Accounting for co-extractable compounds (blank correction) in spectrophotometric measurement of extractable and total-bound proanthocyanidin in Leucaena spp

• Published in: Journal of the science of food and agriculture Vol. 82; no. 8; pp. 860 - 868
• Main Authors: Dalzell, Scott A, Kerven, Graham L
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.06.2002; Wiley
• Subjects: absorbance; anthocyanidins; Biological and medical sciences; blank correction; bound; butanol; co-extractable compounds; computer software; condensed tannin; extractable; fibre-bound; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; hydrochloric acid; insoluble; Leucaena; Leucaena magnifica; methodology; Methods of analysis, processing and quality control, regulation, standards; proanthocyanidin; protein-bound; temperature; Interference; Leucaena; Correction factor; Accuracy; Analysis method; Leguminosae; Dicotyledones; Angiospermae; Pigments; Anthocyanidin; Spermatophyta; Proanthocyanidin; Measurement method; Spectrophotometry
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/jsfa.1106

Methods to account for the spectral interference of co-extractable compounds (blank correction) in the spectrophotometric analysis of both extractable and bound proanthocyanidin (PA) using the proanthocyanidin (butanol/HCl) assay were evaluated. Crude extractable and bound PA sample matrices of PA-free Leucaena magnifica were used. Extractable PA blanks generated in heated 95% butanol/5% H2O reagent underestimated the optical density (absorbance) of co-extractable compounds by 24% (P < 0.01), whereas unheated 95% butanol/5% HCl blanks, incubated at room temperature, accurately measured the absorbance of the background matrix (P < 0.01). Current procedures that estimate bound PA concentrations using the proanthocyanidin assay produce intensely coloured background matrices. Recovery measurements from total-bound PA extracts spiked with 1071 and 2142 µg anthocyanidin per tube indicated that existing analytical procedures that do not account for the spectral interference of co-extractable compounds overestimated (P < 0.01) bound PA concentrations by 69 and 38% respectively. An innovative technique that generated an internal correction factor for each sample, using wavelength-scanning spectrophotometry and non-linear curve-fitting computer software, was developed. This procedure recovered 100% of added anthocyanidins from bound PA matrices.