To evaluate functional component durability of valves and nozzles in cup-dispensing vending machines and drink dispensers, three thermoplastic resin types (linear low density polyethylene (LLDPE), polyoxymethylene (POM) and polyamide 612 (PA612)) used as such components were soaked in various syrups differing in ingredient composition (citric acid, ascorbic acid, ethanol, sucrose, and limonene) and the influence on resin physical properties and syrup taste were investigated. We found that syrups have the ability to alter the physical properties of the resin, such as tensile strength, elongation, and elasticity, while simultaneously, resins have a negative effect on syrup taste. In relation to LLDPE, swelling of the resin and a remarkable drop in tensile strength were observed in case of soaking in the syrup containing limonene. In the case of PA612, the physical properties of the resin underwent significant changes with respect to swelling, tensile strength, elongation and elastic modulus. POM soaked in ethanol showed swelling and lower elastic modulus. Furthermore, syrup taste changed considerably when in contact with POM for syrups containing both ethanol and citric acid. This study revealed the importance of choosing suitable resins for syrup ingredients to improve the durability of parts and quality of drinks.
Our previous report revealed the unpleasant taste found in beverage syrups after soaking polyoxymethylene (POM) into syrups containing citric acid and ethanol. Herein, we investigated both the compounds contributing to the unpleasant taste and the conditions upon which they form as a function of syrup type, which differ in citric acid and ethanol content. The molded POM was soaked in the testing syrup having varying concentrations of citric acid and ethanol. Thereafter, the soaked syrup was evaluated for taste unpleasantness by a sensory test employing variance analysis. The unpleasant taste resulted from mutual interaction of citric acid and ethanol in the syrup in the presence of POM. We analyzed the syrup by GC/MS, and evaluated the relationship between total ion chromatograph intensity of the detected compounds and taste rating for the syrup. Correlation of fatty acid and hindered phenol concentration with taste rating identified these compounds as a contributing factor of the unpleasant taste. Furthermore, the results evidenced that the unpleasant-tasting compounds were produced as a direct result of citric acid and ethanol interaction independent of the molecular weight and chemical composition of POM.
The polyetherurethane was composed by using poly (ethylene glycol) (PEG) and Lysine triisocyanate (LTI) and was provided at a high yield (90%). The polyetherurethane was characterized by thermal and mechanical properties. The thermal stability of the obtained polyetherurethane was measured by TGA, and the weight loss started at 290°C. The Young’s modulus of the obtained film taken from S-S curve was 63.2MPa. As a result of hydrolysis in phosphorus acid buffer solution (pH 8.4) as degradable examination, the obtained polyetherurethane was disintegrated into PEG and LTI.