Proteins from land plants – Potential resources for human nutrition and food security

The bioavailability of iron, zinc, protein and vitamin A is highly variable in French individual diets: Impact on nutrient inadequacy assessment and relation with the animal-to-plant ratio of diets

Nutritional adequacy depends on nutrient intakes and bioavailability which strongly varies with the plant- or animal-origin of foods. The aim was to estimate iron, zinc, protein and vitamin A bioavailability from individual diets, and investigate its relation with the animal-to-plant ratio (A/P) of diets. Bioavailability was estimated in 1899 French diets using diet-based algorithms or food-group specific conversion factors. Nutrient inadequacy was estimated based on i) bioavailability calculated in each individual diet and ii) average bioavailability assumed for Western-diets. Mean iron absorption, zinc absorption, protein quality and β-carotene conversion factor were 13%, 30%, 92%, and 17:1, respectively. Bioavailability displayed a high variability between individual diets, poorly explained by their A/P. Using individual bioavailability led to different inadequacy prevalence than with average factors assumed for Western-diets. In this population, the A/P does not seem sufficient to predict nutrient bioavailability and the corresponding recommended intakes. Nutritional adequacy should be assessed using bioavailability accounting for individual diets composition.

Food and nutritional security requires adequate protein as well as energy, delivered from whole-year crop production

Human food security requires the production of sufficient quantities of both high-quality protein and dietary energy. In a series of case-studies from New Zealand, we show that while production of food ingredients from crops on arable land can meet human dietary energy requirements effectively, requirements for high-quality protein are met more efficiently by animal production from such land. We present a model that can be used to assess dietary energy and quality-corrected protein production from various crop and crop/animal production systems, and demonstrate its utility. We extend our analysis with an accompanying economic analysis of commercially-available, pre-prepared or simply-cooked foods that can be produced from our case-study crop and animal products. We calculate the per-person, per-day cost of both quality-corrected protein and dietary energy as provided in the processed foods. We conclude that mixed dairy/cropping systems provide the greatest quantity of high-quality protein per unit price to the consumer, have the highest food energy production and can support the dietary requirements of the highest number of people, when assessed as all-year-round production systems. Global food and nutritional security will largely be an outcome of national or regional agroeconomies addressing their own food needs. We hope that our model will be used for similar analyses of food production systems in other countries, agroecological zones and economies.

Proteomic analysis of mature barley grains from C-hordein antisense lines

Hordeins are the major storage proteins in barley grains and are responsible for their low nutritional quality. Previously, antisense C-hordein barley lines were generated and were shown to contain a more balanced amino acid composition and an altered storage protein profile. In the present study, a proteomic approach that combined two-dimensional gel electrophoresis (2-DE) and mass spectrometry was used to (1) identify the changes in the protein profile of non-storage proteins (salt soluble fraction) in antisense C-hordein barley lines (L1, L2 and L3) and (2) map the differentially expressed proteins compared to the non-transgenic control line (Hordeum vulgare cv. Golden Promise). Moreover, the changes in the proteins were correlated with the more balanced amino acid composition of these lines, with special attention to the lysine content. The results showed that suppression of C-hordein expression does not exclusively affect hordein synthesis and accumulation. The more balanced amino acid composition observed in the transgenic lines L1, L2 and L3 was an indirect result of the profound alterations in the patterns of the non-storage proteins. The observed changes included up-regulated expression of the proteins involved in stress and detoxification (L1), defence (L2 and L3), and storage globulins (L1, L2 and L3). To a lesser extent, the proteins involved in grain metabolism were also changed. Thus, the increased essential amino acids content results from changes in distinct protein sources among the three antisense C-hordein lines analyzed, although the up-regulated expression of lysine-rich proteins was consistently observed in all lines.

Relevance of the Functional Properties of Enzymatic Plant Protein Hydrolysates in Food Systems

Proteins play a crucial role in determining texture and structure of many food products. Although some animal proteins (such as egg white) have excellent functional and organoleptic properties, unfortunately, they entail a higher production cost and environmental impact than plant proteins. It is rather unfortunate that plant protein functionality is often insufficient because of low solubility in aqueous media. Enzymatic hydrolysis strongly increases solubility of proteins and alters their functional properties. The latter is attributed to 3 major structural changes: a decrease in average molecular mass, a higher availability of hydrophobic regions, and the liberation of ionizable groups. We here review current knowledge on solubility, water- and fat-holding capacity, gelation, foaming, and emulsifying properties of plant protein hydrolysates and discuss how these properties are affected by controlled enzymatic hydrolysis. In many cases, research in this field has been limited to fairly simple set-ups where functionality has been assessed in model systems. To evolve toward a more widely applied industrial use of plant protein hydrolysates, a more thorough understanding of functional properties is required. The structure-function relationship of protein hydrolysates needs to be studied in depth. Finally, test model systems closer to real food processing conditions, and thus to real foods, would be helpful to evaluate whether plant protein hydrolysates could be a viable alternative for other functional protein sources.

Intake of Meat Proteins Substantially Increased the Relative Abundance of Genus Lactobacillus in Rat Feces

Diet has been shown to have a critical influence on gut bacteria and host health, and high levels of red meat in diet have been shown to increase colonic DNA damage and thus be harmful to gut health. However, previous studies focused more on the effects of meat than of meat proteins. In order to investigate whether intake of meat proteins affects the composition and metabolic activities of gut microbiota, feces were collected from growing rats that were fed with either meat proteins (from beef, pork or fish) or non-meat proteins (casein or soy) for 14 days. The resulting composition of gut microbiota was profiled by sequencing the V4-V5 region of the 16S ribosomal RNA genes and the short chain fatty acids (SCFAs) were analyzed using gas chromatography. The composition of gut microbiota and SCFA levels were significantly different between the five diet groups. At a recommended dose of 20% protein in the diet, meat protein-fed rats had a higher relative abundance of the beneficial genus Lactobacillus, but lower levels of SCFAs and SCFA-producing bacteria including Fusobacterium, Bacteroides and Prevotella, compared with the soy protein-fed group. Further work is needed on the regulatory pathways linking dietary protein intake to gut microbiota.

Modifying the Cold Gelation Properties of Quinoa Protein Isolate: Influence of Heat-Denaturation pH in the Alkaline Range

Heat-denaturation of quinoa protein isolate (QPI) at alkali pH and its influence on the physicochemical and cold gelation properties was investigated. Heating QPI at pH 8.5 led to increased surface hydrophobicity and decreases in free and bound sulfhydryl group contents. Heating at pH 10.5 caused a lesser degree of changes in sulfhydryl groups and surface hydrophobicity, and the resulting solutions showed drastically increased solubility. SDS PAGE revealed the presence of large aggregates only in the sample heated at pH 8.5, suggesting that any aggregates present in the sample heated at pH 10.5 were non-covalently bound and disintegrated in the presence of SDS. Reducing conditions partially dissolved the aggregates in the pH 8.5 heated sample indicating the occurrence of disulphide bonding, but caused no major alterations in the separation pattern of the pH 10.5 heated sample. Denaturation pH influenced the cold gelation properties greatly. Solutions heated at pH 8.5 formed a coarse coagulum with maximum G' of 5 Pa. Heat-denaturation at 10.5 enabled the proteins to form a finer and regularly structured gel with a maximum G' of 1140 Pa. Particle size analysis showed that the pH 10.5 heated sample contained a higher level of very small particles (0.1-2 μm), and these readily aggregated into large particles (30-200 μm) when pH was lowered to 5.5. Differences in the nature of aggregates formed during heating may explain the large variation in gelation properties.

The effect of deamidation on the structural, functional, and rheological properties of glutelin prepared from Akebia trifoliata var. australis seed

The characteristics of glutelin samples from Akebia trifoliata var. australis seeds (AG) that had been deamidated by malic acid (MDAG) and by citric acid (CDAG) were investigated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed high-molecular-weight subunits that were degraded into smaller fragments, and FTIR indicated a decrease in the number of β-sheet groups and an increase in the amount of β-turns in the deamidated samples. These results could be caused by the cleaving of partial disulfide bonds to form new sulfhydryl groups during deamidation. Citric acid was found to be more effective at deamidation and hydrolysis, resulting in a higher solubility and emulsifying activity for CDAG, and MDAG also exhibited some improvement in terms of surface hydrophobicity and emulsion ability. Rheology showed that the gelation point for deamidated samples was increased, and the gel network was strengthened. The amounts of essential amino acids that were well-preserved and the improved solubility, emulsification, and rheology properties of AG after acid-heating deamidation show that this technique can be useful for treating other plant-based food ingredients in the future.

Characterization of heat-set gels from RuBisCO in comparison to those from other proteins

To anticipate a future shortage in functional proteins, it is important to study the functionality of new alternative protein sources. Native RuBisCO was extracted from spinach, and its gelation behavior was compared to other native proteins from animal and plant origins. Protein gels were analyzed for their mechanical gel properties during small and large deformation and for their microstructure. Heat-induced aggregation and network formation of RuBisCO resulted in gels with unique characteristics compared to, for example, whey protein and egg white protein. Having a very low critical gelling concentration and low denaturation temperature, RuBisCO readily forms a network with a very high gel strength (G', fracture stress), but upon deformation it has a brittle character (low critical strain, low fracture strain). This breakdown behavior can be explained by the dominant role of hydrophobic and hydrogen bonds between RuBisCO molecules during network formation and by the coarse microstructure. RuBisCO was shown to exhibit high potential as a functional ingredient giving opportunities for the design of new textures at low protein concentration.

Chemical Characterization and Nutritional Analysis of Protein Isolates from Caragana korshinskii Kom

Plant-based proteins are valuable supplements to compensate the gap between supply and demand in the food or feed industry. However, they lack essential amino acids, such as lysine in cereal grains and sulfur-containing amino acids in legumes, which greatly limit their wider uses for human and animals. In this study, the contents of nutritional ingredients and antinutritional factors of Caragana korshinskii Kom. and its protein isolates were quantitatively investigated. It was shown that the crude protein contents of C. korshinskii Kom. and its protein isolates obtained by alkaline extraction method (Al-CPI) and acetone precipitation method (A-CPI) were 9.1, 50.1, and 42.6%, respectively. Amino acid contents in C. korshinskii Kom., Al-CPI, and A-CPI basically exceeded the FAO/WHO (2007) reference pattern for adults except sulfur-containing amino acids. The lysine levels in C. korshinskii Kom., Al-CPI, and A-CPI were 4.1, 3.1, and 3.8 mg/100 mg crude protein respectively, which were higher than some other kinds of cereal grains. The methionine in A-CPI (1.39 mg/100 mg crude protein) was even higher than that in soybean. The antinutritional factors in C. korshinskii Kom. and Al-CPI were generally lower than those in some other kinds of legumes except total phenol and tannin. Total phenol and tannins in Al-CPI were 19.02 and 5.66 mg/g dry substance, respectively, but they were undetectable in A-CPI. This study provided a detailed analysis on nutritional and antinutritional factors in C. korshinskii Kom. and its protein isolates, indicating that they have a great potential on food and feed additives.

Seaweeds as potential therapeutic interventions for the metabolic syndrome

Seaweeds are a characteristic part of the traditional diet in countries such as Japan and Korea; these countries also have a lower prevalence of metabolic syndrome than countries such as the USA and Australia. This suggests that seaweeds may contain compounds that reduce the characteristic signs of obesity, diabetes, hypertension, fatty liver and inflammation in the metabolic syndrome. Potentially bioactive compounds from seaweeds include polysaccharides, peptides, pigments, minerals and omega-3 fatty acids. This review emphasises current research on these compounds in isolated cells, animal models and patients. Key problems for future research include chemical characterisation of the bioactive principles, defining pharmacological responses in all aspects of the metabolic syndrome, determining if a therapeutic dose has been administered, and defining oral bioavailability of the active ingredients.