Availability of sulphur amino acids in protein foods

Abstract

EXPERIMENTALPreparation of the materials Freeze-dried cod muscle. This was cod muscle, i.e. fillets, that had been preheated in a commercial steam cabinet at 99' for 4-5 min, pressed to remove aqueous liquors, freeze-dried by an accelerated process and packed in cans under N,. In the laboratory, the resulting cod flake was hammer-milled to a coarse powder, gas-packed in ' oxygenfree' N, and held at -1 0 ' . (It was thus similar to the material used by Carpenter et al. (1957) except for the initial steaming and pressing.)One portion was reground to pass a 60-mesh sieve, then used for preliminary experiments in which small samples were heated in sealed glass ampoules. In the light of these results, certain heat treatments were selected and applied to the coarsely ground starting material in sealed cans in sufficient quantity for the main experiments, including animal feeding trials.Addition of glucose. When required a solution of D-glucose was added to cod-muscle powder in the proportion of either 5 parts glucose to 95 parts cod dry-matter or in the proportion of 10 to 90 parts respectively to form a slurry. After thorough mixing, the slurry was freeze-dried and reground. Adjzlstment of moisture content. A portion of the finely ground cod muscle was further dried by heating at greatly reduced pressure over P,O, for 24 h at 37' and then for 18 h at 7 0 ' . This material was used for studies of heating for 27 h at I 15' and for 729 h at 85". A second portion was dried, along with a sample of 'codfglucose' powder by standing over P,05 in an evacuated desiccator at room temperature for available at https://www.cambridge.org/core/terms. https://doi

Mechanisms of heat damage in proteins

“…The detection of FDNB-reactive lysine in faecal protein suggests that lysine units with free e-amino groups had passed through the digestive tract combined in indigestible peptide. Such a phenomenon would result in the measurement of FDNBreactive lysine values over-estimating the biologically available lysine ; a finding which has been reported several times in connexion with severely heated proteins (Miller, Carpenter & Milner, 1965;Ford & Salter, 1966;Boctor & Harper, 1968).…”

Availability of sulphur amino acids in protein foods

“…and Miller et al (1965) found that when methionine was determined by performic acid oxidation of the protein, followed by acid hydrolysis and chromatographic separation of methionine sulphone, results obtained with heated materials were lower than with control materials. To guard against possible artifacts resulting from the method of analysis, one laboratory determined the amino acid composition of the unoxidized protein and another laboratory carried out the determination on the protein oxidized with performic acid.…”

Nutritional value of lactose-hydrolysed milk: protein quality after some industrial processes

“…It is well documented (Donoso et al 1962;Miller, Carpenter & Milner, 1965;Pronczuk, Pawlowska & Bartnik, 1973) that changes in digestibility coefficients of heat-treated proteins are generally smaller than the reduction of the BV. Thus, absorption of unavailable amino acids or peptides containing such amino acids seems to take place to a considerable extent, and excretion of very small amounts of these compounds in the urine has been detected (Pronczuk et al 1973).…”