Actual problems of research in food science.

Starting from the necessary trend towards development in the field of food production, the author outlines, on the basis of current knowledge, the problems to be solved in food science. A general research conception is deduced for the essential nutrient "protein" (as an example) which is illustrated by results from studies on protein fibre and protein gel formation.

On the viscosity behaviour of field bean protein isolates in dependence on their degree of acetylation.

The increase of apparent viscosity when protein concentration is raised becomes more and more distinctly pronounced with an increasing degree of acetylation and is displaced at lower protein concentrations. Investigations of the influence of temperature on viscosity behaviour are therefore carried out on the basis of comparable initial viscosity. 20 min heat treatment at different temperatures shows that above 40 degrees C the order of magnitude of the temperature-induced increase in viscosity depends decisively on the degree of acetylation. With an increasing degree of acetylation there is a comparably stronger increase in viscosity. An increase of viscosity is also linked to increasing duration of the heat treatment. The higher the degree of acetylation, the greater--related to a defined duration of heat treatment--is the growth of viscosity. During the heating phase in cyclical temperature tests a viscosity maximum is formed at 60 degrees C, which becomes more and more distinctly pronounced with an increasing degree of acetylation. From computerised evaluation of flow curves it is generally established that the complexity of flow properties increases with increasing degree of acetylation, increasing concentration of protein and the effect of heat.

[Swelling properties and structural stability of spun protein fibers]. / Untersuchungen zum Quellungsvermögen und zur Strukturstabilität von Proteinfasern

With spun protein fibers of casein and a mixture of casein and vegetable proteins results in a solution of sodium hydrogencarbonate an increased diameter of the protein fibers. The determination of this change makes possible an examination of the swellability and stability of the structure of protein fibers.

[Effect of starchsulfate on properties of protein fibers]. / Der Einfluss von Stäkesulfat auf die Eigenschaften von Proteinfasern

Admixture of starchsulphate to an alkaline spinning solution of proteins increases the thermostability of the corresponding spun protein fibers.

[Nutritional study of field bean protein isolate and of spun field bean protein-casein fibers]. / Ernährungsphysiologische Untersuchungen an Ackerbohnenproteinisolat und Ackerbohnenprotein-Casein-Fasern

The amino acid composition of the different field bean protein isolates shows a good correspondence. In relation to casein the content of the whole essential amino acids is low. In the first line the low content of methionine and cystine limits the biological value of this proteins. The content of lysine is relatively high. The enzymatic in vitro-hydrolysis results in a corresponding availability of the amino acids between the field bean proteins and casein. The digestibility is very good, the biological value with less than 50 relatively low. Apart from the low content of the sulphur containing amino acids the amino acid composition of the spun field bean protein/casein(I:I) fibers corresponds with the calculated value; the enzymatic availability of the fibers is also comparable with casein. The digestibility in the nitrogen balance test is very good and the biological value of the fiber corresponds with that of casein.

[Nutritional-physiological studies on acetylated fractions of protein from Vicia faba]. / Ernährungsphysiologische Untersuchungen an acetylierten Vicia-faba-Proteinfraktionen.

The nutritional-physiological value of an easily soluble and of a difficulty soluble fraction of protein from Vicia faba (showing a degree of acetylation of 0%, 43% and 94%, respectively) was characterized by determining the amino-acid content, the enzymatic amino-acid availability and the nitrogen balance in the rat. The results from both the amino-acid analysis and the animal experiments on the biological value evidenced that the nutritional-physiological value of the easily soluble fraction of protein from Vicia faba is significantly lower, which is in particular attributable to its lower content of sulphur-containing amino acids. Acetylation did not reduce the nutritional-physiological value of the easily soluble fraction of protein from Vicia faba, and impaired that of the difficulty soluble fraction but slightly. From the viewpoint of nutritional physiology, there are no objections against the use of these protein fractions as food additives.

Effect of spinning and additional cross-linking with dialdehyde starch or aluminum ions on the digestibility and quality of casein-Vicia faba protein isolate mixtures.

Studies were made in adult rats using an isotopic 15N method. Whole egg, wheat, casein and Vicia faba protein isolate served as reference proteins. The diets were isonitrogenous and feed intake was adjusted to the maintenance energy level. Variations in true N digestibility were small (91.8-96.1%). The amount of metabolic fecal nitrogen in animals receiving the diet containing wheat was 9.4 mg/100 g body weight compared with 4.9-5.8 mg in the other diets. The differences in nutritional quality for maintenance between proteins of plant and animal origin were small. However, spinning (alkaline treatment) and additional cross-linking with aluminum ions or dialdehyde starch affected the nutritional quality for maintenance.

[Nutritive-physiological study of sunflower seed protein isolate and spun sunflower seed protein-casein fibers]. / Ernährungsphysiologische Untersuchungen an Sonnenblumensaatproteinisolat und Sonnenblumensaatprotein-Casein-Fasern

Compared with defatted sunflower seeds, in sunflower seed globulin isolates the content of lysine and sulphur containing amino acids is decreased, the content of phenylalanine is increased. The content of the whole essential amino acids of sunflower seed globulin isolate in relation to casein is decreased. The value of the enzymatic invitro available amino acids of sunflower seed globulin is comparable with casein. The digestibility is good, the biological value is in relation to defatted sunflower seed lower. Apart from the lower content of sulphur-containing amino acids the amino acid composition of spun sunflower seed globulin/casein (I:I) fibers corresponds with the calculated value; in relation to sunflower seed globulin isolate the content of lysine and the whole essential amino acids of the spun protein fibers is increased. The enzymatic in-vitro-hydrolysis results altogether in a comparable availability of the amino acids between spun protein fibers and sunflower seed globulin isolates. The digestibility and the biological value of spun protein fibers corresponds with that of casein.

Digestibility and dietary quality of nonacetylated and acetylated Vicia faba proteins in maintenance. Studies on 15N-labelled adult rats.

N digestibility and the dietary quality of a Vicia faba protein isolate as well as of two protein fractions from this isolate, acetylated and nonacetylated, were estimated in 15N-labelled adult rats. For reference, whole egg, casein and wheat were studied. The diets were fed at maintenance energy intake level. Daily metabolic fecal nitrogen estimated by an isotopic method was 5 mg/100 g body weight in animals receiving whole egg, casein, or Vicia faba proteins. When wheat was included in the diet metabolic fecal nitrogen was increased to 140% of this value. True N digestibility of reference proteins was 91-92% and of Vicia faba proteins 95-97%. Protein quality for maintenance was high and similar for all proteins. Acetylation affected neither N digestibility nor protein quality under maintenance conditions.

[Spinning of rapeseed proteins]. / Untersuchungen zur Verspinnung von Rapssaatproteinen

Alkaline solutions of a mixture from rapeseed globulin and casein show plastic flow, which is influenced by protein concentration, relation of rapeseed globulin and casein, temperature and time of storage of the protein solution. The sodium hydroxide concentration with a great variability doesn't take effect on the rheological properties. With increasing content of casein in such alkaline solutions of rapeseed globuline and casein results an approach to NEWTONian flow. The spinnability of alkaline solutions of a mixture from rapeseed globulin and casein and the properties of the corresponding spun protein fibers are influenced by protein concentration, relation of rapeseed globulin and casein of the spinning solution and temperature of coagulating bath. The sodium hydroxide content of the spinning solution and the hydrochloric acid concentration of the coagulating bath with a great variability don't take effect. The spinnability of alkaline solutions of a mixture from rapeseed albumin starchsulphate and casein and the properties of the corresponding spun protein fibers compared to rapeseed globulin-casein mixtures are influenced additionally by sodium hydroxide concentration of the spinning solution and hydrochloric acid content of coagulating bath. The favourable influence on the properties of spun rapeseed albuminstarchsulphate-casein fibers isn't increased by a growth of the rapeseed albumin starchsulphate content more then 4% of the protein concentration of the spinning solution.

[Changes in the nutritive physiological value of proteins modified by dialdehyde starch]. / Die Beeinflussung des ernährungsphysiologischen Wertes von mit Dialdehydstärke modifizierten Proteinen

The reaction of dialdehyde starch with the proteins of certain model protein texturates produces changes in the nutrition physiological quality of the proteins. Under the experimental conditions chosen, these changes were barely or not at all detectable by amino-acid analysis. On using the technique of aminoacid liberation under in vitro conditions, these changes were evidenced only for lysine and arginine. The determination of the lysine availability, however, testifies to a reversible or irreversible change of lysine which reduces significantly the PER values (animal experiments) of protein texturates treated with 100% oxidized dialdehyde starch. The differences between the NPU values were but insignificant. In spite of the detectable change in protein quality, the quality of the model protein texturates tested still satisfies the criteria for proteins with a composition which is favourable from the viewpoint of nutrition physiology.

[Amino acid composition of the unresorbed peptide fractions of the distal part of the small intestine in rats. II. Feeding of field-bean protein isolate with and without the addition of dialdehyde starch and of protein texturates from it]. / Untersuchungen über die Aminosäurezusammensetzung von nichtresorbierten Peptidfraktionen des distalen Dünndarminhaltes von Ratten. 2. Mitt. Verfütterung von Ackerbohnenproteinisolat mit und ohne Dialdehydstärkezusatz und von daraus hergestellten Proteintexturaten.

Rats were fed diets containing 20% protein in the form of casein, protein isolate from sunflower seeds, protein isolate from field beans, model protein texturate made from field-bean protein isolate or model protein texturate made from field-bean protein isolate treated with dialdehyde starch and a nitrogenfree diet. The content in the distal small intestine of the rats was collected 3 hours after feeding, and the amino-acid compositions of the TCA-precipitable and TCA-soluble peptides (after separation of free amino acids) of the content were studied. The comparison of the amino-acid compositions of the two peptide fractions with the respective dietary protein showed no agreement. On the contrary, the comparison of the amino-acid compositions of the two peptide fractions determined after protein-free diet with those found after protein ingestion were in good agreement, independently of the kind of dietary protein. The comparison of the two peptide fractions with one another revealed an increased degree of proteolytic decomposition of the TCA-soluble peptides. As compared to the other protein-containing diets and to the protein-free diet, diets containing field-bean protein caused an increase of TCA-precipitable peptides and an increase of glycine in both fractions. This was also observed in model protein texturates containing only 30% field-bean protein. Treatment with dialdehyde starch produces certain alterations of the basic amino acids and their accumulation in the fractions of undigested peptide.

[Amino acid composition of unresorbed peptide fractions in the contents of the distal part of rat small intestine. 1. Nitrogen-free diet and diets with casein, sunflower protein isolate and defatted sunflower seeds]. / Untersuchungen über die Aminosäurezusammensetzung von nichtresorbierten Peptidfraktionen des distalen Dündarminhaltes von Ratten. 1. Mitt. N-freie Versuchsdiät und Versuchsdiäten mit Casein, Protein-isolat aus Sonnenblumensaat und entfetteter Sonnenblumensaat

After feeding with protein containing diets the protein quantity increases in the aqueous supernatant (U1), in the trichloracetic acid soluble (U2) and precipitable (S2) fractions of the content of the distal part of the small intestine of rats. Independent of the dietary proteins the amino acid composition of both fractions (S2 and the peptides from U2) is similar in relation to protein-free feeding; a similarity with the amino acid composition of the dietary proteins doesn't exist. In relation to fraction S2 the peptides of fraction U2 show anording to the higher content of amino acids, which are difficult to liberate by protein cleavage, a high proteolytic degradation.

[Physiological nutrition studies of swine for the evaluation of modified proteins. 3. Relationship between the true and apparent N digestibility and amino acid absorption of the small intestines and the parameters of N metabolism]. / Ernährungsphysiologische Untersuchungen an Schweinen zur Beurteilung von modifizierten Proteinen. 3. Mitteilung. Zusammenhänge zwischen wahrer und scheinbarer N-Verdaulichkeit bzw. Aminosäurenresorption bis zum Ende des Dünndarmes und Parametern des N-Umsatzes.

Modified proteins were tested in absorption investigations with eight pigs with ileocaecal re-entrant cannulae. The apparent digestibility up to the end of the small intestines showed considerable differences between the feed proteins (77-93%). The same differences could be observed with regard to the apparent absorption of amino acids. Concerning the true N-digestibility resp. the true absorption of the amino acids in the above mentioned section of the intestinal tract there were hardly any differences between the proteins given. The results show that there is a relation between the amount of endogenous N in the chyme at the end of the small intestines and the protein consumed. The amount of endogenous N in the chyme in the small intestines influence N-excretion in urine and thus the intermediary utilisation of feed protein. From the point of view of nutrition physiology it follows that the spun vicia-faba protein/casein (1 : 1) fibres (C) approximate best the value of casein (A). While the treatment of this mixed protein with dyaldehyde starch had a negligible effect on the ascertained parameters only, the treatment of the same protein with aluminium chloride diminished its value more. The isolated vicia-faba (B) was the poorest of the modified proteins tested.

[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]. / Ernährungsphysiologische Untersuchungen an Schweinen zur Beurteilung von modifizierten Proteinen. 1. Mitteilung. Ergebnisse der N-Umsatzmessung, scheinbare und wahre Proteinverdaulichkeit sowie scheinbare und wahre Aminosäureresorption bis zum Ende des Verdauungstraktes.

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.

[Nutritional and physiological studies of swine for the evaluation of modified proteins. 2. Determination of endogenous N in the contents of the small intestines using the 15N-tracer method]. / Ernährungsphysiologische Untersuchungen an Schweinen zur Beurteilung von modifizierten Proteinen. 2. Mitteilung. Bestimmung des endogenen N im Dünndarminhalt mit Hilfe der 15N-Tracertechnik.

The endogenous N-quota in the chyme of the small intestines after providing modified proteins was determined with re-entrant cannulae at the end of the ileum in investigations with pigs (35 to 50 kg live weight) with the isotope dilution method. The N-pool of the test animals was labelled with 15N-glycine and 15N-leucine. The TCA-soluble fraction of the blood plasma served as criterion for the labelling level of the N-pool. The results showed a direct connection between N-intake and endogenous N in the chyme of the small intestines. With regard to N-intake, the dependence of endogenous N in the chyme of the small intestines on feed protein could be observed.

Production, characterization and application of protein isolates from shark. Part 3. Characterization of protein isolates.

The functional and nutritional characterization of two isolates elaborated through cleaning-extraction processes, as well as that of a third isolate obtained by means of a chemical modification (alkaline heat treatment) from one of the former, was carried out. The first two isolates exhibit in general similar properties, are nutritionally comparable with casein and show a fairly high water absorption, having a potentially great value for instance in bakery and meat products and pastes. The modified isolate is essentially different from the isolate used as raw material in many of the characterized parameters, having a high nitrogen solubility index (NSI) by pH 3.5 and 7.0 and thus offering its possible use in such food systems as soft drinks where a high solubility is desired.

[Rheology and spinning of alkaline solution of field bean protein and casein]. / Zur Rheologie und Verspinnung alkalischer Lösungen aus Ackerbohnenprotein und Casein

From field bean protein and a mixture of field bean protein with casein to equal parts are prepared with sodium hydroxide high protein-containing alkaline solutions, which show pseudoplastic flow. The flow curves of the pseudoplastic field bean protein-casein (I:I)-solutions are described mathematically with the Ostwaldian power statement. In a suitable scope of spinning of this solutions are carried out complete factorial experiments, which guide to regression equations of lg k and n. g k depends on the concentration of protein; an effect of the sodium hydroxide concentration exists lonly about interactions. On the other hand the flow exponent n depends on the hydroxide concentration. The properties of the spun field bean protein/casein (I:I) fibres are described.

[Characterization and spinning of alkaline solutions of wheat protein and casein]. / Zur Charakterisierung und Verspinnung alkalischer Lösungen aus Weizenprotein und Casein

The viscosity behaviour of alkaline solutions of mixtures from different wheat glutens with casein in dependence on the concentration of the whole protein, wheat protein, sodium hydroxide, sodium chloride and on the temperature, time and the effect of treatment of wet wheat gluten with sodium chloride or sodium hydroxide on the properties of the spun wheat protein/casein fibers are described. Based on this model experiments the rheological behaviour of alkaline solutions of wheat protein/casein (I:2) and proceed from the parameters of the spinning process the properties of the corresponding spun fibers are represented.