University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Food -> jam

Citations 3

"A Continuous Spectrophotometric System For The Discrimination/determination Of Monosaccharides And Oligosaccharides In Foods"
Anal. Chim. Acta 2000 Volume 404, Issue 1 Pages 121-129
A. Cáceres, S. Cárdenas, M. Gallego and M. Valcárcel

Abstract: A simple, rapid method for the spectrophotometric discrimination of monosaccharides from the oligosaccharide fraction of fruit juice, jam, syrup and honey samples is proposed. The sample, in alkaline medium, is directly introduced into a flow system and passed through an activated carbon column for its decolorization; then, a volume of 200 µl is injected into the derivatising reagent stream to start the analytical reaction, which takes place at 85°C. The two fractions are discriminated on the basis of the different colors of the derivatives formed; thus, the derivatives of the monosaccharides are yellow while those of the di- and trisaccharides are violet-carmine. The two fractions are monitored at 400 and 540 nm, respectively. Sucrose gives no reaction as it is a non-reducing sugar. The proposed method allows reducing sugars contents from 0.01% to 0.80% w/v to be determined with an average relative standard deviation of 4.5% and a sampling frequency of 10 h-1. The proposed method was validated by applying it to two milk-based and sugar candidate artificial CRMs, with good correlation. The detection limits achieved (0.01% w/v for maltose, lactose and maltotriose at 540 nm) allow adulteration of fruit juices with high fructose syrup from starch at the 4% level to be detected.
Monosaccharides Oligosaccharides Maltose Lactose Maltotriose Spectrophotometry Reference material Heated reaction Activated carbon Column

"Spectrophotometric Flow Injection Determination Of Ascorbic Acid By Generation Of Triiodide"
Anal. Chim. Acta 1986 Volume 184, Issue 1 Pages 243-250
J. Hernández-Méndez, A. Alonso Mateos, M. J. Almendral Parra and C. García De María

Abstract: Tri-iodide and its starch complex were generated in a flow injection system of three channels containing (a) 0.08 M KI plus 1.20 g L-1 of starch, (b) 46 µM-KIO3 in 1 mM H2SO4, and (c) carrier solution (pH 1.5 to 11.0), at flow rates of 1.5, 1.5 and 3.0 mL min-1, respectively; I3- and the starch complex were detected at 350 and 580 nm, respectively, and ascorbic acid(I) was measured as a negative peak. The range of rectilinearity depended on the concentration. of KIO3 and I was determined at concentration. of 0.1 to 40 µg L-1 with coefficient of variation of 1.5 to 8.0%. Results for different samples compared well with those obtained by titrimetry. The method has been applied to pharmaceutical preparations and fruit juice and jam containing vitamin C.
Ascorbic acid Spectrophotometry Method comparison

"Spectrophotometric Determination Of Glucose In Foods By Flow Injection Analysis With An Immobilized Glucose Oxidase Reactor"
Z. Lebensm. Unters. Forsch. 1997 Volume 204, Issue 2 Pages 99-102
Renbing Shi, Kathrin Stein, G. Schwedt

Abstract: Samples, e.g., apple juice or banana jam were diluted up to 100-fold with 50 mM phosphate buffer of pH 5. Portions (0.1 ml) were injected into the carrier stream (1.3 ml/min) of 0.5% KI in the same buffer. The carrier stream passed through the immobilized glucose oxidase reactor (4.5 cm x 2 mm i.d., preparation described). The H2O2 formed and the KI were mixed with a catalyst solution (0.6 ml/min) of 0.06% starch and 0.006% ammonium heptamolybdate in 0.1 M H2SO4 and, after a stopped-flow delay of 20 s, the absorbance was measured at 620 nm. The calibration graph was linear for 0.1-2 mM glucose. The RSD (n = 5) was 1.6% at 1 mM. Because of the high dilution, there was no interference from ascorbic acid. If the reactor were stored in the buffer at 4°C between measurements it could be used for up to 200 determinations during one month. The results presented were in good agreement with those obtained by a standard enzymatic method.
Glucose Spectrophotometry Reactor Method comparison Interferences Stopped-flow Catalysis Immobilized enzyme