Toward an Understanding of Mechanisms Involved in Non-Polyphenol Oxidase (Non-PPO) Darkening in Yellow Alkaline Noodles (YAN)
| Autor: | Robert E. Asenstorfer, Marie J. Appelbee, Daryl J. Mares, Christine A. Kusznir |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
chemistry.chemical_classification
Ethanol Flour fungi Wheat flour Color food and beverages General Chemistry Hydrogen-Ion Concentration Chemical reaction Polyphenol oxidase Tropolone Kinetics chemistry.chemical_compound Enzyme chemistry Biochemistry Enzyme Stability Cultivar Methanol Food science General Agricultural and Biological Sciences Catechol Oxidase Triticum Plant Proteins |
| Zdroj: | Journal of Agricultural and Food Chemistry. 62:4725-4730 |
| ISSN: | 1520-5118 0021-8561 |
| DOI: | 10.1021/jf500206e |
| Popis: | Asian noodles prepared from bread wheat flour darken over time due to a combination of polyphenol oxidase (PPO) activity and non-PPO effects. Although the enzymatic mechanism associated with the PPO reaction is well established, the non-PPO component consists of both physical (e.g., changes in surface properties) and chemical reactions. Variations in pH and solvents were used to gain a quantitative estimate of the contribution of physical and chemical components to non-PPO darkening in yellow alkaline noodles (YAN). In a set of five common high-PPO Australian wheat cultivars it was estimated that on average non-PPO darkening accounted for 69% of total darkening, with approximately two-thirds of this due to physical darkening and one-third had a chemical origin. Data from the chemical portion of non-PPO darkening is consistent with the presence of a PPO-like enzyme that oxidizes tyrosine, has a pH maximum of 8.1, and is inhibited by 50% methanol or ethanol but in the noodle is insensitive to PPO inhibitors such as tropolone. Therefore, with low-PPO and PPO-free wheat varieties becoming available, it may be possible to further reduce darkening in YAN by breeding for wheat varieties with low or zero levels of this PPO-like enzyme. |
| Databáze: | OpenAIRE |
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