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A flow-based platform for measuring the acidity parameters in wine

Publication . Vidigal, Susana S. M. P.; Rangel, António O. S. S.

The present work describes a valuable tool for winemaking industry to measure the acidity parameters with rapid response, simple sample handling, with no or minimal pre-treatment. Thus, a sequential injection analysis (SIA) system with spectrophotometric detection was used as platform for the development of methodologies for the quantification of volatile and total acidity in wine samples. Both procedures make use of the same colour reagent, bromothymol blue (BTB) that changes its intrinsic colour in the presence of the acidity compounds. The volatile acidity value was attained with the separation of the volatile fraction of acids by means of a membrane separation technique, a gas-diffusion unit. For the total acidity value, the sample was merged with the colour reagent on the way towards detection. The fixed acidity is a result of the difference from the total and the volatile acidity. The presented tool displayed a low sample and reagent consumption, 346 and 102 µL of sample and 37 and 32 µg of BTB, for the volatile acidity (VA) and for the total acidity (TA), respectively. The observed limits of detection and quantification were 0.03 and 0.01 g L−1 (VA) and 0.09 and 0.02 g L−1 (TA) with high determination rates, 35 (VA) and 62 (TA) determinations per hour. The proposed system was successfully applied to the quantification of volatile, total and fixed acidity in white table wine samples. The obtained results were in good agreement with the ones obtained by the reference methods.

2017Journal article

Restricted access

A reagentless flow injection system for the quantification of ethanol in beverages based on the schlieren effect measurement

Publication . Vidigal, Susana S.M.P.; Rangel, António O. S. S.

A flow injection system comprising a gas-diffusion unit and schlieren effect detection was arranged in order to develop a simple methodology for the quantification of ethanol in different alcoholic beverages. It was possible to establish a linear range up to 25% (v/v), with a LOD and a LOQ of 0.6% and 2.0% (v/v), respectively; with good repeatability, RSD < 4.6%. Only 80 mu l. of sample was needed for quantification with a determination rate of one determination per minute. To evaluate the accuracy of the proposed method, a total of 43 alcoholic beverages, red and white table wine, port wine, beers, liquors, spirits and brandies were analysed. The results obtained by the developed method were in good agreement with the ones obtained by the reference method.

2015Journal article

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Determination of total protein content in white wines by solid phase spectrometry in a SI–LOV system

Publication . Vidigal, Susana S. M. P.; Tóth, Ildikó V.; Rangel, António O. S. S.

Although present at low concentration in wine samples, proteins, have considerable technological importance, due to their capability of haze formation. The present work presents a methodology for the quantification of total protein in white wine in a sequential injection lab-on-valve system, exploiting the bead injection concept for solid phase extraction with spectrophotometric detection. The method is based on the retention of the proteins in the solid support, NTA (nitrilotriacetic acid) superflow beads, charged by Cu2+. The change in the absorbance is monitored at 500 nm at the surface of the beads after addition of the Folin–Ciocalteu’s reagent (FCr). The developed method presented a sample consumption of 400 L per assay and a consumption of FCr and Cu2+ solution of 25 L and 100 L per assay, respectively. It was possible to achieve a linear range up to 0.30 g/L with a limit of detection and quantification of 0.03 and 0.10 g/L, respectively. The proposed method was successfully applied to white wine samples.

2012Conference object

Restricted access

A flow system for the quantification of ethanol in beverages based on shlieren effect measurement

Publication . Vidigal, Susana S. M. P.; Rangel, António O. S. S.

2014Conference object

Open access

Monitoring a Dynamic System with a Low Pressure Liquid Chromatography System: Application to a Vinification Process

Publication . Vidigal, Susana; Rangel, António O. S. S.

2014Conference object

Open access