Quality control of beer hopped with reduced isomerised products

The traditional method for measuring bitterness in beer by UV absorbance (ASBC9.6) remains a viable quality control method for normally hopped beer. However, after reduction of isoalpha acids specific absorptivity of active components change and HPLC analysis showns to be a reliable method for quality control of these materials. This work is intended to adapt mathematically the ASBC(American Society of Brewing Chemist) spectrophotometrical method and to evaluate an HPLC method to control composition of different commercial reduced isomerised products added to unhopped wort and partially kettle hopped beer. The results we obtained showed that the HPLC method is reliable for quality control of reduced isomerised products and that the traditional spectrophotometrical method is viable for quality control of beer, also using reduced isomerised products as far as an adequate factor is used.

Efeito da maltagem e da extrusäo termoplástica sobre a qualidade tecnológica da cultivar de soja Br 16 / Effect of malting and thermoplastic extrusion on the technologic quality of the derived product of soybean

Sementes de soja cultivar BR 16 foram submetidas à maltagem por 24 e 48 horas e à extrusao obtendo-se flocos, os quais foram moídos e utilizados na fabricaçao de biscoitos. Flocos e biscoitos foram analisados sensorialmente. O efeito da maltagem e da extrusao foram também avaliados em relaçao às características químico-nutricionais. A composiçao em macro nutrientes nao apresentou alteraçoes acentuadas mostrando pequeno decréscimo nos teores de carboidratos totais e discreto aumento relativo nos teores de carboidratos totais e discreto aumento relativo nos teores de lipídeos no produto maltado. Dentre os fatores antinutricionais, os inibidores de tripsina apresentaram queda de 50 por cento após 24h de maltagem e desaparecimento após a extrusao. Os teores de ácido fítico nao sofreram variaçao expressiva, enquanto que os alfa-galactosídeos apresentaram decréscimo de até 80 por cento com os processos combinados de maltagem e extrusao.

Application of high performance liquid chromatography to the analysis of some non-volatile coffee components

High performance liquid chromatography (HPLC) was applied to the analysis of caffeine, trigonelline, nicotinic acid and sucrose in Arabica an Robusta coffee. Green and roasted coffee samples were used in this study and the degradation of sucrose and trigonelline, with the formation of nicotinic acid, was followed during roasting. Caffeine did not undergo significant degradation with only 5.4% being lost under severe roasting. Sucrose was degraded rapidly during processing with light roasting producing a 97% loss and dark roasting degrading it completely. Loss of trigonelline was strongly dependent on the degree of roasting being higher in the Robusta coffee. Trigonelline degradation was associated with nicotinic acid formation both in the Arabica and Robusta coffees as a consequence of the roasting process. Trigonelline and sucrose were determined simultaneously by partition chromatography and detection with the mass detector. Determination of caffeine was carried out using reversed phase chromatography and nicotinic acid by ion-pair reversed phase chromatography. Detection in both cases was achieved using an ultraviolet detector at 272nm or 254nm, respectively. HPLC showed adequate precision and accuracy for routine analyses. In addition, the methods used were more rapid and simple than traditional procedures. HPLC appears to be a suitable technique for quality control in the coffee industry, and for fundamental investigation on the mechanisms involved in the roasting process (AU) s

Efeito da torrefaçäo no perfil cromatográfico obtido por filtraçäo em gel de extratos de café Arábico / Effect of roasting on the chromatographic profile obtained by gel filtration of Arabian coffee extract

As modificaciones que ocorrem durante a torrefaçäo do café, em relaçäo aos pesos moleculares de seus componentes, foram estudadas, usando-se cromatografia de filtraçäo em gel com colunas do tipo TSK-pW400, sob alta pressäo. Os extratos obtidos de amostras de café verde e torrado em diferentes intensidades foram cromatografados e monitorizados usando-se detectors de índice de refraçäo diferencial (IRD) e de ultra violeta (UV) a 280, 325 e 410nm. Marcantes diferenças foram verificadas nos cromatogramas dos extratos, usando-se o detector IRD, em relaçäo ao café verde e ao café torrado em diferentes intensidades. O uso do detector de UV a 280nm e 325nm mostraram similaridades no perfil cromatogrâfico, indicando que a formaçäo de componentes de alto peso molecular, durante a torrefaçäo, envolve a participaçäo de ligaçöes entre proteínas e compostos fenólicos. A formaçäo de pigmentos pode ser claramente acompanhada durante a torrefaçäo com detecçäo a 420 nm. O uso de cromatografia líquida de alta resoluçäo provou ser um método extremamente rápido, em comparaçäo a filtraçäo em gel tradicional, mostrando-se útil para estudos mais detalhados das modificaçöes de pesos moleculares que ocorrem durante o processo de torrefaçäo do café