The effect of calcium chloride addition on the microstructure and composition of Cheddar cheese

The addition of calcium is widely accepted as a tool in cheese-making but the effect on the microstructure of cheese during and following manufacture is not known. In this study, cheeses made with milk containing 200–600 mg L⁻¹ of additional CaCl₂ had significantly lower fat loss into the whey collected after cooking; however, the final fat composition or yield of cheese did not change. The microstructure of the gel with 300 or 600 mg L⁻¹ CaCl₂ addition was less porous and the cooked curd consisted of a denser protein network that may retain more fat during the early stages of manufacture. In contrast, the cheddared curd and cheese contained more micro-pores than cheeses with lower or no calcium addition. Such micro-pores could possibly be the channels by which fat escaped during pressing. This study shows that calcium addition altered the microstructure and pattern of fat loss during Cheddar manufacture.     

Influence of sucrose on cold gelation of heat‐denatured whey protein isolate

A solution of heat‐denatured whey proteins was prepared by heating 100 g kg⁻¹ whey protein isolate (WPI) at pH 7.0 to 75 °C for 15 min in the absence of salt. Heat treatment caused the globular protein molecules to unfold, but electrostatic repulsion opposed strong protein–protein aggregation and so prevented gel formation. When the heat‐denatured whey protein solution was cooled to room temperature and mixed with 15 mM CaCl₂, it formed a gel. We investigated the influence of the presence of sucrose in the protein solutions prior to CaCl₂ addition on the gelation rate. At relatively low concentrations (0–100 g kg⁻¹), sucrose decreased the gelation rate, presumably because sucrose increased the aqueous phase viscosity. At higher concentrations (100–300 g kg⁻¹), sucrose decreased the gelation rate, probably because sugar competes for the water of hydration and therefore increases the attraction between proteins. These data have important implications for the application of cold‐setting WPI ingredients in sweetened food products such as desserts. © 2000 Society of Chemical Industry     

Caffeine-loaded whey protein hydrogels reinforced with gellan and enriched with calcium chloride

Gellan gum and CaCl₂ were exploited to modulate the textural and techno-functional properties of heat-set whey protein hydrogels. Enrichment with CaCl₂ increased the amount of released caffeine from the protein hydrogel in conjunction with decreasing cohesiveness index and microstructural features modification. Gellan bundles as visualised by microscopic images conferred a remarkable reinforcing influence to gel samples; enrichment with gellan at 0.5 mg mL⁻¹ increased the gel hardness value approximately 6.4 fold. Based on Fourier transform infrared (FTIR) spectroscopy it was suggested that gellan and CaCl₂ enrichments decreased the β-sheet content of the protein gel matrix in favour of random coil structures. FTIR spectroscopy also proposed cation-π interactions between Ca²⁺ ions and electron-rich amide bonds of whey proteins, as well as interactions between carboxyl groups of gellan and the ε-amino group of lysine in β-lactoglobulin.     

A feasibility study on the pilot scale manufacture of fresh cheese from skim milk retentates without acid whey production: Effect of calcium content on bitterness and texture

The sensory and structural properties of fresh cheeses (8.0%, w/w, protein) made from fermented skim milk retentates [concentrated-fermented (CoF) fresh cheese] with different calcium-protein ratios (Ca:Prot; 15.9–36.6 mg g⁻¹) by means of pilot plant scale microfiltration (MF) and MF in the diafiltration (DF) mode without acid whey (AW) production were characterised. Calcium reduction reduced the bitterness level significantly (by 53.4%) and the bitter peptide content (by ≈33%) of the CoF fresh cheese after ≤ 1 week of storage; however, storage for ≥ 2 weeks resulted in an increase of both bitterness and bitter peptide content, and quantitatively changed the peptide pattern, possibly due to lack of thermisation. Fresh cheese with a lower bitterness level can be successfully manufactured, while avoiding AW production, if the Ca:Prot of the milk retentate is decreased to ≤15.9 mg g⁻¹ (calcium content = 1240 mg kg⁻¹ at 7.81%, w/w, protein) prior to fermentation.     

Antinociceptive and anti-inflammatory effects of novel dietary protein hydrolysate produced from whey by proteases of Cynara cardunculus

Antinociceptive and anti-inflammatory effects of a peptide concentrate mix (PepC) obtained from whey protein, via hydrolysis with cardosins from Cynara cardunculus, was tested in vivo. The antinociceptive effect was assessed using writhing, hot-plate and formalin tests in mice, and the anti-inflammatory effect using the paw oedema test. PepC at 300 mg kg⁻¹ bw conveyed a significant result in the writhing test when co-administered with 1 and 3 mg kg⁻¹ bw indomethacin, similar to administration of higher doses of indomethacin alone. Conversely, no statistically significant differences were observed in the paw oedema test when the same PepC concentration was co-administered with dexamethasone at 3, 10 and 30 mg kg⁻¹ bw. PepC at 1000 mg kg⁻¹ bw did not cause any remarkable outcome in the hot-plate test. PepC appears to possess anti-inflammatory and peripheral antinociceptive activities, so it may be a candidate for nutraceutical ingredient.     

Calcium and chitosan-mediated clustering of whey protein particles for tuning their colloidal stability and flow behaviour

Whey protein microgel (WPM) particles were prepared by heating whey protein dispersions (40 mg mL⁻¹) at pH 5.8 and 80 °C for 15 min. Supplementation with 5 mm CaCl₂ at pH 6.0 increased the hydrodynamic diameter of WPMs, but did not influence the ζ-potential of the particles. The latter was attributed to clustering of WPMs by Ca²⁺ bridges. Supplementing WPM suspension with chitosan (0.5 mg mL⁻¹) at pH 5.0 caused formation of micron-sized clusters and a progressive increase in suspension viscosity over the subsequent 48 h. The latter was ascribed to development of a complexed lattice that inhibited sedimentation of WPMs. Immediately after chitosan supplementation, the WPM suspension changed from Newtonian to shear-thinning fluid. Fourier transform infra-red spectroscopy results suggested that microgelation proceeded by formation of inter-molecular β-sheets and loss of α-helix structure. It also indicated that chitosan may interact with WPMs at pH 6.0 through its acetyl groups.     

Visible-near infrared spectroscopy sensor for predicting curd and whey composition during cheese processing

The potential of visible-near infrared spectra, obtained using a light backscatter sensor, in conjunction with chemometrics, to predict curd moisture and whey fat content in a cheese vat was examined. A three-factor (renneting temperature, calcium chloride, cutting time), central composite design was carried out in triplicate. Spectra (300–1,100 nm) of the product in the cheese vat were captured during syneresis using a prototype light backscatter sensor. Stirring followed upon cutting the gel, and samples of curd and whey were removed at 10 min intervals and analyzed for curd moisture and whey fat content. Spectral data were used to develop models for predicting curd moisture and whey fat contents using partial least squares regression. Subjecting the spectral data set to Jack-knifing improved the accuracy of the models. The whey fat models (R = 0.91, 0.95) and curd moisture model (R = 0.86, 0.89) provided good and approximate predictions, respectively. Visible-near infrared spectroscopy was found to have potential for the prediction of important syneresis indices in stirred cheese vats.     

Impact of milk preacidification with CO2 on cheddar cheese composition and yield

Preacidification of milk for cheese making may have a beneficial impact on increasing proteolysis during cheese aging. Unlike other acids, CO(2) can easily be removed from whey. The objectives of this work were to determine the effect of milk preacidification on Cheddar cheese composition, the recovery of individual milk components, and yield. Carbon dioxide was injected inline after the cooling section of the pasteurizer. Cheeses with and without added CO(2) were made simultaneously from the same batch of milk. This procedure was replicated 3 times. Carbon dioxide in the cheese milk was about 1600 ppm, which resulted in a milk pH of about 5.9 at 31 degrees C. The starter culture and coagulant addition rates were the same for both the CO(2) treatment and the control. The whey pH at draining of the CO(2) treatment was lower than the control. Total make time was shorter for the CO(2) treatment compared with the control. Cheese manufactured from milk acidified with CO(2) retained less of the total calcium and fat than the control cheese. The higher fat loss was primarily in the whey at draining. Preacidification with CO(2) did not alter the crude protein recovery in the cheese. The CO(2) treatment resulted in a higher added salt recovery in the cheese and produced a cheese that contained too much salt. Considering the higher added salt retention, the salt application rate could be lowered to achieve a typical cheese salt content. Cheese yield efficiency of the CO(2) treated milk was 4.4% lower than the control due to fat loss. Future work will focus on modifying the make procedure to achieve a normal fat loss into the whey when CO(2) is added to milk.     

Isolation of bovine serum albumin from whey using affinity chromatography

The adsorption of bovine serum albumin (BSA) to a chromatography resin with immobilised llama antibody fragments as affinity ligands was investigated. The maximum adsorption capacity of the affinity resin was 21.6 mg mL⁻¹ with a Langmuir equilibrium constant of 20.4 mg mg⁻¹. Using packed bed chromatography, BSA was adsorbed from pure BSA solutions. Recovery was achieved by desorption at pH 3. In experiments with initial BSA concentrations of 1 mg mL⁻¹ and 0.1 mg mL⁻¹, BSA could be concentrated to 6.9 and 7.7 mg mL⁻¹, respectively. BSA was also isolated from filtered bovine cheese whey containing less than 0.1 mg mL⁻¹ BSA. The purified BSA was in this case concentrated to 7.4 mg mL⁻¹ BSA. The presence of other components in the feedstock did not alter the adsorption capacity of the affinity resin. The results show that high recovery combined with high purity can be obtained using affinity chromatography.     

Economic aspects of cheese making as influenced by whey processing options

Economic consequences of the cheese making process are illustrated through several sample calculations concerning processing of whey in relation to cheese making throughput and several whey processing alternatives. Small cheese plants with daily milk throughput of approximately 100 000 kg cannot economically justify the capital for water removal equipment. For small plants that have to convert whey to a dry product, alternatives include pre-concentrating with a reverse osmosis unit or a small plate evaporator and drying on a double roller dryer. The economics are evaluated at several price levels. At the upper scale of cheese plant size (2–3 million kg d⁻¹ of milk), the investment for whey processing is about half the total investment. Cash flows are calculated for electricity, natural gas and whey powder prices. Increased investment for further processing into whey protein concentrate and dried whey solubles or lactose is evaluated at several price levels.     

Effect of commercial adjunct cultures on proteolysis in low-fat Kefalograviera-type cheese

The effect of two commercially available adjunct cultures, LBC 80 (Lactobacillus casei subsp. rhamnosus) and CR-213 (containing Lactococcus lactis subsp. cremoris and Lc. lactis subsp. lactis) on the proteolysis in low-fat hard ewes’ milk cheese of Kefalograviera-type was investigated. Two controls, a full-fat cheese (306 g kg⁻¹ fat, 378 g kg⁻¹ moisture) and a low-fat cheese (97 g kg⁻¹ fat, 486 g kg⁻¹ moisture, made using a modified procedure), were also prepared. The effect of adjunct culture on proteolysis, as examined by polyacrylamide gel electrophoresis of cheese and water soluble cheese extracts, was marginal. The reverse-phase HPLC peptide profiles of the water soluble extracts from low-fat cheeses were similar although some quantitative differences were observed between low-fat control cheese and experimental cheeses. The fat content as reflected by the differences in peptide profiles affected the pattern of proteolysis. Proteolysis, as measured by the percentage of total nitrogen soluble in water or in 120 g L⁻¹ trichloroacetic acid, was significantly (P<0.05) affected by the addition of adjunct cultures. Furthermore, the adjunct cultures enhanced the production of low molecular mass nitrogenous compounds; the levels of total nitrogen, soluble in 50 g L⁻¹ phosphotungstic acid, and of free amino acids were significantly (P<0.05) higher in the low-fat experimental cheeses than in the low-fat control cheese.     

The effect of fat content on the rheology,microstructure and heat-induced functional characteristics of Cheddar cheese

Cheddar cheeses with the different fat contents were made in triplicate and ripened at 4°C for 30 d and at 7°C for the remainder of the 180-d investigation period. The cheeses were designated: full-fat (FFC), 300 g kg⁻¹; reduced-fat (RFC), 219 g kg⁻¹; half-fat (HFC), 172 g kg⁻¹; and low-fat (LFC), 71.5 g kg⁻¹. A decrease in the fat content from 300 to ≤172 g kg⁻¹ resulted in significant (P<0.05) decreases in contents of moisture in non-fat substance and pH 4.6 soluble N (expressed as % total N), and increases in the contents of moisture, protein, intact casein and free amino acids. Reduction in fat content resulted in an increase in the volume fraction of the casein matrix and a decrease in the extent of fat globule clumping and coalescence. The mean values of fracture stress and firmness for the FFC were significantly lower than those of the RFC and HFC, which had similar values; the values for the LFC exceeded the limits of the test and were markedly higher than those of the other cheeses at all times. On baking the cheese, reduction in fat content resulted in significant increases in the mean melt time (time required for shred fusion) and apparent viscosity and a decrease in the mean flowability of the melted cheese. The stretchability of the FFC increased most rapidly and, at ∼15 and 30 d, attaining mean values which were significantly higher than those of the other cheeses. Thereafter the stretchability of the FFC decreased progressively to values that were significantly (i.e. at 150 d) or numerically (i.e., at 180 d) lower than those of the RFC and HFC. At ripening times ≥15 and ≤90 d, the stretchability of the LFC was significantly lower than that of the RFC, and significantly or numerically lower than the HFC.     

Base-line susceptibility of field populations of Rhyzopertha dominica (F.) to spinosad in Australia

Spinosad has recently been registered in several countries for long-term protection against a range of stored grain insects including the lesser grain borer, Rhyzopertha dominica (F.). The potential for development of resistance to spinosad is demonstrated by the existence of resistance in many insect pests of agriculture. The aim of this study was to determine the base-line susceptibility of R. dominica to spinosad, to provide a basis for future resistance monitoring. Eighteen insect populations of R. dominica were collected from field storage sites across four States within Australia, and exposed to a range of spinosad rates, including its current registered rate of 1 mg kg⁻¹ (1 ppm). Base-line susceptibility was assessed based on adult mortality and production of F₁ adults. Comparison of LC₅₀ and LC_99.9 indicated the existence of low level of variation among the tested R. dominica populations, in their susceptibility to spinosad. For adults, there was a narrow range of LC₅₀ values with the highest (0.027 ppm) being 2.5 × the lowest (0.011 mg kg⁻¹). Similarly, LC_99.9 values showed a narrow range with the highest (0.36 mg kg⁻¹) being 3.6 × the lowest (0.10 mg kg⁻¹). For adult progeny produced in spinosad treated grain, there was a narrow range of LC₅₀ values with the highest (0.025 mg kg⁻¹) being 5 × the lowest (0.004 mg kg⁻¹) and the highest LC_99.9 values (0.67 mg kg⁻¹) being 5 × the lowest LC_99.9 (0.13 mg kg⁻¹). Based on the data generated from this study, we recommend a dose of 1 mg kg⁻¹(1 ppm) to be used to discriminate between susceptible and resistant populations for future resistance monitoring programs.     

Selenium supplementation of diets of dairy cows to produce Se-enriched cheese

Selenium (Se) deficiency in people and animals is a nutritional problem in many regions of the world. Ten mid-lactation Estonian Red dairy cows were supplemented for 64 days with inorganic Se [0.39 mg kg⁻¹ in total mixed ration (TMR)] followed by a 57-day period of supplementation with organic and inorganic Se (0.44 mg kg⁻¹ in TMR), according to EU directives on maximum allowed amounts. Feeding organic Se increased Se content in blood (from 186.5 to 287.9 μg kg⁻¹), milk (from 17.1 to 51.8 μg kg⁻¹) and Edam-type cheese made there from (from 146 to 361 μg kg⁻¹). Se content in milk after supplementation was high enough to produce a cheese enabling the nutrition claim “high in Se” and related health claims. The concentration of the main primary oxidation products of linoleic acid (oxylipins) was low and leukotoxin diols were found in trace amounts; the oxidative stability of cheeses was high.     

Determination of menaquinone production by Lactococcus spp. and propionibacteria in cheese

Two genera of lactic acid bacteria are principally known to produce menaquinones in cheese: Lactococcus spp. in semi-hard cheese such as Vacherin Fribourgeois and Raclette, and propionibacteria in Swiss-type cheese such as Emmental. Menaquinone (MK) content of several cheese loaves was analysed to determine the impact of sampling site, ripening time and cultures used during cheese making. With Lactococcus spp., in Vacherin and in Raclette, the principal menaquinone was MK-9 (median = 149 μg kg⁻¹ and median = 167 μg kg⁻¹) followed by MK-8 (median = 70 μg kg⁻¹ and median = 66 μg kg⁻¹). In Emmental cheese, the principal menaquinone was MK-4 (median = 48 μg kg⁻¹) in young cheese and MK-9(4H) (median = 468 μg kg⁻¹) in cheese older than 90 days. The only difference in sampling site was found in Raclette for MK-9. In Vacherin, MK-8, MK-9 and total contents of menaquinones were significantly different according to the strain of Lactococcus lactis ssp. cremoris used.     

Rheological methods to analyse the thermal aggregation of calcium enriched milks

The colloidal state of calcium enriched milks during heating and its microstructures were analysed through interpretation of rheometric data with the Brownian aggregation theory, which can be considered as complementary to the methods currently used. Viscosity was measured at 100 s⁻¹ through temperature and time sweeps. It was observed that from 25 to 60 °C, viscosity slowly decreased as temperature increased; above 60 °C, viscosity sharply increased at different temperatures depending on the amount of CaCl₂. From time sweeps, the aggregation of casein micelles was described through the Smoluchowski theory. The addition of CaCl₂ at concentrations of 20–30 mmol kg⁻¹ decreased the stability factor 5 to 6 orders of magnitude compared with non-enriched milk. Values of the fractal dimension indicated that aggregation yields disordered aggregates occluding high amounts of solvent. The methodology described may help to analyse colloidal stability and structures when different calcium salts are used for enrichment.     

Impact of divalent salts and bovine gelatin on gel properties of phosphorylated gelatin from the skin of unicorn leatherjacket

The impact of zinc chloride (ZnCl₂) and calcium chloride (CaCl₂) as well as bovine gelatin (BG) on the gel strength of phosphorylated fish gelatin (PFG) from the skin of unicorn leatherjacket was investigated. The gel strength of PFG increased with increasing concentrations of ZnCl₂ and CaCl₂ (2.5–40 μmol L⁻¹). A higher gel strength was observed with CaCl₂, compared with ZnCl₂. The gel strength of PFG with 20 μmol L⁻¹ CaCl₂ increased by 15.7%, compared to the control gel. Nevertheless, at higher concentration (40 μmol L⁻¹) of both salts, gel strength of PFG decreased. Hardness of gels decreased with increasing PFG content (P < 0.05). Nevertheless, no differences in hardness were found amongst gels with BG/PFG ratios of 4:0 and 3:1 (P ≥ 0.05). Thus, PFG could be used in combination with CaCl₂ to substitute for BG at a level of 25%.     

Rapid analysis of magnesium in infant formula powder using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was investigated to determine magnesium (Mg) content in infant formula powder. To predict Mg content in the range established by the Codex Alimentarius, a partial least squares regression (PLSR) model was developed using a calibration data set (n = 30) based on full cross-validation and validated using an independent validation data set (n = 21). The prediction model performance was evaluated using the regression coefficients of determination (R_cv² = 0.94 and R_p² = 0.85) with the root mean square errors on cross-validation and prediction (RMSECV = 60 mg kg⁻¹ and RMSEP = 80 mg kg⁻¹). The limit of detection (150 mg kg⁻¹) was also calculated. In addition, LIBS successfully predicted the Mg content distributed within a pellet. This study demonstrated that LIBS is suitable as a rapid reagent-free method for the quantification of Mg in powdered infant formula and can provide spatial information with acceptable accuracy.     

Effect of lime on the dissolution of two phosphate rocks in acid soils

The effect of pH and calcium (Ca) on the dissolution of Gafsa (GPR) and Christmas Island A (CIPR) phosphate rocks (PR) was examined in closedincubation and open-leaching systems in six acid, Malaysian soils. The pH of the soils was increased to between 4.5 and 6.1 by incubating with calcium carbonate (CaCO₃); soil was also incubated with calcium chloride (CaCl₂) to provide equivalent amounts of Ca without causing any marked change in pH. In the closed-incubation system, dissolution of reactive GPR was overall higher (11–70%) than for the less reactive CIPR (12–43%) after 60 days of incubation. Dissolution of PR decreased with increasing levels of CaCO₃ or CaCl₂, but the decrease was more pronounced in CaCO₃-treated than in CaCl₂-treated soils. Increasing additions of CaCl₂ decreased the size of the available sink for Ca from 84.0 to 0 mmol (+) kg^–1 soil. Although the addition of CaCO₃ increased the cation-exchange capacity (CEC) of these variable-charge soils (from 23.0 to 199.0 mmol (+) kg^–1 soil), most of the newly-created exchange sites were occupied by Ca added through CaCO₃. This was responsible for the decrease in size of the sink for Ca. Addition of CaCO₃ also decreased the proton supply from 260.7 to 0 mmol (+) kg^–1 soil, which in conjunction with the decrease in size of the Ca sink decreased the dissolution of PR. The effect of CaCO₃ and CaCl₂ on PR dissolution varied between soils and was related to pH-buffering and the Ca-sink size. In an open-leaching system, large amounts of Ca (8–40%) added as CaCO₃ were removed in the leachate and hence the decrease in GPR dissolution with CaCO₃ addition was less in the open-leaching than in the closed-incubation system.     

Effect of cutting time, temperature, and calcium on curd moisture, whey fat losses, and curd yield by response surface methodology

Response surface methodology was used to study the effect of temperature, cutting time, and calcium chloride addition level on curd moisture content, whey fat losses, and curd yield. Coagulation and syneresis were continuously monitored using 2 optical sensors detecting light backscatter. The effect of the factors on the sensors’ response was also examined. Retention of fat during cheese making was found to be a function of cutting time and temperature, whereas curd yield was found to be a function of those 2 factors and the level of calcium chloride addition. The main effect of temperature on curd moisture was to increase the rate at which whey was expelled. Temperature and calcium chloride addition level were also found to affect the light backscatter profile during coagulation whereas the light backscatter profile during syneresis was a function of temperature and cutting time. The results of this study suggest that there is an optimum firmness at which the gel should be cut to achieve maximum retention of fat and an optimum curd moisture content to maximize product yield and quality. It was determined that to maximize curd yield and quality, it is necessary to maximize firmness while avoiding rapid coarsening of the gel network and microsyneresis. These results could contribute to the optimization of the cheese-making process.