V.H. Holsinger

Incorporation of whey products in extruded corn, potato or rice snacks

Abstract Sweet whey solids (SWS) or whey protein concentrate (WPC) were added at concentrations of 250 and 500 g/kg to corn meal, rice or potato flour to make snack products. Extrusion processing conditions included low shear, high shear, and the combination of high shear/low moisture. Increased specific mechanical energy (SME) was desired for expanding products, but SME was reduced as a result of incorporating WPC and SWS. Quality indices for expansion and breaking strength decreased significantly (P

Effects of Skim Milk Homogenization on Proteolysis and Rheology of Mozzarella Cheese

Abstract The influence of milk homogenization on proteolysis and functional properties of Mozzarella cheese was examined in an effort to develop low-fat Mozzarella with desirable textural and melting properties. Two-stage homogenization of skim milk at 6870/3430 kPa prior to the addition of nonhomogenized cream did not inhibit the meltability of full-fat or low-fat cheeses, when compared with cheeses made from nonhomogenized milk, but the meltability of full-fat cheese made from homogenized milk was greatly decreased. Homogenization of whole or skim milk had no significant effect on other rheological parameters or on proteolysis of αs1-casein in full-fat and low-fat cheeses. Refrigerated storage at 4 °C caused meltability and proteolysis to increase and the other parameters to decrease. Differences in fat content caused significant changes in hardness, springiness and meltability. Fat globule size and homogenization of protein affected proteolysis and rheology much less than fat content and storage time.

Reorganization of casein submicelles in Mozzarella cheese during storage

Abstract To gain a better understanding of the factors involved in textural changes in Mozzarella cheese during storage, electron microscopic imaging was used to compare the ultrastructure of the protein matrix on the day of stretching (0 weeks) and after 6 weeks of storage at 4 °C. Low-fat and full-fat cheeses were prepared from nonhomogenized milk and from milk homogenized at 10.3 and 17.2 MPa. Analysis of the stained electron density distribution in image transforms of the protein matrix revealed that spacing patterns of regular structures with the dimensions of casein submicelles changed during storage, in most cases forming larger aggregates at longer average spacings, but there were no significant changes in total electron density between fresh and stored cheeses. These effects were related to proteolysis. Submicelles in low-fat cheeses homogenized at 17.2 MPa reorganized differently, a likely result of decreased proteolysis. Submicelles formed part of a new membrane around fat globules in cheeses made from homogenized milk, as previously observed. Changes in submicelle size and distribution could explain some of the differences in texture properties between fresh and stored Mozzarella cheeses, and between products made from homogenized and nonhomogenized milk.

Electron-Density Patterns in Low-Fat Mozzarella Cheeses During Refrigerated Storage

Consumer demand for palatable low-fat foods has prompted the development and production of a wide variety of new foods. Consumer interest in low-fat dairy products has increased dramatically, and among the many new and improved dairy foods are some Mozzarella cheeses that have suitable textural properties yet contain less fat than part-skim varieties (Tunick et al., 1991). We further improved the textural properties of low-fat Mozzarella cheeses by adjusting the proportions of ingredients and processing conditions (Tunick et al., 1993). High levels of moisture in the non-fat substance significantly decreased the hardness, complex viscosity and elastic modulus, and the meltability increased during storage. These improvements in textural properties appeared to be most directly related to increased proteolysis under conditions of high moisture.

Effect of Carbon Dioxide under High Pressure on the Survival of Cheese Starter Cultures

A new processing method that rapidly forms curds and whey from milk has the potential to improve cheesemaking procedures if cheese starter cultures can tolerate the processing conditions. The survival of Lactobacillus delbrueckii ssp. bulgaricus, Lactococcus lactis ssp. lactis, or Streptococcus thermophilus through this new process was evaluated. Inoculated milk containing 0, 1, or 3.25% fat or Lactobacillus MRS broth or tryptone yeast lactose broth (depending on microorganism used) was sparged with CO2 to a pressure of 5.52 MPa and held for 5 min at 38 degrees C. Broth contained 7.93 to 8.78 log CFU/ ml before processing and 7.84 to 8.66 log CFU/ml afterward. Before processing, milk inoculated with L bulgaricus, L. lactis, or S. thermophilus contained 6.81, 7.35, or 6.75 log CFU/ml, respectively. After processing, the curds contained 5.68, 7.32, or 6.50 log CFU/g, and the whey had 5.05, 6.43, or 6.14 log CFU/ml, respectively. After processing, the pHs of control samples were lower by 0.41 units in broth, 0.53 units in whey, and 0.89 units in curd. The pH of the processed inoculated samples decreased by 0.3 to 0.53 units in broth, 0.32 to 0.37 units in whey, and 0.93 to 0.98 units in the curd. Storing curds containing L. lactis at 30 degrees C or control curds and curds with L. bulgaricus or S. thermophilus at 37 degrees C for an additional 48 h resulted in pHs of 5.22, 5.41, 4.53, or 4.99, respectively. This study showed that milk inoculated with cheese starter cultures and treated with CO2 under high pressure to precipitate casein-produced curds that contained sufficient numbers of viable starter culture to produce lactic acid, thereby decreasing the pH.

Overview: Cheese Chemistry and Rheology

Cheese is the generic name of a group of cultured fermented products represented world-wide in well over 500 varieties. More than 700 varieties are described in USDA Handbook No. 54 (Walter and Hargrove, 1969). Cheese represents perhaps one of the oldest means of food preservation and is made wherever animals are milked, whether the animal is a cow, buffalo, reindeer, goat, sheep, horse, camel, ass, yak or llama. Cheese is highly nutritious because it contains almost all of the protein, usually most of the fat, essential vitamins and minerals and other nutrients of milk in a concentrated form.

Inhibition of Proteolysis in Mozzarella Cheese Prepared from Homogenized Milk

Homogenization of milk was introduced almost 100 years ago to prevent the natural separation of milk phases, thus providing milk with more consumer appeal as a beverage and greater reliability and efficiency as a food ingredient (Trout, 1950). Many investigations of the physico-chemical changes that occur in milk during homogenization have been reviewed (Peters, 1964; Walstra, 1983), and there is now general agreement that the major effects are disruption of the fat globule membrane surrounding each droplet of milk fat (van Boekel and Walstra, 1989), an increase in the number of fat droplets and reduction in their size (Walstra, 1983), and formation of casein submicelles (Schmidt and Buchheim, 1970; Henstra and Schmidt, 1970). Each smaller fat droplet acquires a new “membrane” consisting of original fat globule membrane fragments complexed with casein submicelles (McPherson et al., 1984; Walstra and Oortwijn, 1982).

Detection of recombined butter by DSC

DSC can be used to quickly determine if a product labeled as butter is actually a recombined butter made without milk. Recombined butter is manufactured from anhydrous milk fat, skim milk powder, water, salt, and lecithin. Melting profiles of tempered samples of natural butter and recombined butter were alike, but DSC curves from 5 to 25°C of untempered refrigerated samples revealed that the enthalpy of the melting transition around 17–20°C was much higher for natural butter than for recombined butter. The procedure for differentiating the two products can be completed in less than 20 min.

Transmission Electron Microscopic Imaging of Casein Submicelle Distribution in Mozzarella Cheese

The increased demand for reduced-fat dairy products has spurred research into low fat (LF) cheeses, including Mozzarella. The LF Mozzarella procedure developed in our laboratory has been scaled up and tested in schools1 and is now being served on pizzas in the National School Lunch Program2. We have conducted studies with different cooking temperatures and homogenization pressures to determine the effects on casein breakdown, rheological properties, and microstructure in LF Mozzarella3,4, and are using these results to improve the quality of this cheese.

Nutritional aspects of reduced-fat cheese.

In response to consumer demand, the dairy industry has been developing new reduced and nonfat products to help meet dietary goals of reducing fat and calories. Because of its high fat content, cheese is a prime target for fat reduction, and offers great opportunities to market new varieties perceived as “healthy”, provided the reduced fat cheese is organoleptically acceptable.