Effects of Metal Ions and Gluconate on Surface Residues on Returnable Bottles
MBAA TQ vol. 39, no. 1, 2002, pp. 7-12 |
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Peer-Reviewed Paper
R. Alex Speers (1), Roberta C. Cameron
(2), Allan T. Paulson (1), Feridun Hamdullahpur (3), and William F.
Caley (4). 1. Department of Food Science and Technology, Dalhousie University, P.O. Box 1000, Halifax, NS, Canada B3J 2X4. 2. Edmonton, AB. 3. Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON. 4. Department of Mining and Metallurgical Engineering, Dalhousie University, Halifax, NS. This paper was originally presented in part at the World Brewing Congress, Orlando, FL, 2000.
Abstract
When returnable beer bottles are cleaned, a white surface residue or film sometimes forms. Typically, bottles are cleaned in a bottlewasher containing 3-5% NaOH or caustic. The residue appears to be related to factors such as the type of bottlewasher (soaker) used, operational down time, and the type and quantity of dissolved and suspended solids and ion concentration in the caustic solution. A model caustic soaker solution containing sodium hydroxide, sodium carbonate, and sodium hexametaphosphate was formulated with either distilled (soft) or municipal (hard) water, and the effects of dissolved metal ions (aluminum and silicon) and the amount of sequestrant (gluconate) on film formation were determined. Films were made on new glass bottles and glass microscope slides under simulated soaker time/temperature conditions and examined for appearance by visual inspection and reflection spectrophotometry. Metal ion levels were determined by atomic absorption spectrophotometry, and film microstructure of one treatment was examined by scanning electron microscopy. The results showed that surface films could be successfully simulated in the laboratory. Film appearance and microstructure were significantly affected by solution composition. The effect of gluconate on film appearance and composition depended on gluconate concentration and the type of water and metal ions present in the caustic solution.
Keywords: bottle films, caustic bottlewasher, soaker
Sintesis
Cuando se limpian botellas retornables de cerveza, a veces se forma un residuo o capa blanca en la superficie de la botella. Las botellas se lavan t�picamente en una lavadora con 3-5% sosa c�ustica (NaOH). El residuo aparentemente se relaciona con diferentes factores, tales como el tipo de lavadora usado, el tiempo de paradas operacionales, el tipo y cantidad de s�lidos disueltos o suspendidos y la concentraci�n de iones en la soluci�n c�ustica. Se prepar� una soluci�n de limpieza con sosa c�ustica, carbonato de sodio y hexametafosfato de sodio, tanto en agua destilada (suave) como en agua municipal (dura), y se determin� el efecto de los iones met�licos (aluminio y silicio) disueltos y la concentraci�n de secuestrante (gluconato) en la formaci�n de la capa. Se formaron capas en botellas de vidrio nuevas y en portaobjetos de microscopio (en condiciones simulando los tiempos y temperaturas reinantes en una lavadora) y se examin� la apariencia visualmente y por espectrofotometr�a de reflectancia. Los niveles de iones met�licos fueron determinados por espectrofotometr�a de absorci�n at�mica, y la microestructura de la capa de uno de los tratamientos fue examinado usando el escaneado por microscop�a de electrones. Los resultados demostraron que las pel�culas de la superficie podr�an ser simulados con �xito en el laboratorio. La apariencia de la capa y su microestructura fueron afectadas significativamente por la composici�n de la soluci�n. El efecto del gluconato sobre la apariencia de la capa, y su composici�n, depende de la concentraci�n del gluconato y el tipo de agua e iones met�licos presentes en la soluci�n c�ustica.
Palabras claves: Capas sobre botellas, lavadora de botellas
