The effect of the antarctic krill (Euphausia superba) chitin as a dietary fiber on the availability of protein and minerals (Ca, Mg and P) was studied in growing rats fed diets containing 5% krill chitin, lobster (Panulirus gracilis) chitin or cellulose for 10 days. The chitins were prepared by the modified Hackman's method (the treatment with 1 N HCl and 1 N NaOH and the following extraction by acetone) from the frozen blocks of raw krill or the shells of boiled and frozen lobster.
Total nitrogen and ash contents of both the purified chitins were 6.82% and 0.1%, respectively.
The settling volume in water (SV, ml/g) of the examined dietary fibers was 35.0 for krill chitin, 12.0 for lobster chitin and 3.4 for cellulose.
There were no differences in the net protein ratio and retention rate of dietary nitrogen (excluding chitin nitrogen), between krill chitin and the other two dietary fibers.
The most deteriorating effect of the dietary fibers on the mineral balances was observed for krill chitin, followed by lobster chitin. High correlation, |r|=0.707-0.943 (p<0.01), was found between each of the mineral balances (fecal, urinary and total excretion, apparent digestibility, retention and retention rate of the three minerals except urinary P excretion) and the log SV of each dietary fiber. These results show that the effect of krill chitin as a dietary fiber on the bioavailability of minerals can be partly ascribed to its high SV.