Low frequency ultrasonic-assisted hydrolysis of starch in the presence of α-amylase.

Hydrolysis of starch is an important process in the food industry and in the production of bioethanol or smaller carbohydrate molecules that can be used as starting blocks for chemical synthesis. Such hydrolysis can be enhanced by lowering the pH, heating the reaction mixture or catalyzing the reaction with enzymes. This study reports the effect of sonication on the reaction rate of starch hydrolysis at different temperatures, in the presence or absence of alpha-amylase. Starch Azure, a commercially available potato starch covalently linked with Remazol Brilliant Blue, has been chosen since its hydrolysis releases a blue dye, which concentration can be monitored by UV Vis spectroscopy. Ultrasounds, regardless of experimental conditions, provide the highest reaction rate for such hydrolysis.

Temperature effect on an ultrasound-assisted paper de-inking process.

The influence of temperature on an ultrasound-assisted ink removal process has been investigated. White copy paper was evenly soaked in black writing ink. After drying the paper to constant weight at 75 degrees C, ink removal was attempted under varying conditions. Results were assessed by monitoring the UV-vis absorbance of the aqueous phase and measuring the brightness of the paper. Sonication was observed to improve the brightness of the paper in the temperature range of 15-45 degrees C with an optimum effect at 35 degrees C. Monitoring UV-vis spectra of the aqueous phase provided evidence that modification of the chemical structure of the ink desorbed from the paper occured. Further investigation under the same conditions showed that ink, when not absorbed on paper, did not undergo the same chemical change. This supports the hypothesis that only the compound released from the ink absorbed onto the paper is sensitive to sonodegradation. One possible explanation is that the metal binding component of the ink stays absorbed on the paper, releasing the organic part, whose chemical structure can be altered by the effect of sonication. Inductively coupled plasma analysis was used to confirm that during the de-inking process of the paper, the metal binding component stays absorbed on the paper and only the organic part is released in the aqueous phase.