Comparison of Four Procedures of Cheese Meltability Evaluation

Two traditional cheese meltability tests, the Schreiber and Arnott, as well as two microwave modifications thereof were compared on a variety of mild and sharp cheddar, process American, and mozzarella cheeses and various process cheese products. There was a marked lack of correlation between the Schreiber and Arnott results indicating that at least two material properties control meltability. The effects of variations in heating time and oven temperature in the nonmicrowave tests and heating time in the microwave tests were determined. Differential scanning calorimetry did not reveal differences useful in predicting melting behavior.     

Arnott Test Correlates with Dynamic Rheological Properties for Determining Cheddar Cheese Meltability

Cheddar cheese with six different fat levels (34.3, 31.5, 26.8, 20.5, 12.6 and <1%) were manufactured and allowed to ripen 4 mo at 7°C. Melting characteristics of the cheeses were studied by the Arnott test and dynamic rheological testing. Meltability of Cheddar cheese was significantly influenced by its fat content as determined by the Arnott test. A significant correlation (r =–0.80) occurred between the minimum complex modulus G′ and meltability of Cheddar cheese. Minimum complex modulus G′ may be a useful predictor of cheese meltability.     

Prediction of processed cheese instrumental texture and meltability by mid-infrared spectroscopy coupled with chemometric tools

The objective of this study was to determine the potential of mid-infrared spectroscopy coupled with multidimensional statistical analysis for the prediction of processed cheese instrumental texture and meltability attributes. Processed cheeses (n = 32) of varying composition were manufactured in a pilot plant. Following two and four weeks storage at 4 °C samples were analysed using texture profile analysis, two meltability tests (computer vision, Olson and Price) and mid-infrared spectroscopy (4000–640 cm⁻¹). Partial least squares regression was used to develop predictive models for all measured attributes. Five attributes were successfully modelled with varying degrees of accuracy. The computer vision meltability model allowed for discrimination between high and low melt values (R² = 0.64). The hardness and springiness models gave approximate quantitative results (R² = 0.77) and the cohesiveness (R² = 0.81) and Olson and Price meltability (R² = 0.88) models gave good prediction results.     

Correlation Between Process Cheese Meltability Determined by Sensory Analysis,Computer Vision Method and Olson and Price Test

The meltabilities of 14 process cheese samples were determined at 2 and 4 weeks after manufacture using sensory analysis, a computer vision method, and the Olson and Price test. Sensory analysis meltability correlated with both computer vision meltability (R² = 0.71, P < 0.001) and Olson and Price meltability (R² = 0.69, P < 0.001). There was a marked lack of correlation between the computer vision method and the Olson and Price test. This study showed that the Olson and Price test gave greater repeatability than the computer vision method. Results showed process cheese meltability decreased with increasing inorganic salt content and with lower moisture/fat ratios. There was very little evidence in this study to show that process cheese meltability changed between 2 and 4 weeks after manufacture.     

Potassium Sorbate Diffusivity in American Processed and Mozzarella Cheeses

The diffusivity of potassium sorbate in cheeses was determined by using diffusion models and computer programming for examining the residual surface concentration and the penetration of surface-applied potassium sorbate into cheese. To determine diffusivity, the concentration of potassium sorbate in sliced cheese was measured by penetration time and distance from surface. The diffusivity was calculated by nonlinear regression with experimental data based on Fick's law. The diffusivity of potassium sorbate through American processed cheese was 1.31∞10^-6 cm²/sec and for Mozzarella cheese 6.74∞10^-7 cm²/sec. This indicated that Mozzarella cheese would maintain surface concentration of potassium sorbate above the critical fungistatic level two times longer than American processed cheese.     

Nondestructive Prediction of Moisture and Sodium Chloride in Cold Smoked Atlantic Salmon (Salmo salar)

ABSTRACT: Salt and moisture contents in cold-smoked salmon were determined using short-wavelength near-infrared (SW-NIR) reflectance spectroscopy (600 to 1100 nm). Partial least square (PLS) regression models yielded the best results among 3 linear regression methods tested. Back-propagation neural networks (BPNN) exhibited a somewhat better capability to model salt and moisture concentrations (Salt: R²= 0.824, RMS = 0.55; Moisture: R²= 0.946, RMS = 2.44) than PLS (Salt: R²= 0.775, RMS = 0.63; Moisture: R²= 0.936, RMS = 2.65). Selection of samples from different axial locations on a fish did not affect the prediction error for salt or WPS but affected the prediction error for moisture.     

Effects of fat on the properties of halloumi cheese

Halloumi cheese was produced from 11 bovine milks with fat contents of 1.61–4.04%, giving a range of 32–53% fat in dry matter (FDM) in the cheeses. Starter culture and/or microparticulated whey protein (Simplesse ^® 100(E)) was also added to selected batches of milk. Hardness decreased with increasing FDM, with increase in moisture and with lower pH. On sensory evaluation, there was an increase in preference score with FDM ( R ²   = 0.8). Inclusion of microparticulated whey protein may have had a fat mimetic effect, as preference scores otherwise decreased with increasing protein levels ( R ² = 0.75).     

Elimination of Listeria monocytogenes in soft and red smear cheeses by irradiation with low energy electrons

Soft and red smear cheeses are frequently contaminated by Listeria monocytogenes , sometimes at relatively high concentration (< 10⁵ CFUg^-1). This bacterium is radiosensitive (D₁₀ value of approximately 0.45 kGy) but irradiation of the whole cheese by X-rays induced off-flavours when the dose exceeded 1.0 kGy. Irradiation could be effective in eliminating L. monocytogenes only from lightly contaminated cheeses (> 10²CFU g^-1).
L. monocytogenes appears only in the rind (where the pH is greater than 6.3) and never grows in the core of the cheese. Under these conditions, a specific irradiation of the rind after ripening, with a low-energy electron beam at relatively high doses (up to 3.0 kGy), allows the total elimination of L. monocytogenes in heavily contaminated samples (10⁵-10⁶ CFU g^-1) without noticeable modifications of the organoleptic properties of the cheese.     

Prediction of Rice Starch Quality Parameters by Near-Infrared Reflectance Spectroscopy

ABSTRACT: A rapid predictive method based on near-infrared spectroscopy (NIR), was developed to measure rice starch quality parameters. A calibration set of 100 samples and validation set of 62 samples of rice flour of Chinese genotypes was used. Results of partial least squares modeling indicated that NIR was reasonably accurate in predicting apparent amylose content (AAC) (standard error of prediction [SEP] = 1.39 percentage units, coefficient of determination [R²] = 0.91); pasting parameters of setback (SB) (SEP = 13.6 RVU, R²= 0.92), and breakdown (BD) (SEP = 10.2 RVU, R²= 0.88); and gelatinization peak temperature (T_p) (SEP = 1.33 °C, R²= 0.89). Gel consistency (GC), cool paste viscosity (CPV), gelatinization onset temperature (T_o), and textural properties of chewiness, hardness and gumminess, were modeled less well with R2 between 0.75 and 0.86. NIR analysis is sufficiently accurate for routine screening of large numbers of samples in early generation selection in rice breeding programs.     

MOLD GROWTH AND PRESENCE OF AFLATOXIN IN SOME TURKISH CHEESES

Twenty-five random fresh market samples of Van herby cheese and pickled white cheese were examined for molds and aflatoxins. The mean total mold count in Van herby cheese was 2.50 × 10⁵/g; in pickled white cheese it was 4.95 × 10⁴/g. The mycoflora on the cheeses were determined. In all cheeses, over 65% of molds were Penicillium species . Aspergillus made up 0 to 1.6 % and 2.6 % to 4.0 % of the mold on pickled white cheese and Van herby cheese, respectively. Other isolated molds belonged to Mucor, Geotrichum and Trichoderma genera. None of the samples contained aflatoxins and none of the 6 Aspergillus isolates was an aflatoxin producer .     

Short communication: comparison of covered and uncovered Schreiber test for cheese meltability evaluation

Schreiber meltability tests were performed on glass Petri dishes, with and without the Petri dish cover placed over the cheese samples, at 100, 150, and 232 degrees C. Meltability of different process cheese and Cheddar cheese samples was determined based on the melt spread distance and area. At the test temperature of 232 degrees C, the covered Schreiber was significantly superior to the uncovered test because of no crust formation, no browning, and a circular melting pattern, which were attributed to the barrier effect of covering the cheese samples (which inhibits moisture loss during the test). The covered Schreiber test data were statistically more robust as measured by the lower average coefficient of variation than the data from the traditional uncovered Schreiber test.     

Chemometric Formulas Based on Physical Properties of Single-cooked Milled Rice Grains for Determination of Amylose and Protein Contents

ABSTRACT: Chemometric formulas for predicting amylose content (AC) and protein content (PC) were developed based on the surface and overall physical properties of single-cooked milled rice grains as predictive variables. The formula with 8 predictors for AC determination exhibited the highest accuracy (coefficient of determination: R²= 0.952, standard error of calibration: SEC = 1.77) for calibration and the lowest standard error of prediction (SEP = 2.07) for unknown samples (AC: 0 to 30%). The formula with 7 predictors was effective in enhancing the prediction accuracy (SEP = 1.32) among non-waxy samples in a narrow range of AC (15 to 20%). The formula with 8 predictors for PC determination showed a higher accuracy (R²= 0.449 and 0.470) for both calibration and prediction than that of a conventional 3-grain method (R²= 0.168 and 0.124). It was possible to accurately determine AC using physical measurement of single grains instead of chemical analysis.     

CHANGES IN EQUILIBRIUM MODULUS AND αsl-CASEIN BREAKDOWN DURING THE RIPENING OF PORT SALUT ARGENTINO CHEESE AS AFFECTED BY FROZEN STORAGE

The effect of the freezing, frozen storage and thawing on textural parameters and α_sl-casein breakdown during the ripening of Port Salut Argentino cheese was studied. Moisture content, salt concentration, casein profiles and asymptotic equilibrium modulus were monitored in control cheeses ripened at 5C and in cheeses, stored at -22C for 30 days, thawed and ripened at 5C, for different ripening times (1, 6, 13, 27 and 56 days) and two sampling zones (central and external). The freezing process significantly increased the rate of α_sl-casein and α_sl-I-casein hydrolysis. This process may affect the susceptibility of α_sl-casein to chymosin attack and also the availability of hydrolytic enzymes released by damaged microorganisms, which may contribute to the faster hydrolysis of α_sl-I-casein. The freezing process did not significantly affect the decay rates of asymptotic equilibrium modulus. First order kinetics constants for decay of the asymptotic equilibrium modulus were 3.71 10^-2day^-1 (control cheeses, central zone), 8.48 10^-2 day^-1 (control cheeses, external zone), 4.52 10^-2 day^-1 (frozen cheeses, central zone), and 11.43 10^-2 day^-1 (frozen cheeses, external zone). Significant differences in the decay rates of asymptotic equilibrium modulus were found between central and external zones in control and frozen cheeses primarily due to differences in moisture contents of the sampling zones.     

EFFECT OF ULTIMATE pH ON THE QUALITY CHARACTERISTICS OF PORK

A study was conducted to characterize the relationship between Longissimus thoracis ultimate pH(LTpH) and pork quality. Animals (n = 47) were selected based on LTpH measured at 24 h postmortem. Data were analyzed using regression procedures with ultimate pH as the independent variable, and relationships were determined to be linear (L), quadratic (Ql or cubic (C). Ultimate pH explained 79% (C) of the variation in subjective color, which increased as pH increased. Drip loss, purge loss and L* value decreased as LTpH increased (R²= 0.57C, 0.77 Q and 0.68 Q, respectively). Shear force decreased and sensory juiciness increased as LTpH increased (R²= 0.26Q and 0.46C, respectively). However, of flavor intensity increased as LTpH fell below pH 5.2 or exceeded 6.1(R²=0.52C). Increasing LTpH, up to a point, will improve fresh pork quality and processed meat properties, whereas, above approximately 6.1, of-flavor may increase.     

THE PSYCHOPHYSICS OF POURING, SPREADING AND IN-MOUTH VISCOSITY

The sensory viscosity of low calorie viscoelastic syrups in the mouth, while pouring out of a bottle, and spreading over a flat surface was satisfactorily estimated from the fundamental physical properties of these fluids. Appropriate sensory perception mechanisms were identified and linked to the operating conditions of each sensory test through psychophysical models. Oral sensory viscosity correlated with the shear stress in the mouth (R²= 0.96) (Kokini et al. 1977); pouring sensory viscosity correlated with the cross sectional area filled by the fluid at the neck of the bottle (R²= 0.86); and spreading sensory viscosity correlated inversely with the radial growth of the spreading fluid puddle (R²= 0.96).     

Study of organic acids, volatile fraction and caseins of a new Halloumi-type cheese during ripening in whey brine

Organic acids, fat hydrolysis, volatile compounds and sensory characteristics of a new brine cheese which combines characteristics of Halloumi and Feta cheeses during its ripening in whey brine (100g NaCl L⁻¹) were studied. Thermotolerant protease of Mucor miehei as a coagulant enzyme and a mixture of thermotolerant starter cultures Enterococcus faecium 0165 (0.5% w/w) and Lactobacillus casei 80 10D were used. Good quality new Halloumi-type cheese was produced with higher proteolysis than traditional Halloumi cheese kept in whey brine. The volatile compounds identified comprised alcohols, aldehydes, ketones, acids, esters, hydrocarbons and sulphur compounds. Ethanol was the dominant volatile compound determined. Lactic acid was the dominant acid produced; its concentration increased during ripening, reaching a maximum value of 9929 mg kg⁻¹ at day 30. Acetic acid was also found in high amounts, which increased during cheese ripening. Lipolysis of cheese was not intense. The most abundant acids of the mature cheese were palmitic, oleic and acetic acid. The Halloumi-type cheese scored higher in the sensory analysis when fresh than did the mature cheese.     

Effect of natural cheese characteristics on process cheese properties

Natural cheese is the major ingredient utilized to manufacture process cheese. The objective of the present study was to evaluate the effect of natural cheese characteristics on the chemical and functional properties of process cheese. Three replicates of 8 natural (Cheddar) cheeses with 2 levels of calcium and phosphorus, residual lactose, and salt-to-moisture ratio (S/M) were manufactured. After 2 mo of ripening, each of the 8 natural cheeses was converted to 8 process cheese foods that were balanced for their composition, including moisture, fat, salt, and total protein. In addition to the standard compositional analysis (moisture, fat, salt, and total protein), the chemical properties (pH, total Ca, total P, and intact casein) and the functional properties [texture profile analysis (TPA), modified Schreiber melt test, dynamic stress rheometry, and rapid visco analysis] of the process cheese foods were determined. Natural cheese Ca and P, as well as S/M, significantly increased total Ca and P, pH, and intact casein in the process cheese food. Natural cheese Ca and P and S/M also significantly affected the final functional properties of the process cheese food. With the increase in natural cheese Ca and P and S/M, there was a significant increase in the TPA-hardness and the viscous properties of process cheese food, whereas the meltability of the process cheese food significantly decreased. Consequently, natural cheese characteristics such as Ca and P and S/M have a significant influence on the chemical and the final functional properties of process cheese.     

Use of dry milk protein concentrate in pizza cheese manufactured by culture or direct acidification

Milk protein concentrate (MPC) contains high concentrations of casein and calcium and low concentrations of lactose. Enrichment of cheese milk with MPC should, therefore, enhance yields and improve quality. The objectives of this study were: 1) to compare pizza cheese made by culture acidification using standardized whole milk (WM) plus skim milk (SM) versus WM plus MPC; and 2) compare cheese made using WM + MPC by culture acidification to that made by direct acidification. The experimental design is as follows: vat 1 = WM + SM + culture (commercial thermophilic lactic acid bacteria), vat 2 = WM + MPC + culture, and vat 3 = WM + MPC + direct acid (2% citric acid). Each cheese milk was standardized to a protein-to-fat ratio of approximately 1.4. The experiment was repeated three times. Yield and composition of cheeses were determined by standard methods, whereas the proteolysis was assessed by urea polyacrylamide gel electrophoresis (PAGE) and water-soluble N contents. Meltability of the cheeses was determined during 1 mo of storage, in addition to pizza making. The addition of MPC improved the yields from 10.34 +/- 0.57% in vat 1 cheese to 14.50 +/- 0.84% and 16.65 +/- 2.23%, respectively, in vats 2 and 3 and cheeses. The percentage of fat and protein recoveries showed insignificant differences between the treatments, but TS recoveries were in the order, vat 2 > vat 3 > vat 1. Most of the compositional parameters were significantly affected by the different treatments. Vat 2 cheese had the highest calcium and lowest lactose contencentrations. Vat 3 cheese had the best meltability. Vat 1 cheese initially had better meltability than vat 2 cheese; however, the difference became insignificant after 28 d of storage at 4 degrees C. Vat 3 cheese had the softest texture and produced large-sized blisters when baked on pizza. The lowest and highest levels of proteolysis were found in vats 2 and 3 cheeses, respectively. The study demonstrates the use of MPC in pizza cheese manufacture with improved yield both by culture acidification as well as direct acidification.     

DETECTION OF STAPHYLOCOCCUS AUREUS PRODUCTS IN FOODS USING ENZYME LINKED IMMUNOSORBENT ASSAY AND SPECTROPHOTOMETRIC THERMONUCLEASE ASSAY

The comparative sensitivity of an enzyme linked immunosorbent assay (ELISA) using four different antistaphylococcal antisera and a spectrophotometric assay for thermonuclease were determined using cheese and ravioli samples seeded with strains of Staphylococcus aureus and S. epidermidis. The ELISA used antisera to enterotoxin A, enterotoxin B, S. aureus strains 14609 (human), and UNH-570 (bovine). The 570 ELISA and spectrophotometric thermonuclease assay were of comparable sensitivity and detected seeded culture in concentrations as low as 2 × 10⁷ CFU/g of cheese. A simple two hour method for extracting thermonuclease from foods was 50% efficient when as little as 50 ng of purified enzyme was seeded per g of cheese. Analyses of 43 commercial cheeses for viable S. aureus found five (12%) positive with 3 × 10⁴ CFU/g of cheese being the highest counts detected. All samples were negative by ELISA and thermonuclease assay. A simple screening procedure for demonstration of S. aureus contamination of foods is discussed.     

Correlating mozzarella cheese properties to production processes by rheological,mechanical and microstructure study: Meltability study and Activation energy

Meltability is one of the most important properties of mozzarella cheese as it is generally used melted, and neither too high nor too low meltability can be accepted by consumers. However, there is no widely accepted objective method to evaluate cheese meltability. The most commonly used method, the Schreiber test, cannot be used as a standard evaluation method because of its varying test conditions. Another method based on the temperature sweep of Small Amplitude Oscillatory Shear analysis (SAOS) is rarely used for meltability evaluation. The aim of this study is therefore to study the Schreiber test and to develop the method of SAOS to evaluate cheese meltability. Based on SAOS, an Arrhenius plot is obtained from a temperature sweep and the activation energy (Ea) is calculated from the Arrhenius plot within the temperature range of 30 °C to 45 °C. This study compares these two methods on eleven mozzarella cheese samples with different stretching conditions, pH, fat or calcium content. It is found that the meltability of mozzarella cheese produced with different stretching conditions has no significant difference; high fat and low fat samples have the highest and lowest meltability respectively; and samples with low draining pH have similar meltability with the ones with low calcium content, and vice versa.