[Nutritional study of field bean protein isolate and of spun field bean protein-casein fibers]

[Absorption and use of differently structured protein isolates by rats]

Differently structured isolated proteins with the same amino acid composition were tested with growing albino rats in an N-balance and absorption experiment. The following items were tested: --isolated horse bean protein --hydrolysed isolated horse bean protein with an amino acid supplement to make up for losses due to hydrolysis --horse bean protein-casein (1:1) fibres --isolated horse bean protein with an amino acid supplement to achieve the same amino acid concentrations as in the horse bean protein-casein fibres. The lowest digestibility and utilisation values were ascertained for the hydrolysed protein. Endogenous N-excretion calculated according to the isotope dilution method was higher than for intact proteins, the transport of the chyme in the digestive tract and the true absorption of N in the small intestine had significantly diminished. In comparison with horse bean protein supplemented with amino acids, the horse bean protein-casein fibres showed decreased protein utilisation and increased endogenous N-excretion. Independent of the protein fed and of the time after feeding a relatively constant endogenous N-quota of approximately 70% could be ascertained in the chyme in the small intestine. In contrast to this, the relation between exogenous and endogenous N determined from the contents of the large intestine proved to be dependent on the intermediary utilisation of the protein fed.

[In vitro digestibility of original and modified protein isolate from faba beans]

Protein isolate from Vicia faba (API) and 18 different partial hydrolysates of API as well as plasteins produced from them were submitted to an in vitro digestion with pepsin and pancreatic proteases at their specific pH-optimum. By means of this technique a final value of hydrolysis (49,8 +/- 3,0)% was obtained with all investigated samples, in spite of the different intensity of the preliminary hydrolysis. Two samples with a degree of preliminary hydrolysis of 35% showed with 55% and 56%, respectively, a significantly higher final value. From the results may be assumed that by means of partial hydrolysis and plastein formation only such peptides will be formed which are again hydrolyzable in vitro.

[Formation of plastein gels from peptic digests of field bean protein isolates]

Peptic partial hydrolysates of a different hydrolysis degree were prepared from horse bean protein isolate and used for the plastein reaction with thermitase. Whilst unsoluble products were formed from partial hydrolysates of a hydrolysis degree above 60%, plastein gel could be obtained from a less intensely split basic material. By gel chromatography and by determination of the percentage which was unsoluble in 10% trichloroacetic acid, a proteolytic degradation could be made proof on the conditions of the plastein reaction. On addition of DL-methionine ethylesters to the partial hydrolysate an increasing incorporation of methionine into the plastein could be observed with increasing hydrolysis degree.

[Nutritional physiology studies in pigs on the evaluation of modified proteins. 1. Results of the estimation of N-turnover, apparent and true digestibility of proteins in addition to apparent and true absorption of amino acids in the entire digestive tract]

Sulfuric acid-casein (A), spray dried isolated Vicia faba protein (B), Vicia faba protein/casein (1 : 1) protein fibres-untreated (C), treated with dialdehyde starch (D) or aluminum chloride (E) and meal of Vicia faba (F) were studied as sole protein sources in semisynthetic feed mixtures on 13 female pigs (40 to 45 kg body weight). Total utilization of nitrogen (b-value, PNu) and intermediate utilization (BW) were highest in A, followed by C. Protein C was superior to D. Protein E showed a drastic drop in protein quality compared with D because of a high decrease in S-containing amino acids content, however, their efficiency (bc-1-value) was not limited. Despite of a higher apparent digestibility by approximately 17 units in protein B, proteins B and F showed a similar quality. The true absorption of cystine (estimated by the balance of digestive tract) was corresponding to the protein quality of the respective step of treatment of protein C and was used for the correction of the gross content is S-containing amino acids.