A practical reference on Size-exclusion chromatography: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-02-04 and is reviewed periodically as new material appears.
Quality control for whey protein hydrolysate combines compositional and molecular tests. Protein content is measured by Kjeldahl or Dumas nitrogen determination. Moisture, ash, fat, and lactose are checked with standard food methods. The degree of hydrolysis is estimated by TNBS, OPA, or pH-stat procedures that quantify free amino groups or released protons. Molecular weight distribution is examined by size-exclusion chromatography or SDS-PAGE. These tests describe average peptide size rather than exact peptide sequences, and results depend on standards and calibration.
Advanced peptide profiling uses liquid chromatography coupled with mass spectrometry to identify fragments and assess batch consistency. Amino acid analysis after acid hydrolysis quantifies the building blocks and can reveal deviations from expected composition. Residual enzyme activity may be monitored in products where active enzymes are undesirable. Allergen tests often use immunoassays for beta-lactoglobulin, but hydrolysis can reduce or alter epitope recognition, so negative results do not prove absence of allergenic potential. Physical tests include particle size, bulk density, and reconstitution behavior.
Regulatory and labeling frameworks vary by country. In the United States, whey protein hydrolysate may be regulated as a food ingredient or a dietary supplement ingredient depending on intended use. In the European Union, it falls under general food law, with additional rules for infant formula and foods for special medical purposes. A claim of hypoallergenicity is not established by hydrolysis alone and generally requires clinical evidence. Open questions remain about how degree of hydrolysis relates to bitterness, nitrogen absorption, and residual allergenicity across different products and processing methods.
Whey protein hydrolysate is a dairy ingredient made by treating whey protein with proteases that cleave peptide bonds. The starting material is typically whey protein concentrate or isolate, which contains beta-lactoglobulin, alpha-lactalbumin, and smaller amounts of bovine serum albumin and immunoglobulins. Hydrolysis shortens protein chains into peptides and free amino acids, changing solubility, viscosity, and flavor compared with intact whey protein. The extent of cleavage is commonly described by degree of hydrolysis, a percentage of broken peptide bonds relative to total bonds.
Enzyme choice influences the peptide size distribution and the resulting functional properties. Some proteases cut at specific amino acid residues, while others act more broadly, so two hydrolysates with the same degree of hydrolysis can differ in peptide sequences. Short peptides are generally more water-soluble and less likely to form gels under heat, although bitterness can increase when hydrophobic residues become exposed. The relationship between peptide length, taste, and bioactivity is an active area of study, and not all proposed effects are established in human trials.
| Property | Value | Notes |
|---|---|---|
| Protein determination | Kjeldahl nitrogen × 6.38 | Dumas combustion also used |
| Degree of hydrolysis | TNBS, OPA, or pH-stat | Results method-dependent |
| Molecular weight distribution | SEC-HPLC or SDS-PAGE | Reports ranges, not sequences |
| Residual lactose | Enzymatic or HPLC | Relevant for low-lactose products |
| Microbiological limit | Total plate count < 10^4 CFU/g | Typical internal specification, varies |
Routine quality control for hydrolysate powders includes total nitrogen or protein content by Kjeldahl or Dumas combustion, moisture by oven or Karl Fischer titration, ash, and mineral profiles. Microbiological tests typically cover total aerobic counts, yeasts, molds, and specified pathogens according to regional food safety rules. Amino acid analysis can quantify free amino acids and peptide-bound residues after hydrolysis. For products intended for special populations, additional tests may target residual lactose, fat, or specific allergenic proteins. Specifications are set by the manufacturer and may exceed general food-grade requirements.
Hydrolysate powders are hygroscopic and can absorb moisture during storage, which may promote caking, browning, and loss of solubility. Cool, dry conditions and sealed packaging slow these changes, while high humidity and warm temperatures accelerate Maillard reactions between peptides and residual sugars. Liquid hydrolysates are more perishable and often require refrigeration or preservatives. Shelf-life studies usually monitor moisture, color, solubility, free amino groups, and microbial load over time. Stability depends on residual lactose, water activity, packaging barrier properties, and the initial peptide profile.
Whey protein hydrolysate appears in infant formula, sports nutrition, and clinical nutrition. In infant formula, extensively hydrolyzed products are used when a reduced allergenicity is desired, though not all hydrolysates are hypoallergenic. In sports products, the ingredient is marketed for rapid amino acid delivery, but the practical advantage over intact whey protein remains debated. Research often compares hydrolysate with isolate or concentrate for absorption kinetics, muscle protein synthesis, and gastrointestinal tolerance. Regulatory categories differ by country, and label terms such as partially hydrolyzed or extensively hydrolyzed are defined in some jurisdictions but not others.
Whey protein hydrolysate is a dairy ingredient made by treating whey protein with proteolytic enzymes. The starting material is whey, the liquid remaining after cheese or casein production, and its main proteins include beta-lactoglobulin, alpha-lactalbumin, and bovine serum albumin. Enzyme action breaks peptide bonds, producing shorter peptides and some free amino acids. The result is not a single uniform substance; composition depends on whey source, enzyme type, hydrolysis conditions, and downstream filtration. Hydrolysates are often described by average peptide length or degree of hydrolysis rather than by one fixed molecular weight.
Compared with whey protein concentrate or isolate, hydrolysate has a smaller average peptide size and a higher proportion of low-molecular-weight fractions. This change can affect solubility, viscosity, osmolality, taste, and foam formation. Some hydrolysates are bitter because hydrophobic peptides are exposed during cleavage. The term hydrolysate does not indicate a guaranteed peptide profile; two products with the same reported hydrolysis value can differ in peptide sequence and residual intact protein. Commercial specifications usually state protein content, moisture, ash, fat, and microbiology, while peptide distribution may be reported as a range.
Stability and storage practices affect measured quality over time. Hydrolysate powders are hygroscopic and can absorb moisture, leading to caking, Maillard browning, and reduced solubility. Cool, dry storage in sealed containers limits these changes, while high humidity and warm temperatures accelerate them. Microbiological testing for total aerobic counts, yeasts, molds, and specified pathogens is typical for food ingredients. Regulatory status varies by country; in many jurisdictions hydrolyzed whey protein is regulated as a food ingredient rather than a drug, and claims about reduced allergenicity require specific substantiation.
Quality control for whey protein hydrolysate begins with verifying protein content, moisture, ash, and fat using standard food analysis methods. Total nitrogen by Kjeldahl or Dumas combustion gives an estimate of protein, often calculated with a dairy-specific conversion factor. Amino acid analysis after acid hydrolysis quantifies individual residues but destroys tryptophan and may convert glutamine and asparagine. The extent of peptide bond cleavage is usually estimated by measuring free amino groups, soluble nitrogen, or trichloroacetic acid-soluble peptides. These tests are operationally defined and can give different results across laboratories.
Microscopically, each liver lobe is seen to be made up of hepatic lobules. The lobules are roughly hexagonal, and consist of plates of hepatocytes, and sinusoids radiating from a central vein towards an imaginary perimeter of interlobular portal triads. The central vein joins to the hepatic vein to carry blood out from the liver. A distinctive component of a lobule is the portal triad, which can be found running along each of the lobule's corners. The portal triad consists of the hepatic artery, the portal vein, and the common bile duct. The triad may be seen on a liver ultrasound, as a Mickey Mouse sign with the portal vein as the head, and the hepatic artery, and the common bile duct as the ears. Histology, the study of microscopic anatomy, shows two major types of liver cells: parenchymal cells and nonparenchymal cells. About 70–85% of the liver volume is occupied by parenchymal hepatocytes. Nonparenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume. The liver sinusoids are lined with two types of cell, sinusoidal endothelial cells, and phagocytic Kupffer cells. Hepatic stellate cells are nonparenchymal cells found in the perisinusoidal space, between a sinusoid and a hepatocyte. Additionally, intrahepatic lymphocytes are often present in the sinusoidal lumen.
hydrogenation Any chemical reaction between molecular hydrogen (H2) and another chemical species, typically resulting in the reduction or saturation of the other species by the addition of one or more pairs of hydrogen atoms to a compound or element. The presence of a catalyst is usually required for hydrogenation reactions to occur; non-catalytic hydrogenation takes place only at extreme temperatures.
In these enzymes, both substrates bind to the enzyme at the same time to produce an EAB ternary complex. The order of binding can either be random (in a random mechanism) or substrates have to bind in a particular sequence (in an ordered mechanism). When a set of v by [S] curves (fixed A, varying B) from an enzyme with a ternary-complex mechanism are plotted in a Lineweaver–Burk plot, the set of lines produced will intersect. Enzymes with ternary-complex mechanisms include glutathione S-transferase, dihydrofolate reductase and DNA polymerase. Substituted-enzyme ("ping–pong") mechanisms
Sources: en.wikipedia.org
== Solesta == Solesta is the marketed brand name of a system of injections of dextranomer in stabilized sodium hyaluronate for use in fecal incontinence (FI). This preparation is a biocompatible gel, for use as a perianal injectable bulking agent. The system is intended to be injected in the submucosal layer of the proximal anal canal (i.e. above the level of the dentate line).
The two substrates of this enzyme are (S)-malic acid and oxidised nicotinamide adenine dinucleotide (NAD+). Its products are pyruvic acid, carbon dioxide, and reduced NADH. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (S)-malate:NAD+ oxidoreductase (oxaloacetate-decarboxylating). Other names in common use include malic enzyme, pyruvic-malic carboxylase, NAD+-specific malic enzyme, NAD+-malic enzyme, and NAD+-linked malic enzyme. This enzyme participates in pyruvate metabolism.
== The Strep-tag principle == Just like other short-affinity tags (His-tag, FLAG-tag), the Strep-tag can be easily fused to recombinant proteins during subcloning of its cDNA or gene. For its expression, various vectors for various host organisms (E. coli, yeast, insect, and mammalian cells) are available. A particular benefit of the Strep-tag is its rather small size and the fact that it is biochemically almost inert. Therefore, protein folding or secretion is not influenced and usually it does not interfere with protein function. Strep-tag is especially suited for analysis of functional proteins, because the purification procedure can be kept under physiological conditions. This not only allows the isolation of sensitive proteins in a native state, but it is also possible to purify intact protein complexes, even if just one subunit carries the tag. In the first step of the Strep-tag purification cycle, the cell lysate containing Strep-tag fusion protein is applied to a column with immobilized Strep-Tactin (step 1). After the tagged protein has specifically bound to Strep-Tactin, a short washing step with a physiological buffer (e.g. phosphate buffered saline, PBS) removes all other host proteins (step 2). This is due to Strep-Tactin's low tendency to bind proteins non specifically. Then, the purified Strep-tag fusion protein is gently eluted with a low concentration of desthiobiotin, which specifically competes for the biotin binding pocket (step 3). To regenerate the column, desthiobiotin is removed by application of a HABA containing solution (a yellow azo dye).
In many-body potentials, the potential energy includes the effects of three or more particles interacting with each other. In simulations with pairwise potentials, global interactions in the system also exist, but they occur only through pairwise terms. In many-body potentials, the potential energy cannot be found by a sum over pairs of atoms, as these interactions are calculated explicitly as a combination of higher-order terms. In the statistical view, the dependency between the variables cannot in general be expressed using only pairwise products of the degrees of freedom. For example, the Tersoff potential, which was originally used to simulate carbon, silicon, and germanium, and has since been used for a wide range of other materials, involves a sum over groups of three atoms, with the angles between the atoms being an important factor in the potential. Other examples are the embedded-atom method (EAM), the EDIP, and the Tight-Binding Second Moment Approximation (TBSMA) potentials, where the electron density of states in the region of an atom is calculated from a sum of contributions from surrounding atoms, and the potential energy contribution is then a function of this sum.
Sources: en.wikipedia.org
It is often estimated by TNBS, OPA, or pH-stat methods that quantify free amino groups or released protons. Values depend on assay conditions, protein standard, and calculation method. No single universal protocol exists for all products.
It shows the relative amounts of peptides in different size ranges, commonly by size-exclusion chromatography or SDS-PAGE. A lower average weight indicates more extensive hydrolysis. It does not identify specific peptide sequences or biological effects.
No. Immunoassays can measure residual protein or specific whey proteins, but hypoallergenicity requires clinical evaluation. Hydrolysis may reduce IgE-binding, yet some peptides can remain reactive. Label claims are regulated separately from analytical results.
Hydrolysate has undergone enzymatic cleavage of peptide bonds, while isolate is largely intact protein. Both can originate from the same whey stream, but hydrolysis changes peptide size, solubility, taste, and allergenicity testing outcomes. The two ingredients are not interchangeable in every formulation.