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 2026-08-01 and is reviewed periodically as new material appears.
Physical properties such as particle size, bulk density, and reconstitution behavior affect handling and finished product quality. Water activity and moisture content influence shelf life; high moisture can promote caking, browning, and microbial growth. Color is monitored because Maillard reactions between peptides and reducing sugars can darken the powder during storage. Taste panels and instrumental methods may assess bitterness, which is a common challenge for hydrolysates. Specifications often include limits for heavy metals, microbiological counts, and residual fat, depending on the intended market.
Quality control for hydrolyzed whey protein focuses on composition, peptide size, and batch consistency. Protein content is commonly measured by Kjeldahl or combustion analysis, while moisture and ash are determined by gravimetric methods. Peptide molecular weight distribution is often assessed by size exclusion chromatography or mass spectrometry. The extent of hydrolysis can be estimated by titration, trinitrobenzenesulfonic acid assays, or formol titration. Because hydrolysis produces a complex mixture, no single test captures every relevant property, and laboratories often combine several methods.
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.
Degree of hydrolysis is commonly estimated by titrating liberated carboxyl groups, measuring soluble nitrogen in trichloroacetic acid, or using o-phthaldialdehyde assays. Molecular weight distribution is often examined by size-exclusion chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis, or mass spectrometry. These methods answer different questions: titration estimates bond cleavage, while chromatography describes peptide size ranges. Because no single reference method is universally applied, values reported by different laboratories may not be directly comparable. Method details such as calibration standards and sample preparation strongly influence results.
| Property | Value | Notes |
|---|---|---|
| Moisture content | Typically 3-7% | Higher moisture increases caking and browning risk |
| Water activity | Usually below 0.6 | Low water activity limits microbial growth |
| Storage temperature | 15-25 °C, dry conditions | Cool, dry storage slows quality loss |
| Peptide size method | Size exclusion chromatography | Calibration standards affect reported molecular weight |
| Allergen labeling | Milk declaration often required | Rules vary by jurisdiction and product type |
Laboratories characterize whey protein hydrolysate using several complementary methods. Nitrogen determination estimates total protein, while size-exclusion chromatography and mass spectrometry reveal peptide size distributions. Degree of hydrolysis can be calculated from free amino groups, pH change, or osmolarity, but each approach has assumptions. Moisture, ash, and mineral content are also measured because they affect shelf life and reconstitution. No single test fully describes a hydrolysate, so specifications usually combine several results.
Storage stability depends on moisture, temperature, and exposure to oxygen. Dry hydrolysate powders are hygroscopic and can clump or cake when humidity is high. Moisture also promotes Maillard reactions between peptides and residual lactose, leading to browning and flavor changes. Cool, dry, sealed storage slows these reactions, while prolonged warmth can increase off-flavors and reduce solubility. Stability studies often track color, moisture, free amino groups, and microbial load over time to estimate shelf life.
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.
Peptide size distribution is central to product characterization because biological and functional effects often depend on molecular weight. Size-exclusion chromatography, reversed-phase high-performance liquid chromatography, and capillary electrophoresis can separate peptides by size or hydrophobicity. Mass spectrometry provides sequence-level information and can detect marker peptides, though it is less common for routine lot release. For allergen control, enzyme-linked immunosorbent assays estimate residual intact protein or specific milk proteins, but results depend on antibody recognition and may not detect small peptides. No single method captures the full composition.
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.
Analytical control focuses on protein content, hydrolysis extent, molecular weight distribution, and residual intact protein. Kjeldahl or Dumas methods measure total nitrogen, while size-exclusion chromatography or mass spectrometry estimates peptide profiles. Sodium dodecyl sulfate polyacrylamide gel electrophoresis can show remaining intact proteins, though small peptides may not resolve. Enzyme-linked immunosorbent assays are used to assess residual allergenic proteins in some contexts. Because no single method captures all relevant features, manufacturers combine several assays and report values against internal specifications.
Stability depends on moisture, temperature, oxygen, and packaging. Powdered hydrolysate generally requires cool, dry storage and protection from humidity because peptides can absorb water and undergo Maillard reactions with residual lactose. Higher temperatures can increase bitterness, discoloration, and loss of solubility over time, while liquid hydrolysate formats are more perishable and may need refrigeration or preservatives. Shelf-life studies typically monitor moisture, color, pH, protein solubility, and microbial counts. Exact stability limits vary by peptide profile, packaging, and water activity, so general rules should be treated as approximate.
=== Single-locus sequence typing === Single-locus sequence typing (SLST) is the sequencing of a single locus of an organism to produce data that can be used for strain-level comparisons between isolates of the same species.
Both the new Law of Political Parties and the process of illegalization of Batasuna were strongly contested by the Basque nationalist parties and, as an alternative, the lehendakari Juan José Ibarretxe proposed a "pacification plan" based on the holding of a referendum regulating "the free association of Euskadi to the plurinational Spanish State". By the end of 2003, the tension between the central government and the "peripheral" nationalisms moved to Catalonia as a result of the formation of a left-wing "tri-party" government after the Catalan elections of November 2003 consisting of the Socialists' Party of Catalonia (PSC), Republican Left of Catalonia (ERC, a pro-independence party that had experienced a meteoric rise), and Initiative for Catalonia Greens (a party associated with United Left) and presided by the socialist Pasqual Maragall. The "Tinell Pact" of the PSC-PSOE, IC and ERC (in which the "tri-party" program was agreed, expressly excluding any agreement with the PP) was harshly criticized by the Aznar government and by the new PP leader Mariano Rajoy ─ who at the end of August 2003 had been proposed by Aznar to replace him as candidate in the following year's elections. By the end of January 2004, a scandal broke out that shook the "tri-party" government. In its 24th edition, the newspaper "ABC" published that the leader of ERC, Josep Lluís Carod Rovira, conseller en cap of the Generalitat, had met in Perpignan with the top leadership of ETA to negotiate an exclusive truce for Catalonia.
== South Africa == In 1996 the main laboratory moved to Richmond and could provide services to the Gauteng region. In 2000 it merged with the Pillay MacIntosh practice in Durban. Eftyhia Vardas is the head of virology at the Lancet in Johannesburg. In November 2021, Alison J. Glass, a clinical virologist at the lab reported that observations made by one of their junior scientists led to the discovery of the omicron variant of the COVID-19 virus. The laboratory sent samples to the Network for Genomic Surveillance in South Africa, of which the Lancet is a part and whose principal investigator, Tulio de Oliveira, confirmed and announced the findings following further investigation.
DCC (acronym for N,N'-dicyclohexylcarbodiimide) was one of the first carbodiimides developed as a reagent. It is widely used for amide and ester formation, especially for solid-phase synthesis of peptides. DCC has achieved popularity mainly because of its high-yielding amide coupling reactions and the fact that it is quite inexpensive. However, DCC does have some serious drawbacks, and its use is often avoided for several reasons:
Sources: en.wikipedia.org
== Regulation == Bassoon protein and pLG72, are the current known proteins to physically interact and modulate human DAAO. plG72 is the product of the primate-specific G72 gene, and higher levels of both were observed in schizophrenia patients. Interaction of plG72 with hDAAO was observed to cause a time-dependent inactivation with the oxidase. This is believed to be caused by plG72 binding limiting the amount of the enzyme that is catalytically competent, and can be negated by the cofactor or any active-site ligands. The plG72 structure is not fully determined so the specific physical interaction with hDAAO is not completely understood as well. Experiments with the basson protein and hDAAO has resulted with a decrease in enzymatic activity similar to plG72. Researchers suspect the bassoon protein prevents D-serine depletion particularly in the presynaptic neuron. Additionally, researchers focused on compounds that could act as hDAAO inhibitors. Over 500 different compounds have been observed in vitro/in vivo to act as inhibitors on the oxidase and most of them do by competitive inhibition. All of these compounds have two similar, main portions. The first portion is the planar portion which interacts with the active site of hDAAO. The planar site’s chemical structure is formed by one or two fused rings and must have a negatively charged carboxylic group. The second portion is the substrate chain, which can participate in the active zone or entrance of the enzyme.
=== Sales === Antipsychotics were once among the biggest selling and most profitable of all drugs, generating $22 billion in global sales in 2008. By 2003 in the US, an estimated 3.21 million patients received antipsychotics, worth an estimated $2.82 billion. Over 2/3 of prescriptions were for the newer, more expensive atypicals, each costing on average $164 per year, compared to $40 for the older types. By 2008, sales in the US reached $14.6 billion, the biggest selling drugs in the US by therapeutic class. In the five years since July 2017 the number of antipsychotic medicines dispensed in the community in the United Kingdom has increased by 11.2%. There have also been substantial price rises. Risperidone 6 mg tablets, the largest, increased from £3.09 in July 2017 to £41.16 in June 2022. The NHS is spending an additional £33 million annually on antipsychotics. Haloperidol 500 microgram tablets constituted £14.3 million of this.
2(Ag(NH3)2)+ + RCHO + 2OH− → RCOOH + 2Ag + 4NH3. The size and shape of the nanoparticles produced are difficult to control and often have wide distributions. However, this method is often used to apply thin coatings of silver particles onto surfaces and further study into producing more uniformly sized nanoparticles is being done.
Sources: en.wikipedia.org
Size exclusion chromatography separates peptides by molecular size in solution, and mass spectrometry can provide more detailed mass information. Results are usually reported as a distribution rather than a single value. Method choice and calibration affect the reported range.
Many allergen tests rely on antibodies that bind intact milk proteins, and hydrolysis can remove or change those binding sites. A negative result may therefore reflect lost detection rather than absence of milk-derived material. Confirmatory methods and labeling rules are needed for reliable assessment.
Bitterness often comes from short peptides that contain hydrophobic amino acids. These peptides can interact with bitter taste receptors on the tongue. The intensity depends on the enzyme, degree of hydrolysis, and peptide profile.
Peptide size is commonly estimated by size-exclusion chromatography, gel electrophoresis, or mass spectrometry. These techniques separate or identify molecules according to mass or hydrodynamic volume. Results depend on calibration and method conditions, so they are best compared within the same analytical protocol.