Modifications to established fiber methods may be required to quantify cellulose from flow aids in grated Parmesan cheese.

Reliable detection and quantification of flow-aid concentrations in grated cheese is warranted for both quality assurance and to prevent fraud, yet no official method exists. This study evaluated enzymatic-gravimetric methods that quantify insoluble dietary fiber, as well as near-infrared spectroscopy (NIR), for their suitability to measure cellulose and flow-aid concentrations in ground Parmesan with known amounts of commercial flow-aid preparations. The range of flow-aid concentrations spanned 0 to 5.01 g/100 g of cheese, corresponding to 0 to 1.39 g/100 g of cellulose. Use of the total dietary fiber assay, with or without modifications, consistently overestimated flow-aid concentrations by formation of aggregates that were presumably difficult to digest. Increasing protease amounts reduced but did not eliminate this issue. In contrast, the integrated dietary fiber assay and NIR spectroscopy were suitable methods for quantification of cellulose and flow aid. However, analyzing control cheeses without flow aid proved difficult with both methods. For these samples, the integrated dietary fiber assay and NIR spectroscopy calibrated for cellulose gave higher than actual values with poor precision (0.50 ± 0.36 and 0.38 ± 0.22 g/100 g, respectively). However, NIR calibrations for flow aid (which also contained starch), instead of cellulose, specifically yielded more accurate results for samples with 0 g/100 g of flow aid (0.06 ± 0.14 g/100 g). In general, prediction of higher concentrations of flow aid via NIR spectroscopy had lower accuracy than with the integrated dietary fiber assay; however, results obtained via NIR spectroscopy had lower variability. The total dietary fiber assay always overestimated cellulose in ground Parmesan, and further modifications are necessary to obtain accurate results. Differences between the pH at which protein digestion occurs (lower for the integrated dietary fiber assay than the total dietary fiber assay) may have contributed to differences in results.

Short communication: Development of a rapid laboratory method to polymerize lactose to nondigestible carbohydrates.

Nondigestible carbohydrates with a degree of polymerization between 3 and 10 (oligosaccharides) are commonly used as dietary fiber ingredients in the food industry, once they have been confirmed to have positive effects on human health by regulatory authorities. These carbohydrates are produced through chemical or enzymatic synthesis. Polylactose, a polymerization product of lactose and glucose, has been produced by reactive extrusion using a twin-screw extruder, with citric acid as the catalyst. Trials using powdered cheese whey permeate as the lactose source for this reaction were unsuccessful. The development of a laboratory method was necessary to investigate the effect of ingredients present in permeate powder that could be inhibiting polymerization. A Mars 6 Microwave Digestion System (CEM Corp., Matthews, NC) was used to heat and polymerize the sugars. The temperatures had to be lowered from extrusion conditions to produce a caramel-like product and not decompose the sugars. Small amounts of water had to be added to the reaction vessels to allow consistent heating of sugars between vessels. Elevated levels of water (22.86 and 28.57%, vol/wt) and calcium phosphate (0.928 and 1.856%, wt/wt) reduced the oligosaccharide yield in the laboratory method. Increasing the citric acid (catalyst) concentration increased the oligosaccharide yield for the pure sugar blend and when permeate powder was used. The utility of the laboratory method to predict oligosaccharide yields was confirmed during extrusion trials of permeate when this increased acid catalyst concentration resulted in similar oligosaccharide concentrations.

Technical note: The equivalency of sodium results in cheese digested by either dry ashing or microwave-accelerated digestion.

Analysis of dairy products for minerals such as sodium requires mineralization of the sample, which is typically done by either dry ashing or atmospheric wet ashing; both methods are time consuming and wet ashing requires the repeated handling of hot acid. A rapid method using microwave-accelerated acid digestion before atomic absorption spectrometry to measure sodium was compared with dry ashing in 138 samples of blue cheese (in duplicate) that varied in sodium content and age. Linear regression of the results obtained within different cheese salting treatments and sampling locations over time showed that the methods were equivalent in terms of linearity and the slope of the line. A consistent bias was observed, with lower sodium concentrations being quantified during atomic absorption spectrometry for the microwave-digested samples. Evaluation of this difference by the 2 one-sided test (TOST) procedure showed that the confidence intervals of the percentage difference between the methods fell within the predetermined acceptable percentage difference. We conclude that this rapid microwave digestion procedure of blue cheese yielded equivalent results to dry ashing.

The effect of sodium reduction with and without potassium chloride on the survival of Listeria monocytogenes in Cheddar cheese.

Sodium chloride (NaCl) in cheese contributes to flavor and texture directly and by its effect on microbial and enzymatic activity. The salt-to-moisture ratio (S/M) is used to gauge if conditions for producing good-quality cheese have been met. Reductions in salt that deviate from the ideal S/M range could result in changing culture acidification profiles during cheese making. Lactococcus lactis ssp. lactis or Lc. lactis ssp. cremoris are both used as cultures in Cheddar cheese manufacture, but Lc. lactis ssp. lactis has a higher salt and pH tolerance than Lc. lactis ssp. cremoris. Both salt and pH are used to control growth and survival of Listeria monocytogenes and salts such as KCl are commonly used to replace the effects of NaCl in food when NaCl is reduced. The objectives of this project were to determine the effects of sodium reduction, KCl use, and the subspecies of Lc. lactis used on L. monocytogenes survival in stirred-curd Cheddar cheese. Cheese was manufactured with either Lc. lactis ssp. lactis or Lc. lactis ssp. cremoris. At the salting step, curd was divided and salted with a concentration targeted to produce a final cheese with 600 mg of sodium/100 g (control), 25% reduced sodium (450 mg of sodium/100 g; both with and without KCl), and low sodium (53% sodium reduction or 280 mg of sodium/100 g; both with and without KCl). Potassium chloride was added on a molar equivalent to the NaCl it replaced to maintain an equivalent S/M. Cheese was inoculated with a 5-strain cocktail of L. monocytogenes at different times during aging to simulate postprocessing contamination, and counts were monitored over 27 or 50 d, depending on incubation temperature (12 or 5 °C, respectively). In cheese inoculated with 4 log10 cfu of L. monocytogenes/g 2 wk after manufacture, viable counts declined by more than 3 log10 cfu/g in all treatments over 60 d. When inoculated with 5 log10 cfu/g at 3mo of cheese age, L. monocytogenes counts in Cheddar cheese were also reduced during storage, but by less than 1.5 log10 cfu/g after 50 d. However, cheese with a 50% reduction in sodium without KCl had higher counts than full-sodium cheese at the end of 50 d of incubation at 4 °C when inoculated at 3 mo. When inoculated at 8 mo postmanufacture, this trend was only observed in 50% reduced sodium with KCl, for cheese manufactured with both cultures. This enhanced survival for 50% reduced-sodium cheese was not seen when a higher incubation temperature (12 °C) was used when cheese was inoculated at 3 mo of age and monitored for 27 d (no difference in treatments was observed at this incubation temperature). In the event of postprocessing contamination during later stages of ripening, L. monocytogenes was capable of survival in Cheddar cheese regardless of which culture was used, whether or not sodium had been reduced by as much as 50% from standard concentrations, or if KCl had been added to maintain the effective S/M of full-sodium Cheddar cheese.

Manufacture of reduced-sodium Cheddar-style cheese with mineral salt replacers.

The use of mineral salt replacers to reduce the sodium content in cheese has been investigated as a method to maintain both the salty flavor and the preservative effects of salt. The majority of studies of sodium reduction have used mineral salt replacers at levels too low to produce equal water activity (a(w)) in the finished cheese compared with the full-sodium control. Higher a(w) can result in differences in cheese quality due to differences in the effective salt-to-moisture ratio. This creates differences in biochemical and microbial reactions during aging. We hypothesized that by targeting replacer concentrations to produce the same a(w) as full sodium cheese, changes in cheese quality would be minimized. Stirred-curd Cheddar-style cheese was manufactured and curd was salted with NaCl or naturally reduced sodium sea salt. Reduced-sodium cheeses were created by blends of NaCl or sea salt with KCl, modified KCl, MgCl2, or CaCl2 before pressing. Sodium levels in reduced-sodium cheeses ranged from 298 to 388 mg of sodium/100g, whereas the control full-sodium cheese had 665 mg/100g. At 1 wk of age, a(w) of reduced-sodium cheeses were not significantly different from control, which had an a(w) of 0.96. The pH values of all reduced-sodium cheeses, excluding the treatment that combined sea salt and MgCl2, were lower than those of full-sodium cheese, indicating that the starter culture was possibly less inhibited at the salting step by the replacers than by NaCl. Instrumental hardness values of the treatments with sea salt were higher than in cheeses containing NaCl, with the exception of the NaCl/CaCl2 treatment, which was the hardest. Treatments with MgCl2 and modified KCl were generally less hard than other treatments. In-hand and first-bite firmness values correlated with the instrumental texture profile analysis results. Both CaCl2 and MgCl2 produced considerable off-flavors in the cheese (bitter, metallic, unclean, and soapy), as measured by descriptive sensory analysis with a trained panel. Bitterness ratings for cheese with KCl and modified KCl were not significantly different from the full-sodium control. Potassium chloride can be used successfully to achieve large reductions in sodium when replacing a portion of the NaCl in Cheddar cheese.

Determining salt concentrations for equivalent water activity in reduced-sodium cheese by use of a model system.

The range of sodium chloride (salt)-to-moisture ratio is critical in producing high-quality cheese products. The salt-to-moisture ratio has numerous effects on cheese quality, including controlling water activity (a(w)). Therefore, when attempting to decrease the sodium content of natural cheese it is important to calculate the amount of replacement salts necessary to create the same a(w) as the full-sodium target (when using the same cheese making procedure). Most attempts to decrease sodium using replacement salts have used concentrations too low to create the equivalent a(w) due to the differences in the molecular weight of the replacers compared with salt. This could be because of the desire to minimize off-flavors inherent in the replacement salts, but it complicates the ability to conclude that the replacement salts are the cause of off-flavors such as bitter. The objective of this study was to develop a model system that could be used to measure a(w) directly, without manufacturing cheese, to allow cheese makers to determine the salt and salt replacer concentrations needed to achieve the equivalent a(w) for their existing full-sodium control formulas. All-purpose flour, salt, and salt replacers (potassium chloride, modified potassium chloride, magnesium chloride, and calcium chloride) were blended with butter and water at concentrations that approximated the solids, fat, and moisture contents of typical Cheddar cheese. Salt and salt replacers were applied to the model systems at concentrations predicted by Raoult's law. The a(w) of the model samples was measured on a water activity meter, and concentrations were adjusted using Raoult's law if they differed from those of the full-sodium model. Based on the results determined using the model system, stirred-curd pilot-scale batches of reduced- and full-sodium Cheddar cheese were manufactured in duplicate. Water activity, pH, and gross composition were measured and evaluated statistically by linear mixed model. The model system method accurately determined the concentrations of salt and salt replacer necessary to achieve the same a(w) as the full-sodium control in pilot-scale cheese using different replacement salts.