Effect of proteolytic modification and methionine enrichment on the nutritional value of soya albumins for rats

Protein Sources Alternative to Meat: State of the Art and Involvement of Fermentation

Meat represents an important protein source, even in developing countries, but its production is scarcely sustainable, and its excessive consumption poses health issues. An increasing number of Western consumers would replace, at least partially, meat with alternative protein sources. This review aims at: (i) depicting nutritional, functional, sensory traits, and critical issues of single-cell proteins (SCP), filamentous fungi, microalgae, vegetables (alone or mixed with milk), and insects and (ii) displaying how fermentation could improve their quality, to facilitate their use as food items/ingredients/supplements. Production of SCP (yeasts, filamentous fungi, microalgae) does not need arable land and potable water and can run continuously, also using wastes and byproducts. Some filamentous fungi are also consumed as edible mushrooms, and others are involved in the fermentation of traditional vegetable-based foods. Cereals, pseudocereals, and legumes may be combined to offer an almost complete amino acid profile. Fermentation of such vegetables, even in combination with milk-based products (e.g., tarhana), could increase nutrient concentrations, including essential amino acids, and improve sensory traits. Different insects could be used, as such or, to increase their acceptability, as ingredient of foods (e.g., pasta). However, insects as a protein source face with safety concerns, cultural constraints, and a lack of international regulatory framework.

Novel research strategy for safe use of legume proteins in human nutrition

Earlier studies on protein antinutrients and allergens naturally present in legume seeds have shown that these compounds are responsible for the impaired performance of experimental animals when exposed for a long term. These reactions were characterized by lowered nutritional performance, reduced growth, pure digestion and absorption, changes in gut motility, structural damage in small intestine and diarrhoea. A lot of efforts were made for gathering data on heat stability and resistance to chemical or enzyme treatments of these compounds to reduce or eliminate these harmful effects.A novel research approach has described that these compounds have a special regulatory role in the gut metabolism and modulate hormone and immune responses which resulted in a novel concept of “nonnutritive biologically active compound”. These studies revealed that the chemical structure of these compounds was responsible for the induction of such physiological reactions as increased endogen N-loss, change in the plasma amino acid concentration or plasma lipid composition with reduction of total cholesterol level or developing of harmful immune responses to luminal antigens resistant to the gut digestion. Resent studies were therefore related to the description of their interaction with the gut metabolism and understanding of the modulation of gut immune responses to luminal antigens.This review was inspired to summarise the research efforts on the above field performed by the Nutritional and Biological Units of the Central Food Research Institute.

Allergenicity, trypsin inhibitor activity and nutritive quality of enzymatically modified soy proteins

Two ultrafiltered soy flour protein fractions were evaluated; the first was obtained by hydrolysis (0.5-3 kDa, F(0.5-3)), and the second was an enzymatically methionine-enriched fraction (1-10 kDa, F(1-10)E). Amino acid profiles, protein quality, allergenicity (against soy-sensitive infant sera) and trypsin inhibitor activity were determined. Fraction F(1-10)E fulfilled amino acid requirements for infants, whereas the F(0.5-3) fraction was methionine deficient. Both fractions were similar in net protein utilization, and F(1-10)E digestibility was comparable with casein and higher (P?<?0.05) than F(0.5-3) or soy isolate. Allergenicity of SF was reduced to 21.5% with the hydrolysis in F(1-10)E and it was not detected in F(0.5-3.) Residual trypsin inhibitor activity with respect to soy flour was 8.1%, 3.3% and 1% for hydrolysate, F(1-10)E and F(0.5-3), respectively. Both fractions presented high nutritive quality and reduced or null allergenicity. The trypsin inhibitor activity decreased along processing and could be a useful indicator for production of hypoallergenic proteins.

Nutritional and technological evaluation of an enzymatically methionine-enriched soy protein for infant enteral formulas

Enzymatically modified soy proteins have the amino acid profile and functional properties required for dietary support. The objective of this study was to evaluate the nutritional and technological properties of an enzymatically modified soy protein ultrafiltered fraction with bound methionine (F(1-10)E) to be used as a protein ingredient for infant enteral formulas. F(1-10)E was chemically characterized and biologically evaluated. Thirty-six weaning Wistar rats were fed during 3 weeks with a 4% casein-containing diet. Rats were divided into three groups and recovered for 3 weeks with 18% protein-containing diets based on: (1) F(1-10)E, (2) casein or (3) soy isolate+methionine. Nutritional indicators were weight gain, protein efficiency ratio, plasma proteins, apparent digestibility and protein in the carcass. Additionally, F(1-10)E was added as a protein ingredient of an enteral formula, and its sensory and rheological properties were compared with a hydrolyzed-whey protein commercial formula. F(1-10)E contained 68% protein and 5% sulphur amino acids, with 60% of peptides </=6 kDa. Casein-based and F(1-10)E-based diets were comparable (P>0.05) in weight gain (108 g and 118 g, respectively), protein efficiency ratio (2.7), apparent digestibility (93% and 95%), plasma proteins (5.7 mg/100 ml) and carcass protein (61%), and better than soy isolate-based+methionine diet (P<0.05). Viscosity of the commercial formula and our formula was similar during a 24-h period. Sensory acceptability was 8 for our formula and 3.5 for the commercial one, on a scale of 1-10 (P<0.05). Due to its nutritional, sensorial and rheological properties, F(1-10)E could be used as a protein source in infant enteral formulas.

Nutritional and clinical evaluation of a modified soy protein with covalently bound branched-chain amino acids in cirrhotic sprague-dawley rats

Several studies suggested that branched-chain amino acids (BCAA) improve plasma amino acid imbalance as well as protein metabolism in patients with cirrhosis. However, commercial formulas supplemented with free BCAA have their limitations. We evaluated a modified soy protein diet with covalently bound BCAA (diet M) by comparing it with diets based on casein (diet C) or Hepatic Aid II (diet H; commercial formula) as protein sources. After 3 weeks of bile duct obstruction, 24 Sprague-Dawley rats divided into three groups received diets with 9% (w/w) protein/amino acids for 7 days. Nutritional and clinical parameters were determined. Nitrogen balance and weight gain (g)/protein intake (g) with diet M (0.19 +/- 0.31 and 1.33 +/- 1.43 g, respectively) were significantly higher (p < 0.05) than with diet H (-0.34 +/- 0.20 and -0.34 +/- 1.11 g), but comparable to those with diet C (0.04 +/- 0.38 and 0.20 +/- 0.93 g). Animals on diet M had a significantly (p < 0.05) increased plasma BCAA:aromatic amino acid ratio (1.8 +/- 0.3) as compared with those on diets H (1.3 +/- 0.1) and C (0.8 +/- 0.0). There were no significant differences in organ weight or liver function among the groups. We conclude that the BCAA-modified protein is an attractive option in the nutritional support of patients having cirrhosis.

Metal ions restore the proteolytic resistance of denatured conglutin gamma, a lupin seed glycoprotein, by promoting its refolding

The susceptibility to trypsin of conglutin gamma, a lupin seed glycoprotein affected by this enzyme only when in a non-native conformation, was used to study the effect of Zn(2+) and other metal ions on the structural dynamics of the protein. When acid-treated trypsin-susceptible conglutin gamma was incubated at neutral pH in the presence of Zn(2+), it became resistant to tryptic attack, contrary to the protein treated in the absence of Zn(2+). The time course of this refolding event has been quantitatively evaluated by SDS-PAGE. Amino acid sequencing of the major polypeptide fragments, produced by trypsin before completion of the refolding process, indicated that only a few cleavable bonds were accessible to the enzyme. This suggested that the presence of metal ions affected the pathway of degradation of the protein, by inducing its folding. Among the other metal ions tested, Ni(2+) also promoted the adoption of a trypsin-resistant conformation of conglutin gamma, whereas Mn(2+) and Ca(2+) had only much lower effects. The relevance of these findings for a deeper understanding of the in vivo degradation of plant food proteins and how it is affected by metal ions are discussed.