Calcium and lactate are present in excess of their solubility in Cheddar cheese. Consequently, calcium lactate crystals are a common defect in Cheddar cheese. A novel approach for preventing calcium lactate crystals is the addition of sodium gluconate. Sodium gluconate has the potential to increase the solubility of calcium and lactate by forming soluble complexes with calcium and lactate ions, and preventing them from being available for the formation of calcium lactate crystals. This research project was to determine the efficacy of sodium gluconate as a calcium lactate crystal inhibitor in Cheddar cheese. The first part of this study was to determine if sodium gluconate could increase the solubility of calcium lactate. Seven calcium lactate solutions (5.31% w/w) with seven levels of sodium gluconate (0, 0.5, 1, 1.5, 2, 3, and 4% w/w) were made in triplicate. Solutions were stored at 7°C for 21 days, and were visually inspected for calcium lactate crystal formation. Subsequently, they were filtered to remove calcium lactate crystals and the supernatant was analyzed for lactic acid and gluconic acid by HPLC and for calcium by Atomic Absorption Spectroscopy. The visual inspection demonstrated that calcium lactate crystals were formed in the solution with 0% gluconate after the first day of storage and calcium lactate crystals continued to accumulate over time. A minute amount of calcium lactate crystals was also visible in the solution with 0.5% gluconate after 21 days of storage, while calcium lactate crystals were not visible in the other solutions. The HPLC results indicated that there was a higher concentration of calcium and lactic acid in the filtrate from the solutions containing added gluconate. Thus, sodium gluconate can increase the solubility of calcium lactate.
The second part of this study was to determine the manufacture and composition of Cheddar cheeses with different levels of sodium gluconate addition. Six Cheddar cheeses with two levels of salting (2 and 2.5%) and three sodium gluconate addition levels (0, 0.5 and 1%) were manufactured. All cheeses were made using a stirred-curd procedure and replicated three times. Two levels were obtained by dividing cheese curd (at pH 5.6) into two equal-weight halves; each half was salted with 2 and 2.5% (by weight of cheese curd) sodium chloride. Subsequently, each of the salted halves was separated into three equal-weight batches and mixed with 0 (control), 0.5, and 1.0% sodium gluconate, respectively. After sodium gluconate addition, the curds were hooped, pressed for 16 hour, vacuum-sealed in polyethylene bags, and transferred to a ripening room at 6 to 8°C. After 1 week of storage, compositional analyses (pH, moisture, salt, fat and protein) and gluconic acid concentration were determined. Mean pH, moisture, salt, fat and protein content of the cheeses ranged from 5.06 to 5.32, 36.98 to 38.15%, 1.65 to 2.13%, 30.96 to 32.98%, and 25.6 to 26.1%, respectively. At both salting levels, the pH and moisture contents were significantly (p<0.05) increased in the treatments with added sodium gluconate. The concentration of gluconic acid in the low salt treatments was 0.33 and 0.59% for the 0.5 and 1.0% addition level, respectively, whereas the concentration in the high salt levels was 0.33 and 0.58%, respectively.
The third part of this study was to determine if the level and type of residual sugar and organic acids produced during ripening was impacted by sodium gluconate addition to Cheddar cheeses. Six cheeses with two salting rates (2 and 2.5%) and three sodium gluconate addition levels (0, 0.5 and 1%) were manufactured. The cheeses were analyzed for lactose and water-soluble organic acids (acetic, butanoic, citric, formic, gluconic, lactic, orotic, propanoic, and uric) at 1-week, 3-month and 6-month, 9-month, and 12-month of ripening by using a cation-exchange-column HPLC externally equipped with a refractive index detector . The organic acids were detected using the UV detector set at 210 and 285 nm, and the refractive index was used for quantification of lactose. The results indicated that at 1-week of ripening, Cheddar cheeses with a higher concentration of gluconic acid had lower concentration of lactic acid, but higher concentration of lactose, while there were no differences in acetic, butanoic, citric, formic, orotic, propanoic and uric acids among treatments at all ripening times. The concentrations of butanoic and propanoic acids gradually increased over time in all treatments, whereas the concentrations of orotic acid and lactose gradually decreased over time. Minor changes in the levels of acetic, citric, formic, lactic, and uric were also observed throughout ripening in all treatments.
The fourth part of this study was to determine the effect of sodium gluconate on pH, lactose, lactic acid, and WSC changes during Cheddar cheese ripening. Six Cheddar cheeses with two salting levels (2 and 2.5%) and three sodium gluconate levels (0, 0.5 and 1%) were manufactured in triplicate. Composition and chemical analysis was performed at 1 week of ripening, and at 3, 6, 9, and 12 months of ripening. Cheeses were analyzed for pH, lactose and lactic acid, and WSC. Compositional analyses at 1 week indicated that sodium gluconate addition had a significant effect on cheese pH, moisture, Na, lactose, and lactic acid. Cheddar cheeses from both 2% and 2.5% salt levels with 0.5 and 1.0% sodium gluconate exhibited higher pH than the control cheeses throughout the ripening time. HPLC results from Cheddar cheeses from both 2% and 2.5% salt levels indicated that cheeses with higher concentration of sodium gluconate addition had a higher concentration of lactose, but lower concentration of lactic acid when compared to the control cheeses throughout the ripening time. WSC results indicated that Cheddar cheeses from both 2% and 2.5% salt levels with higher concentration of sodium gluconate addition had lower WSC concentration when compared to the control cheeses throughout the ripening time. From the results, we concluded that sodium gluconate could have an effect on starter culture activity and could also act as buffering agent, which would cause a higher cheese pH. A higher cheese pH resulted in less soluble of calcium in the cheese serum; thus, resulting in less calcium and lactate ions in the cheese serum.
The final part of this study was to determine the effect of sodium gluconate on the extent of proteolysis, textural properties and sensory evaluation during Cheddar cheese ripening. Six Cheddar cheeses with two salting levels (2 and 2.5%) and three sodium gluconate levels (0, 0.5 and 1%) were manufactured in triplicate. Cheeses were analyzed for the extent of proteolysis by measuring pH 4.6 soluble N and 12% TCA soluble N at 3, 6, 9, and 12-month of ripening. Textural properties were determined by Texture Profile Analysis (TPA) using a TA.XTplus Texture Analyzer at 3, 6, 9, and 12-month of ripening. TPA parameters generated were fracturability, hardness, cohesiveness, springiness, chewiness, and resilience. Descriptive sensory analysis was used to monitor Cheddar cheese flavors in this study at 6 and 12-month of ripening. An increase in soluble N and decreases in textural properties (fracturability, hardness, cohesiveness, springiness, gumminess, chewiness, and resilience) were observed throughout the ripening time for all treatments. At both salting levels, cheeses with added sodium gluconate exhibited a trend for a higher level of proteolysis and lower TPA hardness at 6 and 9 months. The overall flavor intensity scores at 6 months of ripening were lower in cheeses with added sodium gluconate, which could relate to their lower bitterness scores. A similar trend was observed at 12 months of ripening, where cheeses with sodium gluconate addition had lower overall flavor intensity and lower bitterness scores. This present study provides an understanding of how sodium gluconate impacts cheese characteristics during ripening.
University of Minnesota Ph.D. dissertation. August 2011. Major: Food science. Advisor: Dr.Lloyd Ernst Metzger. 1 computer file (PDF); xvii, 265 pages.
The efficacy of sodium gluconate as a calcium lactate crystal inhibitor in Cheddar cheese..
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