A comparison of three methods for the determination of available lysine in barley

El-Sherbiny, A.E.; Draper, S. R.; Topps, J. H.

doi:10.1016/0377-8401(80)90009-7

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“…Replacing direct counting of protozoa cells by indirect AEP determination did not result in any marked improvement of the correlation of RNV with BV or NPU, but the modification avoids tedious cell counting in a haemocytometer and allows analyses to be done at any time. It may be usefully applied in the T. pyriformis assay of amino acid availability (Stott & Smith, 1966;Shorrock, 1976;El-Sherbiny, Draper & Topps, 1976).…”

Section: Discussionmentioning

confidence: 99%

2-Aminoethylphosphonic acid as an indicator ofTetrahymena pyriformisW growth in protein-quality evaluation assay

Maciejewicz-Rys

Antoniewicz

1978

Br J Nutr

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I. The concentration of 2-aminoethylphosphonic acid (AEP) in 96 h cultures of Tetrahymenapyriforrnis W was studied in order to apply it as an indicator in the assay of the relative nutritive value (RNV; protozoa population with test protein: protozoa population with whole-egg powder) of protein. Foodstuffs and food mixtures of different protein contents and qualities were used as test samples.2. RNV values based on AEP determination (RNVAxp) were compared with corresponding values calculated from protozoa counts (RNV,,), as well as with biological value (BV) and net protein utilization (NPU) of the same proteins assayed on rats.3. Both for foodstuffs and food mixtures highly significant correlations were found between RNVAEp and RNV,,, RNVAE~ and both BV and NPU, and RNV,, and both BV and NPU.4. AEP content in the protozoal suspension was preferred to cell count as a measure of growth response, since it took into account large differences in cell dimensions that were observed between cultures grown with different test proteins.The method for the evaluation of protein quality using the protozoon Tetrahymena pyriformis W (Fernell & Rosen, 1956) as modified by Stott, Smith & Rosen (1963) involves the determination of the number of protozoa organisms after incubation for 4 d in a medium containing the protein to be evaluated. The total number of protozoa cannot be measured turbidimetrically because many foodstuffs are insoluble and coloured.Total protozoa count, estimated using a haemocytometer, has often been made (Fernell & Rosen, 1956; Teunisson, 1961;Rosen, Stott & Smith, 1962;Stott et al. 1963; Baum & Haenel, 1965;Rslle & Eggum, 1971) but such a procedure is laborious and time-consuming (Teunisson, 1971 ;Shorrock & Ford, 1973). For many years, therefore, studies have been made of the potential use of other methods for protozoal population density determination.Teunisson (1971) proposed a method for counting the cells electronically with a Coulter Counter, after separating T. pyriformis W cells from food particles. Attempts to apply acidity determination (Rockland & Dunn, 1949) or a colorimetric method (Anderson & Williams, 1951; Viswanatha & Liener, 1955; Bergner, Munchow & Koch, 1968) in the measurement of growth responses gave poor results.Methods based on extinction measurements have been applied to alkaline extracts of soluble proteins (VoiiSek & Leitgeb, 1973) and to high-protein meals after treatment with papain (Shorrock & Ford, 1973), but they are not widely applicable.Shepherd, Taylor 84 JULITA M A C I E J E W I C Z -R Y S / AND ANNA M . ANTONIEWICZ foodstuffs and food mixtures, estimated both from protozoa counts in a haemocytometer and from AEP content. The results were also compared with biological value (BV) and net protein utilization (NPU) results determined with rats. MATERIALS A N D METHODS MaterialsThe foodstuffs tested were chosen to illustrate differences in quality within and between different protein sources. The samples comprised: fish meals (FM26, FM33, FM45, FM58), blood meals (...

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Section: Discussionmentioning

confidence: 99%