A practical reference on Water activity: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-24 and is reviewed periodically as new material appears.
Whey protein hydrolysate is a dairy ingredient made by breaking peptide bonds in whey proteins. Enzymes such as proteases, or in some processes acid or heat, cleave the protein chains into shorter peptides and free amino acids. The starting material may be sweet whey, acid whey, whey protein concentrate, or whey protein isolate. Because raw materials and reaction conditions differ, the final mixture is not a single uniform substance. Its peptide profile, mineral content, and residual lactose depend on the source and the processing steps used.
Production typically begins with pasteurization and concentration of whey. A protease is added under controlled temperature and pH, and the reaction is stopped by heat or pH change when the target extent of cleavage is reached. Ultrafiltration or diafiltration may remove enzymes, salts, and small molecules. The liquid is then spray dried into a powder. Process parameters shape bitterness, solubility, and peptide size. Established control points include enzyme type, reaction time, and inactivation conditions. How these variables interact across large-scale batches remains an area of active process development.
Hydrolysates usually contain 70% to 90% protein on a dry basis, with variable ash, fat, and carbohydrate. Solubility in water is generally high over a broad pH range, though bitter notes can appear from exposed hydrophobic peptides. The powder tends to absorb moisture and may brown during prolonged warm storage. Applications span sports nutrition, clinical nutrition, infant formulas, and flavor systems. Regulatory status and labeling rules differ by country. A key open question is whether a given peptide profile reliably predicts functional or sensory behavior across different food matrices.
Laboratories characterize whey protein hydrolysate by several complementary methods. Total nitrogen or Kjeldahl analysis estimates crude protein, while amino acid analysis gives a more detailed composition. Size-exclusion chromatography and mass spectrometry separate peptides by molecular weight and can reveal the distribution of chain lengths. Degree of hydrolysis is often calculated from free amino groups using trinitrobenzenesulfonic acid or o-phthaldialdehyde assays. No single measurement captures all relevant properties, so specifications usually combine protein content, peptide profile, moisture, ash, and microbial limits.
Storage stability depends on moisture, temperature, oxygen, and packaging. Dry hydrolysate powders are typically stable for months to years when kept cool and sealed, but they can absorb water and cake if exposed to humid air. Higher temperatures accelerate Maillard reactions between peptides and residual sugars, leading to browning and flavor changes. Lipid oxidation can occur if residual fat is present, producing off-odors. Once a powder is reconstituted, microbial growth becomes a concern, so liquid forms require refrigeration or other preservation steps.
| Property | Value | Notes |
|---|---|---|
| Appearance | Off-white to pale yellow powder | Color varies with whey source and drying. |
| Protein content | 75–90% of dry matter | Depends on raw material and filtration. |
| Hydrolysis extent | 5–35% cleaved bonds | Ranges overlap product types; assay-dependent. |
| Water solubility | High across pH 3–7 | Hydrolysis raises solubility versus intact protein. |
| Typical storage | 15–25 °C, dry | Keep sealed; limit moisture and heat. |
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.
Industrial production begins with whey protein concentrate or isolate dispersed in water. Selected proteases, such as trypsin, pepsin, or microbial enzymes, are added under controlled pH and temperature. Hydrolysis continues until a target hydrolysis level is reached, after which heat or pH adjustment inactivates the enzyme. Ultrafiltration, diafiltration, and ion exchange may remove larger peptides, salts, or residual lactose. The liquid is then concentrated and spray-dried into powder. Processing choices influence peptide size, bitterness, mineral content, and microbial quality.
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.
Production usually starts with whey protein concentrate or isolate. The material is dissolved, pasteurized, and adjusted to conditions that favor a chosen protease, such as trypsin, pepsin, or papain. Enzyme choice, pH, temperature, and reaction time determine peptide length, terminal residues, and functional behavior. After hydrolysis, the enzyme is inactivated by heat or pH change, and the liquid is clarified, filtered, concentrated, and dried. Membrane filtration can further fractionate peptides and remove some minerals or lactose. The final powder is typically spray-dried.
Composition reflects the whey source and the extent of hydrolysis. Beta-lactoglobulin and alpha-lactalbumin fragments are common, and sweet whey may contribute glycomacropeptide. The amino acid profile remains broadly similar to intact whey protein, but peptide size affects how quickly nitrogen appears in blood after ingestion. Bitter notes often arise from short peptides with hydrophobic residues. Hydrolysates are used in sports nutrition, infant formula, and clinical nutrition, though effects on muscle, immunity, or allergy risk are separate research questions rather than guaranteed properties.
=== Mentor === Hodgkin's mentor Professor John Desmond Bernal greatly influenced her life: scientifically, politically, and personally. Bernal was a key scientific adviser to the UK government during the Second World War. He was also an open and vocal member of the Communist Party and a faithful supporter of the Soviet regime until its invasion of Hungary in 1956. He was a chemist who believed in equal opportunity for women. In his laboratory, Hodgkin extended work that he began on biological molecules including sterols. She helped him to make the first X-ray diffraction studies of pepsin and crystalline protein. Hodgkin always referred to him as "Sage". They were lovers before she met Thomas Hodgkin. The marriages of both Dorothy and Bernal were unconventional by the standards of the present and of those days.
The division mobilized to the Clermont area in Argonne, just west of Verdun, starting on 24 September, stationed there to act as a reserve for the US First Army. On 3 October, Major General George B. Duncan, commander of the 77th Division, relieved William Burnham of his duties and took over as commander of the 82nd. On the night of 6 October 1918, the 164th Brigade relieved troops of the 28th Division, which were holding the front line from south of Fléville to La Forge, along the eastern bank of the Aire River. On 7 October, the 82nd Division, minus the 163rd Brigade, which remained in reserve, attacked the northeastern edge of the Argonne Forest, taking "Hill 223" in the process. The division's right flank entered the commune of Cornay but later withdrew southeast. The division's left flank took the high ground northwest of Châtel-Chéhéry. On 9 October, the division's left flank advanced to form a line along the French pylons on the road to the Belgian city of la Louvière. Throughout October, the division advanced north-east along the Aire (Aisne) river. On 10 October, it relieved troops of the 1st Division in Ardennes at Fléville and Sommerance. The 82nd Division then relaunched an attack on Cornay and the Belgian city of Enghien, successfully re-establishing the front there. On 11 October, the right flank of the division took the high ground north of the Rance river while the left flank continued to advance along the Aire. The next day, the 42nd Division relieved the 82nd's troops in Sommerance.
Ceruloplasmin is the major copper-carrying protein in the blood. Ceruloplasmin exhibits oxidase activity, which is associated with possible oxidation of Fe(II) into Fe(III), therefore assisting in its transport in the blood plasma in association with transferrin, which can carry iron only in the Fe(III) state.
Sources: en.wikipedia.org
=== Receptor autoradiography === The use of radiolabeled ligands to determine the tissue distributions of receptors is termed either in vivo or in vitro receptor autoradiography if the ligand is administered into the circulation (with subsequent tissue removal and sectioning) or applied to the tissue sections, respectively. Once the receptor density is known, in vitro autoradiography can also be used to determine the anatomical distribution and affinity of a radiolabeled drug towards the receptor. For in vitro autoradiography, radioligand was directly applying on frozen tissue sections without administration to the subject. Thus it cannot follow the distribution, metabolism and degradation situation completely in the living body. But because target in the cryosections is widely exposed and can direct contact with radioligand, in vitro autoradiography is still a quick and easy method to screen drug candidates, PET and SPECT ligands. The ligands are generally labeled with 3H (tritium), 18F (fluorine-18), 11C (carbon-11) or 125I (radioiodine). Compare to in vitro, ex vivo autoradiography were performed after administration of radioligand in the body, which can decrease the artifacts and are closer to the inner environment. The distribution of RNA transcripts in tissue sections by the use of radiolabeled, complementary oligonucleotides or ribonucleic acids ("riboprobes") is called in situ hybridization histochemistry.
The IDF is planning a number of technological upgrades and structural reforms for the future. Training has been increased with greater cooperation between ground, air, and naval units. The Ground Forces are phasing out the M-16 rifle in favor of the IWI Tavor variants, most recently the IWI Tavor X95 flat-top ("Micro-Tavor Dor Gimel"). The outdated M113 armored personnel carriers are being replaced by the new Namer APCs, with 200 ordered in 2014, as well as obtaining the Eitan AFV, and upgrading the IDF Achzarit APCs. The backbone of the Artillery Corps, the M109 howitzer, will be phased out in favor of a still-undecided replacement, with the ATMOS 2000 and Artillery Gun Module under primary consideration. The IDF is planning a future tank to replace the Merkava, which will be able to fire lasers and electromagnetic pulses, run on a hybrid engine, with a crew as small as two, will be faster, and will be better-protected, with emphasis on active protection systems such as the Trophy over armor. The Combat Engineering Corps assimilated new technologies, mainly in tunnel detection and unmanned ground vehicles and military robots, such as remote-controlled IDF Caterpillar D9T "Panda" armored bulldozers, Sahar engineering scout robot and improved Remotec ANDROS robots.
Treatment for thalassemia depends on the severity of the disease. People with thalassemia traits (thalassemia minor or non transfusion dependent thalassemia), may not require medical or follow-up care after the initial diagnosis is made. Occasionally transfusions may be necessary particularly around childbirth, surgery, or if other conditions provoke anemia. A folic acid supplement may also be recommended. For those with severe forms of thalassemia (thalassemia major, or transfusion-dependent thalassemia), the three principal treatments are red blood cell transfusions to relieve anemia, iron chelation to mitigate the side effects of transfusion, and folic acid supplementation to encourage the growth of new blood cells. Other forms of treatment available depending on individual circumstances.
Sources: en.wikipedia.org
Hydrolysis extent indicates the share of peptide bonds that have been cleaved. It is often estimated from free amino groups and is reported as a percentage. A higher value means smaller peptides and more free amino acids, but it does not by itself define product quality.
No. Whey protein isolate is a filtered protein ingredient with most lactose and fat removed. Hydrolysate refers to protein that has been treated to break peptide bonds, and it can be made from isolate, concentrate, or whey itself.
Not directly. Lactose content depends mainly on the starting material and filtration steps. A hydrolysate made from isolate is typically lower in lactose than one made from sweet whey.
Degree of hydrolysis is commonly estimated by quantifying free amino groups with colorimetric assays such as o-phthaldialdehyde or trinitrobenzenesulfonic acid. The result is expressed as a percentage of total peptide bonds cleaved. Because different assays can give different values, method details matter when comparing products.