Progress 10/01/04 to 09/30/06
Outputs
The purpose of this project was to increase the understanding of how food product composition impacts chemical stability. These compositional effects were demonstrated in one experiment by evaluating the stability of thiamin in solution as a function of pH, buffer type, and buffer concentration. Thiamin stability decreased as pH increased and as buffer salt concentration increased. At pH 6 and 7, degradation was faster in phosphate buffer than citrate buffer. However, at pH 4 and 5, degradation was faster in citrate buffer. Differing degradation mechanisms at the various pH levels and differing catalytic effects of buffer types explain these results. Also in solutions, adding sucrose or glycerol to a glucose/glycine mixture enhanced the Maillard reaction (i.e., glucose loss and browning) due to the humectants (i.e., sucrose or glycerol) removing water as the reaction product. Such humectants are often viewed as food stabilizers, but not in this case. Compositional
effects can also influence stability within solids, as was demonstrated by the effect of polyols on the thermal unfolding of gelatin. Some molecules, like glycerol, made gelatin more sensitive to heating in comparison to other molecules, like trehalose. The differences in thermal stability between formulations have been attributed to differences in the amorphous states (i.e., glass transition temperatures) of the protein systems. These experiments demonstrate how simple changes to the composition of a food can benefit or harm its chemical stability.
Impacts
Food manufacturers must be aware of stability issues associated with the composition of their food products so that the characteristics of the food will be maintained. Changing a formulation to include different buffer salts or different humectant types can, upon occasion, have serious effects on the shelf life of food and consequently reduce the food's acceptability to consumers.
Publications
- Pachapurkar, D. and Bell, L.N. 2005. Storage stability of thiamin in solution as affected by pH, buffer type, and buffer concentration. 2005 IFT Annual Meeting Book of Abstracts. Chicago: Institute of Food Technologists. 99B-4.
- Bell, L.N. and Chuy, S. 2005. Catalytic effect of humectants on the Maillard reaction. 2005 IFT Annual Meeting Book of Abstracts. Chicago: Institute of Food Technologists. 99B-12.
- Chuy, S. and Bell, L.N. 2006. Buffer pH and pKa values as affected by added glycerol and sucrose. Food Research International, 39:342-348.
- Bell, L.N. 2007 (actually available in 2006). Nutraceutical stability concerns and shelf life testing. Ch. 25, in Handbook of Nutraceuticals and Functional Foods, 2nd edition, R. Wildman, ed. Boca Raton, FL: Taylor & Francis Group. pp. 467-483.
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Progress 01/01/05 to 12/31/05
Outputs
This project's initial study evaluated the stability of the vitamin thiamin as a function of product composition. Thiamin is being incorporated into various nutritionally-enhanced beverages, but data on its storage stability are lacking. The stability of thiamin was studied in various beverage-like solutions. The effects of pH, buffer type, and buffer concentration were evaluated at room temperature. Thiamin is least stable at pH 7; as pH decreases, stability increases. As the concentration of the buffering salts increases, the thiamin degradation increases. Buffer salts act as catalysts for its degradation. At pH 6 and 7, degradation is faster in phosphate buffer than citrate buffer. However, at pH 4 and 5, degradation is faster in citrate buffer. Differing degradation mechanisms at the various pH levels and differing catalytic effects of buffer types explain these results.
Impacts
Manufacturers of thiamin-containing beverages can increase the shelf life of their products by selecting the appropriate buffer type at its lowest possible concentration, based on the pH of the beverage. In a dairy-type beverage containing thiamin at pH 7, for example, approximately four times less thiamin will be lost by using citrate rather than phosphate buffer. Better thiamin retention in foods translates into the delivery of better nutrition to consumers.
Publications
- Pachapurkar, D. and Bell, L.N. 2005. Kinetics of thiamin degradation in solutions under ambient storage conditions. J. Food Sci. 70(7): C423-426.
- D'Cruz, N.M. and Bell, L.N. 2005. Thermal unfolding of gelatin in solids as affected by the glass transition. J. Food Sci. 70(2): E64-E68.
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