Pasteurized Process Cheese Spreads Research Articles

Utilization of cheddar cheese containing nisin as an antimicrobial agent in other foods

Cheddar cheese made with nisin-producing lactococci contained between 400 and 1200 IU of nisin per gram of cheese. Cultures used were Lactococcus lactis ssp. cremoris JS102, a nisin-producing transconjugant developed in the laboratories of Dr. L.L. McKay and Lactococcus lactis ssp. lactis NCDO 1404 obtained from the National Collection of Food Bacteria, Reading, England. Pasteurized process cheese spreads with 53% and 60% moisture and 0, 301 and 387 IU nisin/g were manufactured and inoculated with 2000 spores of Clostridium sporogenes PA 3679 during manufacture. The heat process did not reduce nisin activity in the cheese spreads. The spreads were incubated at 22° and 37°C for 90 days. Spoilage was detected by the presence of gas and/or odor in the packages. The shelf-life of the nisin-containing cheese spreads was significantly greater than that of the control cheese spreads at the lower temperature at both moisture levels, whereas the keeping quality of the higher moisture cheeses at the higher temperature was not significantly different. Club cheese or cold pack cheese spreads with moisture levels of 44% and 60% and 0, 100 and 300 IU nisin/g were made. These cold processed cheese spreads were inoculated with 1000 cfu per g of Listeria monocytogenes V7, Staphylococcus aureus 196E and spores of C. sporogenes PA 3679. Heat shocked spores of PA 3769 at the same number were added to separate lots of the cheese spread. The cold pack cheese spreads were incubated at 23° and 37°C for up to 8 weeks. Samples were taken weekly and analyzed for surviving organisms. Significant reductions in numbers of the non-sporeforming test microbes were noted at both temperatures, at both moisture levels and both levels of nisin. Heat shocking the spores was needed to show reduction in numbers during the storage of the cold pack cheese spreads. The data obtained in this study suggest that the use of nisin-containing cheese as an ingredient in pasteurized process cheese or cold pack cheese spreads could be an effective method of controlling the growth of undesirable microorganisms in these processed foods.

Contribution of Composition, Physicochemical Characteristics and Polyphosphates to the Microbial Safety of Pasteurized Cheese Spreads

Pasteurized process cheese spread was manufactured with moisture contents of 52, 54, 56 and 60%. Three different types of phosphate emulsifier were used, disodium ortho-phosphate and two commercially-available polyphosphates, S9 and S9H. Pasteurized, processed cheese spreads were inoculated with approximately 1 × 104Clostridium botulinum spores/gram cheese in the cook kettle, held 3 min at 80°C, hot-filled into glass containers, and incubated at 30°C. Samples were analyzed over 30 weeks for growth of C. botulinum and toxigenesis. Toxin was first detected in 60% moisture cheese with disodium ortho-phosphate as the emulsifier at 8 weeks and in 60% moisture cheese with the test polyphosphates as the emulsifier when tested at 20 weeks. None of the other cheese formulations were toxic at 20 weeks. Toxin production correlated statistically to time, moisture, pH and phosphate type.

Shelf-Life of Pasteurized Process Cheese Spreads Made from Cheddar Cheese Manufactured with a Nisin-Producing Starter Culture

Cheddar cheese made with a nisin-producing starter culture and Cheddar cheese made with a commercially available starter culture were used to manufacture pasteurized process cheese spreads at low and high moisture percentages (53 and 60%, respectively). Composition did not differ between spreads of similar moisture content with and without nisin. The nisin contents of cheese spreads were 301 and 387 IU/g at the high and low moisture percentages, respectively. Nisin was not inactivated by the thermal process used during cheese spread manufacture. Shelf-life of pasteurized process cheese spreads was determined during storage at 22 and 37°C. Low moisture cheese spreads with nisin had a longer shelf-life than corresponding cheese spreads without nisin when cheeses were incubated at either temperature. High moisture cheese spreads with nisin had a longer shelf-life than control spreads when cheeses were incubated at 22°C. However, shelf-life did not differ between high moisture spread with nisin and cheese spreads without nisin when cheeses were incubated at 37°C.

Antibotulinal Effectiveness of Nisin in Pasteurized Process Cheese Spreads

Pasteurized process cheese spreads were prepared at moisture levels ranging from 52 to 57% with added sodium chloride at levels from 0 to 2.0%, with disodium phosphate levels ranging from 1.4 to 2.5%, and with nisin levels of 0 to 250 ppm. Clostridium botulinum spores were added at a level of approximately 1000 spores per gram of cheese spread except for control batches and one experiment where the spore levels were varied (10–1000 spores/g). The cheese spreads were incubated at 30°C for up to 48 weeks. Nisin is an effective antibotulinal agent in pasteurized process cheese spreads. Addition of nisin allows formulation of pasteurized process cheese spreads with reduced sodium levels (addition of 1.4% disodium phosphate and no added sodium chloride) or slightly higher moisture levels (55–57%) by comparison to typical commercial pasteurized process cheese spreads. Higher levels of nisin (100 and 250 ppm) were required to prevent outgrowth of botulinal spores in cheese spreads with highest moisture levels or most greatly reduced sodium levels. However, in a cheese spread of 52% moisture prepared with 2.5% disodium phosphate but no added sodium chloride, a nisin level of 12.5 ppm was able to prevent completely outgrowth and toxin production by C. botulinum.

Evaluation of Factors Involved in Antibotulinal Properties of Pasteurized Process Cheese Spreads

Pasteurized process cheese spreads with various levels of sodium chloride, disodium phosphate, moisture and pH were challenged with spores of Clostridium botulinum types A and B. Response surface methodology was used to design experiments that would yield maximum results with the minimum number of trials. Supplemental experiments were added to further clarify the response and to examine combinations of special interest. A total of 304 treatment combinations (batches) was incubated at 30°C, and five samples from each batch were taken at predetermined intervals up to 42 wk of incubation and tested for botulinal toxin. Sodium chloride and disodium phosphate inhibited botulinal toxin production with similar effectiveness. The inhibitory effect of low pH (<5.7) and low moisture (<54%) levels on botulinal toxin production was as expected, i.e., as either pH or moisture went up, it was necessary to increase sodium chloride and/or phosphate concentrations to compensate. Differences in water activity between cheese spreads with different compositions were observed but they were too small to use for controlling the properties of the products, e.g., a range of 9% in moisture level (51 to 60%) produced only 0.022 variation in water activity. Combinations of the above factors were developed for safe pasteurized process cheese spreads containing up to 60% moisture.

Challenge of Pasteurized Process Cheese Spreads with Clostridium botulinum Using In-Process and Post-Process Inoculation

A study was done to evaluate the antibotulinal safety of pasteurized process cheese spreads and to compare two different published methods of inoculation of cheese spreads with Clostridium botulinum spores. Pasteurized process cheese spreads of various compositions were challenged with approximately 1,000 spores per g of C. botulinum types A and B. Two different methods of challenge were tested: (a) an “in-process” or “hot” inoculation in which a spore suspension was added to hot cheese spread in a cooker during agitation, and (b) a “post-process” or “cold” inoculation in which 0.1 ml of heat-shocked (80°C, 10 min) spore suspension was added to cheese spread already packed in glass jars and stirred. Certain products that were thought to have an adequate margin of safety by hot challenge studies became toxic when challenged by the cold method. Experiments to check localization of the spores in cold-inoculated cheese spread produced results suggesting that the concentration of the inoculum plus the localized diluting effect of added water in the cold-inoculated cheese spread probably account for the discrepancy between the two procedures.

Toxin Production by Clostridium botulinum in Shelf-Stable Pasteurized Process Cheese Spreads

Five non-refrigerated, pasteurized process cheese spreads, considered shelf-stable, were studied for their ability to support growth and toxin production by spores of Clostridium botulinum types A and B. Based on pH and water activity (aw) Cheese with Bacon, Limburger, Cheese Whiz, Old English, and Roka Blue cheese spreads were selected for the study. The pH ranged from 5.05 to 6.32 and the aw from 0.930 to 0.953. Fifty jars of each cheese spread were inoculated with 24,000 spores each; an additional 50 jars of the Cheese with Bacon spread received 460 spores each. The inoculum consisted of five type A and five type B strains in 0.1 ml of 0.85% NaCl. At 35 C, 46 jars of Limburger and 48 jars of Cheese with Bacon spread, which received the greater inoculum, became toxic starting at 83 and 50 days, respectively. One jar of Cheese with Bacon spread which received 460 spores became toxic. The average toxicity of the Limburger was 3000 MLD/ml of extract as compared with 54 MLD/ml for the Cheese with Bacon spread. Results of this study will be considered in determining whether these cheese spread products should be treated as low-acid canned foods under the Good Manufacturing Practice Regulations of the Food and Drug Administration.

A Challenge of Pasteurized Process Cheese Spread with Clostridium botulinum spores

Pasteurized process cheese spread with pimientos, packaged in glass jars, inoculated during processing with 1000 spores of Clostridium botulinum per gram, developed neither gas nor toxin at 52 or 54% moisture when sodium phosphate was used as the emulsifier. When sodium citrate was the emulsifier, the product developed gas at 52% moisture and became toxic at 54%. At 58% moisture the product became gassy and toxic with either emulsifier. Since the product is commercially manufactured at 52% moisture with phosphate emulsifier, a substantial margin of safety exists.

SPECIFICITY OF THE FERRIC‐H2SO4 REAGENT FOR ALGINATES

SUMMARY— Alginate in foods was isolated from papain digests of the samples as the insoluble calcium salt. dispersed by sodium hexametaphosphate and a 1‐ to 5‐ml aliquot of the dispersion 50–250 μg of sodium alginate) dried at 100°C. Heating of the anhydrous sample in the presence of the ferric‐H2SO4 reagent for 12 min at 60°C produced a pink color with maximum absorption at 490–515 mμ and maximum density after aging for 90 min at 29±1°C. Under these conditions, proteins, amino acids (except tryptophane), other carbohydrates, vitamins. food additives and incipients did not interfere. The presence of water in the medium rendered the reaction nonspecific and increasing the temperature above 60°C or heating for longer periods at lower temperatures resulted in color formation by other polyuronides, especially pectin and pectic acid. Recoveries of alginate from several products were good: Milk, 94–98%; ice cream, 93.5–98%; pasteurized process cheese spread. 92.6‐95%; chocolate milk, 92.4‐95%; dietetic foods, 90‐97.2%.

Effects of Proteolysis of Natural Cheese on Body and Melting Properties of Pasteurized Process Cheese Spread

Summary Cheddar and Dariworld cheese were specially made and ripened for six months. At regular intervals they were analyzed and made into pasteurized process cheese spreads. The original making processes were varied to give both normal and abnormally sweet (high pH) lots of both varieties. Proteolytic changes, measured by nitrogen and formol nitrogen as per cent of total nitrogen soluble in a sodium citrate-HCl extract of cheese at pH 4.4 ± 0.05, were quite similar in all modifications excepting sweet Dariworld; proteolysis in sweet Dariworld exceeded that of all other treatments. In spite of this general similarity, satisfactory penetrometer and melting values occurred only in spreads made from normal cheese and then only when soluble nitrogen had developed to approximately 12 to 15% of total nitrogen and formol nitrogen to 2 to 3% of total nitrogen. Changes in pH during making and curing were more significant than proteolysis in determining rheological properties of the cheese spreads.

Composition and Bacterial Growth as Factors Affecting the Body of Pasteurized Process Cheese Spread

Summary Effects of variations of composition on the firmness of pasteurized process cheese spreads made with Dariworld cheese were determined by (1) modifying moisture and fat contents of a base formula and (2) by substituting nonfat dry milk (NDM), lactose, or dried whey for part of the solids-not-fat supplied by cheese (CSNF). Firmness of spreads varied inversely with moisture, where the proportion of solids-not-fat to fat was held constant. Firmness was not affected by changes in fat when the ratio of moisture to solids-not-fat was not altered. Use of increased amounts of lactose and dried whey decreased the firmness of spreads. Addition of NDM was less effective in decreasing firmness. Firmness increased when the proportion of moisture to cheese solids-not-fat (H 2 O/CSNF) was decreased; this relationship was notably regular for all modifications. Some samples containing added lactose and NDM increased markedly in firmness and acidity during 90 days of storage at 90 F.; gram-positive bacilli were found in large numbers in all batches of such firm-bodied spreads. Spreads without added NDM or lactose did not increase in firmness during storage for 90 days at 90 F., regardless of levels of moisture or fat.

Acidity and Age of Natural Cheese as Factors Affecting the Body of Pasteurized Process Cheese Spread

Summary Two varieties of cheese, Cheddar and Dariworld, were made with normal and high pH. They were aged at 50° F. and at various intervals were used individually as the base for cheese spreads of constant composition. The acceptability of the spreads was measured organoleptically, by penetrometer, and by melting tests. It was found that natural cheese with high pH was undesirably firm in body at every age; this firmness persisted in the spreads made from such cheese. All tests showed that the age of the cheese when processed into spread affected acceptability. Improvements were found as the cheese aged to 60 days. After that, penetrometer values tended to show increased hardness and melting tests continued to increase with age. Storage of spreads at 50° F. was possible without significant changes in penetrometer values for at least 90 days, but deterioration was measurable after 15 days of storage at 90° F. and had reached a critical level for commercial use in approximately 30 days. The normal Dariworld cheese appeared to be superior to normal Cheddar cheese for making this type of spread. It reached desirable processing characteristics at an earlier age and the spread made from it was more durable in storage.

A Melting Test for Pasteurized Process Cheese Spreads

A Melting Test for Pasteurized Process Cheese Spreads