The Iodine Concentration of Market Milk in Tennessee, 1981-1986.

Three hundred samples of processed milk from 10 milk processors in Tennessee were collected during the years 1981-1986, and analyzed for iodine concentration. Although some fluctuations occurred during the period, a downward trend was noted from the 287 µg/kg milk in 1981 to the 214 µg/kg milk in 1986. The overall average was 240 µg/kg. Seasonal differences were observed; spring samples had an average of 298 µg/kg; summer samples 200 µg/kg, and fall samples 234 µg/kg. Differences between plants were also found, with averages ranging from 153 to 344 µg/kg milk. Thirty-eight samples of raw tanker milk collected at one plant location during 1982-1986 had iodine concentrations ranging from 82 µg/kg to 1898 µg/kg, for an average of 240 µg/kg.

Determination of Calcium in Cottage Cheese by Titration.

The calcium concentration of cottage cheese has been determined by the use of disodium ethylene diaminetetraacetate as a calcium binder and calcein as an indicator. This method of analysis compares favorably with the atomic absorption procedure.

The Calcium Content of Cottage Cheese Made by Culture and Direct Acidification.

Using atomic emission spectrophotometry, the average calcium content of 29 market samples of cottage cheese made by the culture method was found to be 76.6 mg/100 g, and that of 18 market samples made by the direct acidification procedure was 91.2 mg/100 g. The average calcium content of 24 samples of lowfat cottage cheese was 87.5 mg/100 g and that of 23 samples of 4% cheese was 76.7 mg/100 g. Lowfat direct set cottage cheese had the most calcium, 102.3 mg/100 g. Curd made in the laboratory by the culture and direct acidification procedure showed no significant difference in calcium content.

Use of Sodium Substitutes in Cottage Cheese and Buttermilk.

Twenty-four market samples of cottage cheese had an average sodium concentration of 4.91 ± 1.20 mg/g. Two samples of cottage cheese formulated to contain 1.1% "Lite" and Zyest, and having sodium concentrations of 3.23 and 2.54 mg/g had significantly lower flavor scores than a sample containing 1.4% NaCl and having 6.25 mg of Na/g. The Standard Plate Counts and the yeast and mold counts on the cottage cheese after storing 10 d at 4°C were not different between samples containing salt, salt substitute or salt substitute plus a dry yeast preparation. Psychrotrophic bacteria were more numerous in the samples containing the yeast preparation. Four samples of buttermilk containing .015% "Zyest 45-F" and .25% NaCl, .25% "Lite" and .015% "Zyest 45-F", .25% NaCl, or .25% "Lite" had comparable flavor scores. The sodium concentrations of the four samples were 1.096, .793, 1.125 and .771 mg/g, respectively. The growth of yeasts and molds in samples containing "Zyest 45-F" and "Lite" was slightly but not significantly greater than the other three samples. Psychrotrophic counts on buttermilk after 7 d of storage at 4°C were much lower than the original counts, but were not influenced by the additives used.

Determination of Ethanol in Whey-Sugar Solutions by Freezing.

The composition of solutions undergoing yeast fermentation was simulated by using direct-acid-set cottage cheese whey containing increasing amounts of ethanol (0 to 5.4%) with decreasing amounts of sucrose (10 to 0%). Each decrease of 1 g of sucrose per 100 ml of whey accompanied by an increase of 0.54 g of ethanol decreased specific gravity 0.0046 unit and lowered the freezing point 0.159 H. Whey containing 10% added sucrose was treated as follows: (a) inoculated with Kluyveromyces fragilis , (b) carbohydrate splitting enzymes added and inoculated with K. fragilis and (c) carbohydrate splitting enzymes added and inoculated with Saccharomyces cerevisiae . All mixtures were incubated 48 h at 32 C during which six samples from each treatment were analyzed for total solids, specific gravity and freezing point. No difference (P>.05) was noted between samples treated with enzymes or those treated with the two yeasts cultures as related to decrease in total solids concentration or specific gravity. Each 0.001-H decrease in freezing point was accompanied by a total solids decrease of0.006 g per 100 g of whey in the non-enzyme treated sample, and 0.008 g and 0.010 g per 100 g whey in the enzyme-treated samples inoculated with K. fragilis and S. cerevisiae , respectively. Each 0.001-H change in freezing point was equivalent to a change of 0.00003 specific gravity unit in the non-enzyme treated sample and 0.000043 and 0.000048 specific gravity unit in the enzyme-treated samples inoculated with K. fragilis and S. cerevisiae , respectively. The precision with which freezing point can be determined suggests its use in evaluating the amount of ethanol produced during fermentation.

Fermentation of Lactose in Direct-Acid-Set Cottage Cheese Whey.

Kluyveromyces fragilis was more suitable than Candida pseudotropicalis or Kluyveromyces lactis for production of ethanol from whey. Direct-acid-set cottage cheese whey and the supernatant fluid resulting from heat treatment of the whey at 95 C for 20 min showed similar rates of fermentation when inoculated with K. fragilis . Inoculation rates of 10, 12 and 14 ml of active K. fragilis culture per 100 ml of media were not significantly different in rate of ethanol production. Samples incubated with K. fragilis at 35, 37, 40 and 42 C showed more rapid reduction in specific gravity than samples incubated at room temperature or 30 C. Lactose conversion in whey was 83% complete and in whey supernatant fluid, 77%.

Whey Protein Use in Cottage Cheese Dressing.

Cottage cheese whey protein concentrate prepared by heat precipitation and centrifugation was mixed with skimmilk, NaCl and xanthan gum and used as a dressing for cottage cheese curd. The resultant experimental cottage cheese contained more protein than a sample of commercial cottage cheese. The dressed curd particles of the experimental cheese tended to cling together and the flavor was somewhat flat. When evaluated by an 18-member sensory panel, it was given preference scores slightly below the commercial sample.

Use of Direct-Acid-Set Cottage Cheese Whey to Manufacture Sherbet.

Orange sherbet of 1% fat and 45 or 46% direct-add-set cottage cheese whey were compared to a control sherbet containing no whey. The titratable acidity was higher in sherbets containing whey. An untrained taste panel found no difference between the three sherbets studied, describing them as "like moderately."

Influence of storage, heat, and homogenization upon xanthine oxidase activity of milk.

Xanthine oxidase activity in milk was determined by measuring the rate of formation of vanillic acid from vanillin. Raw milk received at a dairy plant had .208 units xanthine oxidase activity per ml and after 24-h storage at 4 C, .228 units per ml. Upon further storage activity decreased. Heating the fresh raw milk in a water bath to 55 C increased xanthine oxidase activity to .236 units per ml. Partial inactivation of the enzyme occurred when milk was heated at 60, 65, or 70 C for 5 min, and destruction was almost complete with heat at 75 C for 5 min. Raw milk heated at 48 C for 5 min and homogenized at pressures between 70.3 and 281.2 kg/cm2 had xanthine oxidase activities which were a linear function of pressure and showed that each additional kg/cm2 pressure resulted in additional xanthine oxidase activity of .16 milliunits per ml of milk.

Tomato-Flavored Beverage and Onion-Flavored Chip Dip Made from Cottage Cheese Whey.

Whey from cottage cheese made by the short-set culture method was used to make tomato-flavored drink by addition of 6% dried tomato-spice flavoring material, and was found by 10 panelists to have a pleasing taste. Heat treatment of cottage cheese whey at 93 to 99 C resulted in a precipitate containing over 9% total solids. This precipitate was further concentrated by centrifugation or filtration through a cotton cloth. The precipitates were blended with xanthan gum and onion-flavoring to produce a chip dip.

Binding added iron to various milk proteins.

Binding of an added radionuclide to milk protein and casein components of cow's milk fractionated by the combination of Sephadex G-150 gel filtration and diethylaminoethyl-cellulose chromatography was determined. Iron-59 labeled ferric chloride was added directly to raw whole milk at a concentration of .02 and 10 ppm isotope and carrier, respectively, and held overnight at 4 C. Five milliliters of the skin milk were chromatographed on a Sephadex G-150 column and fractionated into casein, whey protein, and nonprotein materials. The casein fraction was chromatographed on a diethylaminoethyl-cellulose column and separated into its components, alphas-, beta-, and kappa-caseins. Casein bound about 85% of the added iron in skim milk; of this amount, 72, 21, and 4% were associated with the alphas-, beta, and kappa-caseins.