Results of this study may contribute to the development of a novel dairy product.     

Distribution and stability of Aflatoxin M1 during processing and ripening of traditional white pickled cheese

The distribution of aflatoxin M₁ (AFM₁) has been studied between curd, whey, cheese and pickle samples of Turkish white pickled cheese produced according to traditional techniques and its stability studied during the ripening period. Cheeses were produced in three cheese-making trials using raw milk that was artificially contaminated with AFM₁ at the levels of 50, 250 and 750 ng/l and allowed to ripen for three months. AFM₁ determinations were carried out at intervals by LC with fluorescence detection after immunoaffinity column clean-up. During the syneresis of the cheese a proportionately high concentration of AFM₁ remained in curd and for each trial the level was 3.6, 3.8 and 4.0 times higher than levels in milk. At the end of the ripening, the distribution of AFM₁ for cheese/whey + brine samples was 0.9, 1.0 and 1.3 for first, second and third spiking respectively indicating that nearly half of the AFM₁ remained in cheese. It has been found that only 2-4% of the initial spiking of AFM₁ transferred into the brine solution. During the ripening period AFM₁ levels remained constant suggesting that AFM₁ was quite stable during manufacturing and ripening.     

Sensory Changes During Ripening of Raw Ewes' Milk Cheese Manufactured With and Without the Addition of a Starter Culture

ABSTRACT: This study characterizes and compares the sensory aspects of raw ewes' milk cheeses manufactured with and without the addition of a starter culture using specifically developed sensory terminology. Furthermore, overall organoleptic quality was assessed at each ripening stage. Two different raw ovine milk cheese batches were manufactured with and without the addition of a freeze-dried starter. Sensory differences in odor, flavor, and texture were related to starter and raw milk flora activities during manufacturing and ripening. Cheeses made with the addition of a starter culture were scored higher by quality experts. Cheeses manufactured without a starter culture received higher scores for dirty and animal attributes, such as rennet, butyric, sharp, pungent, and brine, possibly related to lower quality scores. Conclusions reached in the present study coincide with previous ones; however, by using a sensory lexicon specifically developed for ewes' milk cheeses, it has been possible to describe slight and specific differences in the cheeses.     

硬质发酵干酪加工设备简述

在简要说明我国发展干酪生产必要性的基础上,以切达干酪加工生产为例,从原奶的预处理、凝块的形成和加工、乳清排放以及质构化和盐化、灌装和压榨、包装和储存等5个方面详细介绍了国内外硬质干酪产品加工设备类型和使用情况,以期推动我国干酪加工设备的国产化进程。     

Stability of aflatoxin M in milk.

This three-part study was designed to determine aflatoxin M recovery from pasteurized and/or stored cow's milk. (a) Aflatoxin M was added to samples of raw Holstein milk at a concentration of 2.0 mug/liter. Half of each sample then was pasteurized at 63 C for 30 min, and both raw and pasteurized portions were stored at 4 C up to 17 days. (b) Samples of raw milk, pasteurized (77 C, 16 s) skim milk, dry cottage cheese curd, and cottage cheese whey were taken from a commercial operation in an area in which natural contamination had been encountered. (c) Milk from a cow dosed with aflatoxin B1 was stored frozen (-18 C) in bulk and in assay-size sample containers for 120 days. Aflatoxin M was recovered completely after either storage or pasteurization in (a) and (b). In (c), a recovery deficiency was detectable after 68 days of storage, which increased to 45% of the original value by 120 days. These observations differ from those of others in that loss of aflatoxin M was significant after pasteurization or storage of raw milk, totaling 87% loss after 120 days of frozen storage. Aflatoxin M partitioning between curd and whey in the preparation of cottage cheese agrees with more recent studies, but differs from previous reports. Three possible explanations for the differences are offered.     

Fate of Aflatoxin M1 during Manufacture and Storage of Feta Cheese

ABSTRACT:  The effect of feta cheese manufacture on aflatoxin M₁ (AFM₁) content was studied using an enzyme immunoassay technique. Feta cheese was made from milk spiked with 1 and 2 μg AFM₁ per kilogram milk. Pasteurization at 63 °C for 30 min caused <10% destruction of AFM₁. During cheese making, the remaining AFM₁ in milk was partitioned between curd and whey with two-thirds retained in the curd and one-third going into the whey. Cheeses were then stored for 2 mo in 8%, 10%, and 12% brine solutions at 6 and 18 °C. There was a 22% to 27% reduction of AFM₁ during the first 10 d of storage, with slightly more loss as salt concentration increased and when the cheese was stored at 18 °C. Further storage caused only slight decrease in AFM₁ and after 30 d of brining there was no difference in AFM₁ content of the cheese based upon salt concentration of the brine. At 18 °C, no further losses of AFM₁ occurred after 30 d, and at 6 °C, there was continued slight decrease in AFM₁ levels until 50 d. After 60 d of brining, there was a total loss of 25% and 29% of the AFM₁ originally present for cheese brined at 6 and 18 °C, respectively. Thus, the combination of pasteurization, conversion of milk into feta cheese, and at least 50 d storage of cheese in brine caused a total loss of about 50% of the AFM₁ originally present in the raw milk.     

Use of human lysozyme transgenic goat milk in cheese making: effects on lactic acid bacteria performance

Genetically engineered goats expressing elevated levels of the antimicrobial enzyme lysozyme in their milk were developed to improve udder health, product shelf life, and consumer well-being. The purpose of this study was to evaluate the effect of lysozyme on the development of lactic acid bacteria (LAB) throughout the cheese-making process. Raw and pasteurized milk from 7 lysozyme transgenic goats and 7 breed-, age-, and parity-matched nontransgenic controls was transformed into cheeses by using industry methods, and their microbiological load was evaluated. The numbers of colony-forming units of LAB were determined for raw and pasteurized goat milk, whey, and curd at d 2 and at d 6 or 7 of production. Selective plating media were used to enumerate lactococcal species separately from total LAB. Although differences in the mean number of colony-forming units between transgenic and control samples in raw milk, whey, and cheese curd were non-significant for both total LAB and lactococcal species from d 2 of production, a significant decrease was observed in both types of LAB among d 6 transgenic raw milk cheese samples. In pasteurized milk trials, a significant decrease in LAB was observed only in the raw milk of transgenic animals. These results indicate that lysozyme transgenic goat milk is not detrimental to LAB growth during the cheese-making process.     

A possible solution to minimise scotta as a food waste: A sports beverage

A pilot study trial was performed on ready‐to‐drink beverages produced in a small‐scale dairy plant starting from Ricotta whey (scotta) with the addition of fruit puree and starter cultures. Microbiological shelf life was evaluated at 4 and 12 °C. At 4 °C, the product showed moderate total viable counts until the end of the trial (~5 log cfu/mL). Yeasts proved to be the specific spoilage microorganisms of the product. When applying a thermal abuse at 20 °C for 6 h, total viable count did not increase. The addition of fruit puree changed the volatile profile of the beverages compared to raw scotta.     

Hot Brine Stretching and Molding of Low Moisture Mozzarella Cheese Made from Retentate-Supplemented Milks

Low moisture Mozzarella cheese curd was made from cheese milks supplemented to 1.2:1 and 1.4:1 fat and protein with 4.5:1 retentates of ultrafiltration stretched and molded in hot 10% brine.Retentate supplementation improved cheese yield and yield efficiencies. Retentate-supplemented cheese had higher protein and fat and lower moisture than controls. Maximum total solids and yields were obtained from cheese stretched in hot brine. Such cheese showed more uniform salt distribution but slightly lower salt concentration than controls. More loss of fat occurred in whey in control cheese stretched in hot water. Hot brine stretching of low moisture Mozzarella cheese made from retentate-supplemented milk suggests savings in time, space, equipment, and labor without detrimental effects on cheese color and meltability.     

Behavior of Escherichia coli O157:H7 during the manufacture and aging of Gouda and stirred-curd Cheddar cheeses manufactured from raw milk

This study was conducted to examine the fate of Escherichia coli O157:H7 during the manufacture and aging of Gouda and stirred-curd Cheddar cheeses made from raw milk. Cheeses were manufactured from unpasteurized milk experimentally contaminated with one of three strains of E. coli O157:H7 at an approximate population level of 20 CFU/ml. Samples of milk, whey, curd, and cheese were collected for enumeration of bacteria throughout the manufacturing and aging process. Overall, bacterial counts in both cheese types increased almost 10-fold from initial inoculation levels in milk to approximately 145 CFU/g found in cheeses on day 1. From this point, counts dropped significantly over 60 days to mean levels of 25 and 5 CFU/g in Cheddar and Gouda, respectively. Levels of E. coli O157:H7 fell and stayed below 5 CFU/g after an average of 94 and 108 days in Gouda and Cheddar, respectively, yet remained detectable after selective enrichment for more than 270 days in both cheese types. Changes in pathogen levels observed throughout manufacture and aging did not significantly differ by cheese type. In agreement with results of previous studies, our results suggest that the 60-day aging requirement alone is insufficient to completely eliminate levels of viable E. coli O157:H7 in Gouda or stirred-curd Cheddar cheese manufactured from raw milk contaminated with low levels of this pathogen.     

Distribution and stability of aflatoxin M1 during processing, ripening and storage of Telemes cheese

Telemes cheeses were produced using milk that was artificially-contaminated with aflatoxin M1 at the levels of 0.050 and 0.100 microg/l. The cheeses produced in the two cheese-making trials were allowed to ripen for 2 months and stored for an additional 4 months to simulate commercial production of Telemes cheese. Concentrations of aflatoxin M1 in whey, curd, brine, and the produced cheeses were determined at intervals by liquid chromatography and fluorometric detection coupled with immunoaffinity column extraction. Concentrations of aflatoxin M1 in the produced curds were found to be 3.9 and 4.4 times higher than those in milk, whereas concentrations in whey were lower than those in curd and milk. Aflatoxin M1 was present in cheese at higher concentrations at the beginning than at the end of the ripening/storage period, and it declined to concentrations 2.7 and 3.4 times higher than those initially present in milk by the end of the sixth month of storage. Concentrations of aflatoxin M1 in brine started low and increased by the end of the ripening/storage period but only a portion of the amounts of aflatoxin M1 lost from cheese was found in the brine. Results showed that Telemes cheeses produced from milk containing aflatoxin M1 at a concentration close to either the maximum acceptable level of 0.05 microg/l set by the European union (EU) or at double this value, will contain the toxin at a level that is much lower or slightly higher, respectively, than the maximum acceptable level of 0.250 microg of aflatoxin M1/kg cheese set by some countries.     

Fate of ivermectin residues in ewes' milk and derived products

The fate of ivermectin (IVM) residues was studied throughout the processing of daily bulk milk from 30 ewes (taken up to 33 d following subcutaneous administration of 0.2 mg IVM/kg b.w.) in the following milk products: yoghurt made from raw and pasteurized milk; cheese after pressing; 30- and 60-day ripened cheese; and whey, secondary whey and whey proteins obtained after cheese-making (albumin cheese). The concentration of the H2B1a component of IVM was analysed in these dairy products using an HPLC method with fluorescence detection. The mean recovery of the method was, depending on the matrix, between 87 and 100%. Limits of detection in the order of only 0.1 microg H2B1a/kg of product were achieved. Maximum concentrations of IVM were detected mostly at 2 d after drug administration to the ewes. The highest concentration of IVM was found on day 2 in 60-day ripened cheese (96 microg H2B1a/kg cheese). Secondary whey was the matrix with the lowest concentration of IVM (<0.6 microg H2B1a/ kg). Residue levels fell below the limits of detection between day 5 (for secondary whey) and day 25 (for all cheese samples). In the matrices investigated, linear correlations between daily concentrations of IVM, milk fat and solid content were evident. During yoghurt production, fermentation and thermal stability of IVM was observed. During cheese production, approximately 35% of the IVM, present in the raw (bulk) milk samples, was lost. From the results it was concluded that the processing of ewes' milk did not eliminate the drug residues under investigation. The consequences of IVM in the human diet were discussed. Milk from treated animals should be excluded from production of fat products like cheese for longer after treatment with IVM than for lower fat products.     

Improvement of low fat mozzarella cheese properties using denatured whey protein

Mozzarella cheese was made from buffalo milk (6% fat) or from partially skimmed buffalo milk (2 and 4% fat) with 0.5 and 1% denatured whey protein. Adding whey protein to buffalo milk decreased rennet coagulation time and curd tension whereas increased curd synaeresis. Addition of whey protein to cheese milk increased the acidity, total solids, ash, salt, salt in moisture, also some nitrogen fractions. The meltability and oiling‐off values increased but the calcium values of mozzarella cheese decreased. The sensory properties of low fat mozzarella cheese were improved by addition of whey protein to the cheese milk.     

Effect of Curd Healing Time on Stirred Curd Cheese Yield

Cheese was manufactured with variable heal times to determine the effect of curd healing time on stirred curd cheese yield. A randomized complete block design with three treatments (vat healing times from cut to cook) was replicated six and four times in studies 1 and 2, respectively, for a total of 30 vats of stirred curd cheese. In study 1, heal times of 15, 22, and 29 min were used in manufacturing cheese. Curd was not healed or healed 15 or 30 min in study 2. Cooking curd immediately after cutting resulted in significantly lower moisture content in cheese, lower raw cheese yields, and higher fat loss into whey. Healing cheese curd 15 min or longer decreased syneresis, resulting in higher moisture cheese and increased raw cheese yield. Heal time extended to 30 min resulted in a significantly smaller loss of fat into whey. Healing time had a significant effect on moisture retention, fat loss, and raw cheese yield.     

From milk to cheese: Evolution of flavor fingerprint of milk,cream, curd,whey, ricotta,scotta, and ripened cheese obtained during summer Alpine pasture

The role of each step of cheese and ricotta making in development of flavor of cheese and other dairy products is not yet well known. The objectives of this study were to characterize volatile organic compounds (VOC) in cheese and ricotta making with bulk milk from cows grazing in a highland area and to evaluate their evolution in the various dairy products and by-products obtained during the production processes. A group of 148 cows was grazed day and night on pasture from June to September. A total of 7 cheese-making sessions were carried out using the bulk milk collected every 2 wk during summer pasturing according to the artisanal procedure used for Malga cheese production. All milks, products, and by-products were sampled, and the VOC content of milk, cream, whey, ricotta, scotta (residual liquid), fresh cheeses, and cheeses ripened for 6 and 12 mo was determined by solid-phase microextraction gas chromatography–mass spectrometry. Forty-nine compounds were identified belonging to the following chemical families: alcohols (13), aldehydes (9), esters (8), free fatty acids (6), ketones (5), lactones (2), sulfurs (2), terpenes (2), phenol (1), and benzene (1). The results showed that the amounts of VOC in the various dairy products differed significantly. Comparisons between the VOC of 4 types of milk (whole evening, skim evening, whole morning, mixed in the vat) showed that the skimming process had the greatest effect, with about half of all the VOC analyzed affected, followed by time of milking (evening milking vs. morning milking) and mixing (skim evening milk mixed with whole morning milk). In general, among fresh products, cream had higher contents of fatty acids, sulfurs, and terpene volatile compounds than fresh cheese and ricotta, whereas ricotta showed a very high VOC amount compared with fresh cheese, probably due to its high processing temperature. The effects of the progressive nutrient depletion in milk during processing were investigated by comparing the amounts of VOC in vat milk, whey, and scotta. Although milk contained greater amounts of nutrients, whey and especially scotta had higher concentrations of VOC, with the exception of esters, sulfurs, terpenes, and phenolic compounds, as a result of physicochemical and microbial modifications during processing. Finally, the effect of ripening was tested by comparing the VOC of fresh and ripened cheeses (6 and 12 mo), revealing that VOC release increased dramatically during the first semester and further with increasing the ripening period to 1 yr. In particular, some alcohols (butan-2-ol), aldehydes (2-methylpropanal, hexanal, and heptanal), esters (ethyl butanoate and ethyl hexanoate), fatty acids (acetic, butanoic, and hexanoic acids), and ketones (butan-2-one, pentan-2-one, and heptan-2-one) showed a very large increase. In conclusion, according to the artisanal milk processing carried out for Malga cheese production, the quantity of VOC was shown to increase about 3 times during cheese making (from milk in vat to fresh cheese plus whey), almost 4 times during ricotta making (from whey to ricotta plus scotta), and about 16 times during 1 yr of ripening of cheese.     

EFFECT OF FERMENTED WHEY PROTEIN CONCENTRATE ON TEXTURE OF IRANIAN WHITE CHEESE

The influence of fermented whey protein concentrate (FWPC) added before and after formation of cheese curd on the textural characteristics of Iranian white cheese was studied. The FWPC, prepared from whey obtained during cheese making, was added at different levels 5, 10, 15 and 20% (v/v) after (A) or before (B) cheese curdling. The changes in rheological parameters of cheeses were determined before and after 1 month of ripening. It was found that both incorporation level and stage of addition of FWPC (A and B) caused significant effects on texture profile analysis of cheeses. Increasing the level of FWPC in B group, except samples containing 10% FWPC, in contrast with A cheeses led to considerable increase in moisture and decrease in hardness and chewiness. Samples containing more than 15% FWPC had undesirable texture and were too soft. All experimental cheeses exhibited a decline in values for each rheological parameter after 1 month of ripening.

PRACTICAL APPLICATIONS

Perhaps the biggest story in the dairy industry in the past couple of decades has been the rise of new applications for whey and whey proteins. Once considered a waste product in the cheese manufacturing process, whey and whey protein products today are used for a wide range of functional and nutritional properties. In the cheese industry, particularly in soft cheese varieties, whey proteins have shown good applications to replace caseins as they act as fat replacer and bind more water than caseins, which results in softer cheeses. Therefore, this study was attempted to investigate the impact of fermented whey protein concentrate on textural attributes of Iranian white cheese.     

Elimination of the development of bitter flavour in Cheddar cheese made from milk containing heat-denatured whey protein

A method has been developed for increasing the yield of Cheddar cheese by as much as 7.5% by the incorporation of denatured whey protein in curd. The process effectively eliminates the development of intense bitter off-flavours which are generally associated with the production of cheese from acidified milk. Although the manufacturing procedure produces cheese with acceptable Cheddar flavour, the development of high quality Cheddar flavour is impaired