A nonlinear programming optimization model to maximize net revenue in cheese manufacture

A nonlinear programming optimization model was developed to maximize net revenue in cheese manufacture and is described in this paper. The model identifies the optimal mix of milk resources together with the types of cheeses and co-products that maximize net revenue. It works in Excel while it takes the data specified by the user from a user-friendly interface created in Access. The user can specify any number of resources, cheese types, and co-products. To demonstrate the capabilities of the model, we determined the impact of variation in milk price and composition in the period 1998 to 2000 on the optimal mix of resources and optimal type of co-product for Cheddar and low-moisture, part-skim Mozzarella. It was also desired to determine the impact of variation in protein content of nonfat dry milk (NDM) on net revenue, and examine the effect of reconstitution of NDM with water versus milk on net revenue. The optimal mix of resources and the net revenue markedly varied as milk resource prices and composition varied. The net revenue for Mozzarella was much higher than for Cheddar when the price of cream was high. Cheese plants that did not optimize the use of resources in response to variations in prices and composition missed a significant profit opportunity. Whey powder was more profitable than 34% whey protein concentrate and lactose in most months. The use of high-protein NDM led to an appreciable increase in net revenue. When the value of the nonfat portion of raw milk was high, reconstitution of NDM with water rather than milk markedly raised net revenue.     

Efficiency of removal of whey protein from sweet whey using polymeric microfiltration membranes

Our objective was to measure whey protein removal percentage from separated sweet whey using spiral-wound (SW) polymeric microfiltration (MF) membranes using a 3-stage, 3× process at 50°C and to compare the performance of polymeric membranes with ceramic membranes. Pasteurized, separated Cheddar cheese whey (1,080 kg) was microfiltered using a polymeric 0.3-μm polyvinylidene (PVDF) fluoride SW membrane and a 3×, 3-stage MF process. Cheese making and whey processing were replicated 3 times. There was no detectable level of lactoferrin and no intact α- or β-casein detected in the MF permeate from the 0.3-μm SW PVDF membranes used in this study. We found BSA and IgG in both the retentate and permeate. The β-lactoglobulin (β-LG) and α-lactalbumin (α-LA) partitioned between retentate and permeate, but β-LG passage through the membrane was retarded more than α-LA because the ratio of β-LG to α-LA was higher in the MF retentate than either in the sweet whey feed or the MF permeate. About 69% of the crude protein present in the pasteurized separated sweet whey was removed using a 3×, 3-stage, 0.3-μm SW PVDF MF process at 50°C compared with 0.1-μm ceramic graded permeability MF that removed about 85% of crude protein from sweet whey. The polymeric SW membranes used in this study achieve approximately 20% lower yield of whey protein isolate (WPI) and a 50% higher yield of whey protein phospholipid concentrate (WPPC) under the same MF processing conditions as ceramic MF membranes used in the comparison study. Total gross revenue from the sale of WPI plus WPPC produced with polymeric versus ceramic membranes is influenced by both the absolute market price for each product and the ratio of market price of these 2 products. The combination of the market price of WPPC versus WPI and the influence of difference in yield of WPPC and WPI produced with polymeric versus ceramic membranes yielded a price ratio of WPPC versus WPI of 0.556 as the cross over point that determined which membrane type achieves higher total gross revenue return from production of these 2 products from separated sweet whey. A complete economic engineering study comparison of the WPI and WPPC manufacturing costs for polymeric versus ceramic MF membranes is needed to determine the effect of membrane material selection on long-term processing costs, which will affect net revenue and profit when the same quantity of sweet whey is processed under various market price conditions.     

Effect of incorporation of denatured whey protein on the yield and quality of Cheddar cheese

Concentrated suspensions of a denatured protein-fat complex were prepared by centrifugation of whey which had been heated in acid conditions. Significant improvements in cheese yield were obtained on adding the concentrate to milk for cheesemaking before renneting. A maximum increase in yield of 7% was attained in manufacturing Cheddar cheese which satisfied the legal requirements for moisture content. No consistent texture or flavour defects were evident in the cheese during the first jive months of maturation.     

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.     

High Pressure Treatment of Milk and Effects on Microbiological and Sensory Quality of Cheddar Cheese

The effect of cycled high pressure treatment of milk on the yield, sensory, and microbiological quality of Cheddar cheese was investigated. Cheddar cheeses were made from pasteurized, raw, or pressure treated milk according to traditional methods. Flavor scores from trained dairy judges were not different for pasteurized and pressurized milk cheeses (P≤0.05). Percent moisture and wet weight yields of pressure treated milk cheeses were higher than pasteurized or raw milk cheeses (P≤0.05). Microbiological quality of pressurized milk cheeses was comparable to pasteurized milk cheeses. Texture defects were present in pressurized milk cheeses and were attributed to excess moisture. High pressure treatment of milk shows promise as an alternative to heat pasteurization prior to cheesemaking.     

Influence of Production and Prices on Optimum Culling Rates and Annualized Net Revenue

Dynamic programming was used to make optimum insemination and culling decisions for a dairy enterprise. Monthly costs and revenues for cows were calculated from milk and fat yields, calf values, feed costs, veterinary costs, housing and equipment costs, and interest. Cows were described in the dynamic programming model by lactation number, month in lactation, milk production during the present and previous lactations, and time of conception. The model considered variation in milk yield, replacement heifer costs, carcass values, involuntary culling, genetic improvement, conception rates, semen costs, and interest. Prices and parameters were chosen to represent the Holstein population in the US. Optimum average yearly culling rate was about 25% (optimum average herd life was 47.8 mo) and the yearly annuity of net revenue for a replacement heifer over a 15-yr planning horizon was $443 in the base situation. Various average mature equivalent yields, replacement heifer prices, milk prices, and feed prices were used in a sensitivity analysis. The yearly annuity of net revenue was sensitive to changes in all these parameters. Milk yield, milk prices, and feed prices had major effects on yearly annuity. Optimum culling decisions were sensitive to changes in replacement heifer prices. Average mature equivalent milk yield, milk price, and feed price had small effects on culling.     

A comparison of the composition, coagulation characteristics and cheesemaking capacity of milk from Friesian and Jersey dairy cows

Twenty-nine multiparous cows of each of the Jersey and Friesian breeds, all kappa-casein AB phenotype, were grazed together and managed identically. On three occasions during 10 d in spring (early lactation), milk was collected from all cows at four consecutive milkings and bulked according to breed. On a separate occasion, milk samples were also collected from each cow at consecutive a.m. and p.m. milkings to form one daily sample per cow. The bulked milks (800-1000 l per breed on each occasion) were standardized to a protein:fat (P:F) ratio of 0.80, and 350 l from each breed was made into Cheddar cheese. The solids content of the remaining Friesian milk was then increased by ultrafiltration to a solids concentration equal to that of the Jersey milk. This solids-standardized Friesian milk and a replicate batch of P:F standardized Jersey milk were made into two further batches of Cheddar cheese in 350-l vats. Compared with Friesian milk, Jersey milk had higher concentrations of most milk components measured, including protein, casein and fat. There were few difference in milk protein composition between breeds, but there were differences in fat composition. Friesian milk fat had more conjugated linoleic acid (CLA) than Jersey milk fat. Jersey milk coagulated faster and formed firmer curd than Friesian milk. Concentrations of some milk components were correlated with coagulation parameters, but relationships did not allow prediction of cheesemaking potential. Jersey milk yielded 10% more cheese per kg than Friesian milk using P:F standardized milk, but for milks with the same solids concentration there were no differences in cheese yield. No differences in cheese composition between breeds were detected. Differences in cheesemaking properties of milk from Jerseys and Friesians were entirely related to the concentrations of solids in the original milk.     

Fortification of cheese with vitamin D(3) using dairy protein emulsions as delivery systems

Vitamin D is an essential vitamin that is synthesized when the body is exposed to sunlight or after the consumption of fortified foods and supplements. The purpose of this research was to increase the retention of vitamin D(3) in Cheddar cheese by incorporating it as part of an oil-in-water emulsion using a milk protein emulsifier to obtain a fortification level of 280 IU/serving. Four oil-in-water vitamin D emulsions were made using sodium caseinate, calcium caseinate, nonfat dry milk (NDM), or whey protein. These emulsions were used to fortify milk, and the retention of vitamin D(3) in cheese curd in a model cheesemaking system was calculated. A nonemulsified vitamin D(3) oil was used as a control to fortify milk. Significantly more vitamin D(3) was retained in the curd when using the emulsified vitamin D(3) than the nonemulsified vitamin D(3) oil (control). No significant differences were observed in the retention of vitamin D(3) when emulsions were formulated with different emulsifiers. Mean vitamin D(3) retention in the model system cheese curd was 96% when the emulsions were added to either whole or skim milk compared with using the nonemulsified oil, which gave mean retentions of only 71% and 64% when added to whole and skim milk, respectively. A similar improvement in retention was achieved when cheese was made from whole and reduced-fat milk using standard manufacturing procedures on a small scale. When sufficient vitamin D(3) was added to produce cheese containing a target level of approximately 280 IU per 28-g serving, retention was greater when the vitamin D(3) was emulsified with NDM than when using nonemulsified vitamin D(3) oil. Only 58±3% of the nonemulsified vitamin D(3) oil was retained in full-fat Cheddar cheese, whereas 78±8% and 74±1% were retained when using the vitamin D(3) emulsion in full-fat and reduced-fat Cheddar cheese, respectively.     

Impact of low concentration factor microfiltration on the composition and aging of Cheddar cheese

The effect of microfiltration (MF) on proteolysis, hardness, and flavor of Cheddar cheese during 6 mo of aging was determined. Raw skim milk was microfiltered two-fold in two cheese making trials. In trial 1, four vats of cheese were made in 1 d using unconcentrated milk (1X), 1.26X, 1.51X, and 1.82X concentration factors (CF). Casein-(CN)-to-fat ratio was constant among treatments. Proteolysis during cheese aging decreased with increasing CF due to either limitation of substrate availability for chymosin due to low moisture in the nonfat substance (MNFS), inhibition of chymosin activity by high molecular weight milk serum proteins, such as alpha2-macroglobulin, retained in the cheese or low residual chymosin in the cheese. Hardness of fresh cheese increased, and cheese flavor intensity decreased with increasing CF. In trial 2, the 1X and 1.8X CF were compared directly. Changes made in the cheese making procedure for the 1.8X CF (more chymosin and less cooking) increased the MNFS and made proteolysis during aging more comparable for the 1X and 1.8X cheeses. The significant difference in cheese hardness due to CF in trial 1 was eliminated in trial 2. In a triangle test, panelists could not differentiate between the 1X and 1.8X cheeses. Therefore, increasing chymosin and making the composition of the two cheeses more similar allowed production of aged Cheddar cheese from milk concentrated up to 1.8X by MF that was not perceived as different from aged Cheddar cheese produced without MF.     

DIRECT VAT INOCULATION OF MILK WITH FREEZE-DRIED STARTERS FOR MAKING CHEDDAR CHEESE

The introduction of cheese starter developed by Vitex, Paris, France, in concentrated, freeze-dried form for direct inoculation of milk in the cheesemaking vat offers considerable advantages and the performance of some ICF starters (Inoculum pour Cuve de Fabrication) for making Cheddar is reported. Conditions regarding level of inocula and processing temperatures to establish satisfactory curd making in an acceptable making time are described and numbers of starter bacteria in the milk and in the curd at pressing and the pattern of acidity development during processing are shown to be very similar to those in standard control Cheddar cheesemaking with liquid starter cultures. No apparent lag-phase was observed in the production of acidity by these freeze-dried starters. Chemical analysis and official grading of the cheeses showed them to be of good quality.     

A comparison of cheese yield and cheesemaking efficiency using seasonal and standardized milk

A study has been carried out on the efficiency of the cheesemaking process when Cheddar cheese was made from milk showing the normal seasonal trends in composition and from milk that had been standardized to a crude protein: fat ratio of 0.9. Standardization resulted in a small loss of yield from a standard volume of milk (averaged over a complete year), but this loss was compensated by an almost equal gain in the efficiency of fat retention.     

Evaluation of Thiol Activated Proteases from Clam Viscera as a Rennet Substitute for Cheese-Making

Clam rennet, which is a crude enzyme preparation of cathepsin B-like protease from clam viscera was characterized and compared to porcine pepsin and calf rennet for its suitability as a milk coagulant in cheesemaking. Clam rennet was more proteolytic and produced a softer curd than the other two coagulants. However, influences of the pH and temperature on milk clotting with clam rennet were very similar to those of calf rennet. The cheddar cheese made from clam rennet was not inferior to the Cheddar cheese made from calf rennet. Quality enhancement occurred despite the view that high ratio of proteolytic to clotting activity is generally considered to be unfavorable for cheese-making. The higher proteolytic activity appeared to accelerate the ripening process. A small yield loss occurred as a result of excessive proteolysis during cheese-making.     

Yield of Cheddar cheese manufactured from milk concentrate by ultrafiltration

There are basically two methods by which the manufacture of cheese from milk concentrated by ultrafiltration can increase yields. Firstly, the procedure can increase the weight of certain water-soluble, solids-non-fat components (mainly whey proteins) in the cheese. This extra solids-non-fat may allow extra water to be incorporated into the product without a decline in quality. Secondly, if suitable equipment can be designed, manufacture of cheese from concentrated milk can lead to a reduction in the losses of insoluble casein, fat and fines. The present study suggests that with a fivefold concentration of milk by ultrafiltration, and with the same losses of insoluble casein, fat and fines as with conventional cheesemaking, the yield of Cheddar is increased by around 4.5%. About half this increase is due to water-soluble, solids-non-fat components; the remainder is due to water. With the elimination of all losses of insoluble casein and fines the gain in product is predicted to be around 6% while increases in the fat retention to 95% would bring the yield advantage to about 8%. However, it is suggested that the elimination of casein fines losses may be difficult to achieve in commercial-scale, ultrafiltration cheesemaking equipment and that reductions in fat percentages in the whey are of little financial advantage to companies that recover whey fat .     

Standardisation of milk for cheesemaking at factory level

The percentage of milk fat recovered as cheese varies between 85 and 93 per cent, depending on the system used, and this must be taken into account when the casein to fat ratio of milk for cheesemaking is selected. Seasonal variation in the composition of milk protein can have a significant influence on the potential cheese yield. Prolonged storage of milk may cause casein losses while heat precipitation can facilitate the incorporation of whey proteins in cheese curd. The economic consequences of seasonal variations in Ireland on the price of milk for cheesemaking are discussed. The economics of standardisation may be marginal, but it is a useful aid in achieving uniform cheese quality.     

Valuation of milk composition and genotype in cheddar cheese production using an optimization model of cheese and whey production

A mass balance optimization model was developed to determine the value of the κ-casein genotype and milk composition in Cheddar cheese and whey production. Inputs were milk, nonfat dry milk, cream, condensed skim milk, and starter and salt. The products produced were Cheddar cheese, fat-reduced whey, cream, whey cream, casein fines, demineralized whey, 34% dried whey protein, 80% dried whey protein, lactose powder, and cow feed. The costs and prices used were based on market data from March 2004 and affected the results. Inputs were separated into components consisting of whey protein, ash, casein, fat, water, and lactose and were then distributed to products through specific constraints and retention equations. A unique 2-step optimization procedure was developed to ensure that the final composition of fat-reduced whey was correct. The model was evaluated for milk compositions ranging from 1.62 to 3.59% casein, 0.41 to 1.14% whey protein, 1.89 to 5.97% fat, and 4.06 to 5.64% lactose. The κ casein genotype was represented by different retentions of milk components in Cheddar cheese and ranged from 0.715 to 0.7411 kg of casein in cheese/kg of casein in milk and from 0.7795 to 0.9210 kg of fat in cheese/kg of fat in milk. Milk composition had a greater effect on Cheddar cheese production and profit than did genotype. Cheese production was significantly different and ranged from 9,846 kg with a high-casein milk composition to 6,834 kg with a high-fat milk composition per 100,000 kg of milk. Profit (per 100,000 kg of milk) was significantly different, ranging from $70,586 for a high-fat milk composition to $16,490 for a low-fat milk composition. However, cheese production was not significantly different, and profit was significant only for the lowest profit ($40,602) with the κ-casein genotype. Results from this model analysis showed that the optimization model is useful for determining costs and prices for cheese plant inputs and products, and that it can be used to evaluate the economic value of milk components to optimize cheese plant profits.     

Diversity of traditional Caciocavallo cheeses produced in Italy

This paper presents the results of a survey carried out in 68 dairies in southern Italy on the manufacturing processes of traditional Italian Caciocavallo cheese varieties. Following a study of the relevant literature, the various cheesemaking processes were analysed and the implications of different cheesemaking procedures were explored. The manufacturing variations able to influence the organoleptic characteristics of Caciocavallo cheese were milk and rennet types, procedures for curd acidification and stretching, salting and ripening conditions, and smoking treatment. This survey is designed to guide producers and consumers alike with respect to the perceivable effects of manufacturing variants on cheese quality.     

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     

Prediction of moisture in cheese of commercial production using neural networks

Control of cheese moisture is paramount to maximizing yield and profitability of a cheesemaking operation. Modeling and prediction of cheese moisture prior to pressing from a large industrial database for stirred-curd Cheddar cheese made with non-standardized and standardized milk was carried out using neural networks (NN). The number of model input variables was reduced by removing or combining some of them, based on cheesemaking knowledge and on the results of two tests estimating the impact of each model input. Input removal was carried out until the validation mean absolute prediction error (MAPE) increased. An initial NN cheese moisture model with 38 input process variables, coded as 57 NN inputs, was reduced to one with 21 input process variables, coded as 34 NN inputs. For the latter, the validation MAPE was 0.53% cheese moisture in a range of cheese moisture of 13.2%, and 0.51% for the best 25% of models (out of 100). For the range of operating conditions of the process in this study, four main groups of variables were found to be the most influential on the prediction of cheese moisture: cutting and subsequent stirring of the curd, curd rinsing temperature, starter quantity, activity and strain, and seasonal variation of milk composition. The NN model with the selected input variables and optimized number of hidden neurons was then used to predict cheese moisture for ranges of these variables. This study showed that NN models can successfully extract input–output variable relationships from industrial production data in spite of the inherent error in these data. The resulting NN models can be used both for research to develop the base of knowledge on production variables and their complex interactions, as well as for the prediction of cheese moisture.     

Applicability of a bacteriocin-producing Enterococcus faecium as a co-culture in Cheddar cheese manufacture

Two strains, Enterococcus faecium RZS C5 and E. faecium DPC 1146, produce listericidal bacteriocins, so-called enterocins. E. faecium RZS C5 was studied during batch fermentation in both a complex medium (MRS) and in milk to understand the influence of environmental factors, characteristic for milk and cheese, on both growth and bacteriocin production. Fermentation conditions were chosen in view of the applicability of in situ enterocin production during Cheddar cheese production. Enterocin production by E. faecium RZS C5 in MRS started in the early logarithmic growth phase, and enterocin activity decreased during the stationary phase. The effect of pH on enterocin production and decrease of activity was as intense as the effect on bacterial growth. Higher enterocin production took place at pH 5.5 compared with pH 6.5. The use of lactose instead of glucose increased the production of enterocin, and at higher lactose concentration, production increased more and loss of activity decreased. The production in skimmed milk compared to MRS was lower and was detected mainly in the stationary phase. When casein hydrolysate was added to the milk, enterocin production was higher and started earlier, indicating the importance of an additional nitrogen source for growth of E. faecium in milk. For co-cultures of E. faecium RZS C5 with the starters used during Cheddar cheese manufacture, no enterocin activity was detected during the milk fermentation. Furthermore, the applicability of E. faecium RZS C5 and E. faecium DPC 1146 strains was tested in Cheddar cheese manufacture on pilot scale. Enterocin production took place from the beginning of the cheese manufacturing and was stable during the whole ripening phase of the cheese. This indicates that both an early and late contamination of the milk or cheese can be combated with a stable, in situ enterocin production. The use of such a co-culture is an additional safety provision beyond good manufacturing practices.     

Whole Milk Reverse Osmosis Retentates for Cheddar Cheese Manufacture: Cheese Composition and Yield

The impact of concentrating whole milk by reverse osmosis prior to Cheddar cheese making was studied. Heat treated, standardized, whole milk was reduced in volume by 0, 5, 10, 15, and 20% prior to Cheddar cheese manufacture. Milk solids at various milk volume reductions were 11.98, 12.88, 13.27, 14.17, and 15.05%, respectively. Permeates contained only traces of organic matter and would not create a significant by-product handling problem for a cheese plant. Solids content of the whey from cheese making increased with increasing milk concentration. Proximate compositions of reverse osmosis cheeses were comparable to control cheeses. Fat losses decreased, and fat retained in the cheese increased with increasing milk solids concentration. Improved fat recovery in the cheese was related to the amount of mechanical homogenization of milk fat during the concentration process. Actual, composition adjusted, and theoretical cheese yields were determined. Increased retention of whey solids and improved fat recovery gave cheese yield increases of 2 to 3% above expected theoretical yields at 20% milk volume reduction. Water removal from whole milk prior to Cheddar cheese manufacture gave increased productivity and cheese yield without requiring different cheese-making equipment or manufacturing procedures.