Modification of the Neutral-Detergent Fiber Procedure for Cereals and Vegetables by Using α-Amylase

Abstract

Samples with a high starch content that were incubated at 40°C overnight (12-18 hr) in pH 7 buffer with bacterial α-amylase before determination of their neutral-detergent fiber (NDF) contents were easier to filter and had lower estimates of NDF and hemicellulose than when the conventional procedure was used. At neutral pH, bacterial a-amylase was more effective in this role than 2 common fungal amylase preparations. Pretreatment with pepsin at pH 1.8 also reduced the estimates of NDF content but some samples still proved difficult to filter. Bacterial α-amylase that was added during the initial step of the ccnventional procedure exhibited some activity even after boiling in neutral-detergent reagent for 30 min and promoted rapid filtration of the samples, but led to estimates that were higher than those obtained following overnight incubation at 40°C. The reported modification of incubating samples overnight with α-amylase promotes rapid filtration, and thereby gives more accurate NDF estimates and less analytical variation for samples of cereal grains and vegetables that have a high starch content.