Dairy and whey ingredients glossary

A powder-processing step in which fine particles are brought together to form larger, more porous granules. In dairy powders, agglomeration is used to improve wettability, dispersibility, flowability and instantisation, particularly for products such as milk powders, WPC, WPI and nutritional powders. The resulting particle structure and size distribution can strongly influence reconstitution behaviour, dusting, bulk density and handling performance.

The ratio between the concentration of a component in the retentate and its concentration in the original feed, or, depending on context, the ratio of feed volume to final retentate volume. In membrane processing, it indicates how far a stream has been concentrated and is important because increasing concentration affects viscosity, flux, pressure drop, fouling tendency and achievable solids content.

A membrane filtration configuration in which the feed flows parallel to the membrane surface, while part of the liquid passes through the membrane as permeate. The remaining stream continues along the membrane as retentate. This flow pattern helps reduce the build-up of material on the membrane surface compared with dead-end filtration.

A membrane-processing step in which water is added to the retentate during ultrafiltration to wash out smaller soluble components, such as lactose and minerals, while retaining larger components such as proteins. It is commonly used in dairy protein processing to increase protein purity and reduce lactose and mineral content.

A thermal concentration process used to remove water from liquid dairy streams before further processing or drying. In dairy manufacturing, evaporation is widely used for milk, whey, permeate and protein concentrates, reducing the water load on spray dryers and improving overall energy efficiency. Product temperature, residence time and solids concentration must be carefully controlled because excessive heat exposure can affect protein functionality, flavour, viscosity and fouling.

A drying and cooling process in which powder particles are suspended and mixed by an upward flow of air, creating a fluid-like bed. In dairy powder manufacture, fluid beds are commonly used after spray drying to remove the final portion of moisture, cool the powder and improve agglomeration, flowability and particle size distribution. Compared with completing all drying in the spray drying chamber, fluid bed drying can reduce heat exposure and improve energy efficiency and powder quality.

The build-up of proteins, minerals, fat or other material on the membrane surface or within its pores during filtration, which increases resistance to flow and can reduce flux and separation efficiency. Fouling can be limited through appropriate cross-flow velocity, temperature and pressure control, feed pre-treatment, regular cleaning-in-place (CIP), and effective membrane cleaning procedures.

A powder processing treatment used to improve how quickly and easily a dairy powder reconstitutes in water. It commonly combines agglomeration with surface treatment, such as lecithination, to improve wettability, dispersibility and reduce floating or clumping. Instantisation is particularly important for products such as WPC, WPI, milk powders and nutritional powders, where consumer preparation and rapid dissolution are critical quality attributes.

A separation process in which charged ions in a liquid are exchanged with ions bound to an ion-exchange resin. In dairy processing, it is commonly used for demineralisation, purification and selective removal of charged components, including in the production of demineralised whey and specialised protein ingredients.

The controlled formation of crystals from a supersaturated solution. In dairy processing, crystallisation is particularly important for lactose recovery from whey or permeate and for controlling lactose behaviour before drying. Crystal formation is influenced by factors such as concentration, temperature, cooling rate, seeding and agitation, and poor control can affect yield, powder stability and downstream processing performance.

A powder surface treatment process in which lecithin (commonly soya or sunflower) is applied to improve wettability and dispersibility, particularly in high protein or high-fat powders that can be difficult to reconstitute. It is commonly used during instantisation of WPC, WPI and nutritional powders. The type and level of lecithin, application method and powder characteristics influence reconstitution performance, flavour and overall product quality.

A calculation used to track the quantity of material entering, leaving and remaining within a process, based on the principle that mass is conserved. In dairy processing, mass balances are used to quantify product yields, component recoveries, losses and the distribution of constituents such as protein, fat, lactose and minerals across different process streams. They are important for process design, yield optimisation, troubleshooting, loss identification, production planning and evaluating the economic value of different processing routes.

The replaceable filtration unit installed within a membrane housing, containing the membrane through which separation takes place. Common configurations include spiral-wound, tubular, hollow-fibre and plate-and-frame elements. In dairy processing, spiral-wound elements are widely used because they provide high membrane area in a compact format, while more open-channel designs may be preferred for viscous or fouling-prone streams. Element selection affects pressure drop, cleanability, fouling tendency, flux and overall plant capacity, so the choice of configuration must reflect both the separation objective and the characteristics of the feed stream.

The use of membrane filtration to separate milk or whey components according to differences such as molecular size, permeability and interactions with the membrane. In dairy processing, it is used to enrich or separate fractions such as whey proteins, casein, lactose, minerals and specific protein populations. Successful fractionation depends on membrane type, pore size or molecular weight cut-off, operating conditions and feed composition, all of which influence selectivity, yield and purity.

A membrane separation process using relatively large membrane pores compared with ultrafiltration, allowing water, lactose, minerals and many whey proteins to pass while retaining larger components such as bacteria, fat globules and casein micelles, depending on the application. In dairy processing, Microfiltration (MF) is widely used for bacteria reduction, milk protein fractionation, casein concentration and whey defatting. Performance is strongly influenced by pore size, temperature, cross-flow conditions and fouling control.

Molecular weight cut-off (MWCO) is a nominal membrane rating indicating the approximate molecular mass above which a defined proportion of a solute is retained. It is mainly used to compare ultrafiltration membrane selectivity rather than as an absolute separation boundary.

A membrane separation process positioned between ultrafiltration and reverse osmosis, used to concentrate dairy streams while allowing part of the water and monovalent minerals to pass through the membrane. In dairy processing, nanofiltration (NF) is commonly used for whey and permeate concentration, partial demineralisation and volume reduction before evaporation or drying. Its value lies in combining concentration with selective mineral removal, although performance depends strongly on membrane selectivity, osmotic pressure, feed composition and fouling control.

The liquid fraction that passes through a membrane during filtration. In dairy processing, permeate typically contains lactose, minerals, water and other small soluble components, while most proteins and larger molecules are retained in the retentate. Its composition depends on the starting material and the membrane process used.

The rate at which permeate passes through a membrane per unit of membrane area, usually expressed as litres per square metre per hour (L/m²·h). Flux is influenced by factors such as transmembrane pressure, temperature, viscosity, membrane properties, concentration and fouling, and is a key measure of membrane filtration performance.

he proportion of protein in the original feed that is recovered in the target product or retentate, usually expressed as a percentage. In dairy processing, protein recovery is a key measure of process performance because even small losses can have a significant impact on product yield, raw material utilisation and manufacturing economics. Recovery is influenced by membrane selectivity, processing conditions, diafiltration, fouling and protein losses into permeate or other side streams.

A measure of how effectively a membrane retains a particular component rather than allowing it to pass into the permeate. It is typically calculated from the difference between the component concentration in the feed and permeate and expressed as a fraction or percentage. In dairy processing, high rejection is desirable when retaining valuable components such as proteins, while lower rejection may be preferred for components intended to pass through the membrane, such as lactose or minerals. The value depends on membrane selectivity, operating conditions, concentration and interactions between the component and membrane.

The fraction of a feed stream that is retained by a membrane during filtration because its components are too large, or otherwise unable, to pass through the membrane. In dairy processing, retentate is typically enriched in proteins, fat or other larger components, depending on the membrane type and process objective. Its increasing concentration during processing affects viscosity, flux, pressure drop and overall plant performance.

A pressure-driven membrane process that removes water from a dairy stream while retaining most dissolved solids, including lactose, proteins and minerals. In dairy processing, reverse osmosis (RO) is commonly used for pre-concentration of milk, whey and permeate before evaporation or drying, helping reduce the volume of water that must be removed thermally. Its performance is strongly influenced by osmotic pressure, feed concentration, temperature, fouling and the maximum solids level achievable before flux declines significantly.

A drying process in which a concentrated liquid feed is atomised into fine droplets and contacted with hot air to rapidly remove water and produce a powder. In dairy processing, spray drying is widely used for milk powders, whey powders, WPC, WPI and nutritional ingredients. Feed solids, inlet and outlet air temperatures, atomisation conditions and dryer configuration strongly influence moisture, particle size, bulk density, solubility, heat damage and overall powder functionality.

A pressure-driven membrane process used to separate and concentrate larger molecules such as proteins, while allowing water, lactose, minerals and other smaller components to pass into the permeate. In dairy processing, UF is widely used to manufacture WPC, WPI, MPC and other protein concentrates. Membrane selection, concentration factor, diafiltration and fouling control all influence protein recovery, purity, flux and final product functionality.

The liquid by-product generated when milk is coagulated by acidification rather than rennet, such as in the manufacture of Greek-style yoghurt, cottage cheese, Skyr and some fresh cheeses. Compared with sweet whey, acid whey has a lower pH, higher mineral content and a different calcium and phosphate balance, which can make it more challenging to process and valorise. Its composition and acidity affect membrane performance, concentration, drying behaviour and ingredient functionality, so successful utilisation often requires careful process design rather than simply applying conventional sweet-whey processing routes.

A functional milk protein ingredient produced by neutralising acid casein with an alkali, commonly to form sodium caseinate, calcium caseinate or potassium caseinate. Neutralisation converts the relatively insoluble acid casein into a more dispersible and functional ingredient. Caseinates are valued for their emulsification, water binding, viscosity and protein enrichment and are used in applications such as nutritional products, beverages, processed foods and specialised formulations. Their functionality can vary significantly with the type of cation used, processing conditions and final mineral balance.

The principal group of proteins in bovine milk, accounting for about 80% of total milk protein. Casein exists naturally as micelles containing casein fractions associated with calcium and phosphate. In dairy processing, casein is important because its structure and mineral interactions strongly influence coagulation, heat stability, texture and protein functionality. It can also be separated from milk to produce ingredients such as acid casein, rennet casein and caseinates.

A term commonly used for whey protein ingredients or beverages formulated to produce a clear or translucent drink rather than the opaque, milk-like appearance of conventional whey protein shakes. Clear whey products are typically based on highly purified whey proteins, often whey protein isolate, formulated under acidic conditions where the protein can remain soluble and visually clear. Achieving good clarity depends on factors such as protein state, pH, mineral content, heat treatment andprocessing conditions, and poor control can lead to haze, precipitation or loss of protein stability.

Whey from which a proportion of the naturally occurring minerals has been removed, typically using electrodialysis, ion exchange, nanofiltration or combinations of these processes. Demineralisation reduces ash and specific mineral levels, improving flavour and making the ingredient more suitable for applications where mineral composition is tightly controlled, particularly infant formula and specialised nutrition. In practice, the target degree of demineralisation affects not only composition but also processing cost, mineral balance, taste and downstream functionality. Commercial products are often described by their degree of demineralisation, for example D40, D50, D70 or D90, indicating approximately 40%, 50%, 70% or 90% mineral removal relative to the original whey.

A glycosylated peptide released from κ-casein during rennet coagulation in cheesemaking. Because GMP remains in the liquid phase, it becomes part of sweet whey and can subsequently be concentrated or isolated during whey processing. GMP has a distinctive amino acid profile, including very low levels of phenylalanine, which makes highly purified GMP particularly relevant to specialised nutritional applications such as products for people with phenylketonuria (PKU). Its recovery also depends strongly on the whey source and downstream fractionation process.

A protein- and fat-rich whey ingredient produced as a side stream during the manufacture of low-fat WPC or WPI, typically from microfiltration retentate. It contains whey proteins together with concentrated fat, phospholipids and milk fat globule membrane components, giving it different nutritional and functional properties from conventional WPC. It is also known as whey protein phospholipid concentrate (WPPC) and can be used in nutritional and food applications where protein, emulsification and phospholipid content add value.

A group of antibody proteins naturally present in milk and whey that form part of the immune system. The main immunoglobulins found in bovine milk are IgG, IgA and IgM, with IgG1 being the predominant form. Their concentrations are much higher in colostrum than in mature milk, and they are of interest in specialised nutrition and functional ingredient applications because of their biological activity.

An iron-binding glycoprotein naturally present in milk, whey and especially colostrum. It is valued for its iron-binding, antimicrobial and immune-related biological functions and is used in high-value applications such as infant formula, specialised nutrition and functional foods. Because lactoferrin is present at relatively low concentrations in bovine milk, its commercial recovery typically relies on selective separation and purification processes.

The naturally occurring sugar in milk, composed of glucose and galactose. In dairy processing, lactose is recovered mainly from whey or whey permeate and is used in infant nutrition, food and pharmaceutical applications. Commercial lactose grades are differentiated by factors such as purity, crystal form and particle size distribution, which influence properties including flowability, dissolution and processing performance.

Casein in its native micellar form, as it occurs naturally in milk. It is typically concentrated from skim milk using membrane filtration while largely retaining the original casein micelle structure and associated minerals. Micellar casein is valued for its high protein content, slow digestion profile and functional properties, and is widely used in sports nutrition, clinical nutrition and other high protein applications.

A concentrated milk protein ingredient produced by removing part of the water, lactose and minerals from skim milk, typically using membrane filtration. MPC contains both casein and whey proteins in approximately the same ratio as milk. Commercial grades typically range from around 40% to 85% protein on a dry matter basis, with common products including MPC40, MPC70, MPC80 and MPC85. It is used in dairy, nutritional and high protein food applications for both its nutritional value and functional properties.

A highly concentrated milk protein ingredient produced from skim milk, typically using membrane filtration and further purification steps. MPI contains both casein and whey proteins in approximately the same ratio as milk and generally contains at least 90% protein on a dry matter basis. It is used in sports nutrition, clinical nutrition, dairy and other high protein food applications where high protein content and low levels of lactose and fat are required.

Whey protein recovered directly from milk, usually by microfiltration of skim milk, rather than as a co-product of cheese manufacture. Because it bypasses cheesemaking, it differs from cheese whey in composition and processing history, including the absence of rennet-derived glycomacropeptide.

The liquid by-product produced during manufacture of rennet-coagulated cheeses such as Cheddar, Gouda, Edam and Mozzarella. It typically has a higher pH and lower mineral content than acid whey and contains lactose, whey proteins, minerals and small amounts of fat. Sweet whey is the main raw material used to produce ingredients such as whey powder, WPC, WPI, lactose and demineralised whey, and its composition strongly influences downstream yield and processing performance.

The liquid portion of milk that remains after coagulation and removal of the curd during cheesemaking or casein manufacture. It contains mainly water, lactose, whey proteins, minerals and small amounts of fat. Depending on how it is produced, whey is commonly classified as sweet whey or acid whey and can be further processed into a wide range of dairy ingredients.

The lactose- and mineral-rich fraction that passes through the membrane during ultrafiltration of whey to produce whey protein concentrates or isolates. It contains mainly lactose and minerals, with only small amounts of protein. Whey permeate can be dried and used in food, feed and fermentation applications, or further processed to recover lactose and other components.

Whey protein concentrate (WPC) is produced by removing non-protein constituents from whey, typically using membrane filtration, to increase its protein concentration. Commercial grades vary widely in protein content, with WPC34/35 and WPC80 among the most common.

A whey protein ingredient in which some of the protein has been broken down into smaller peptides through controlled enzymatic hydrolysis. WPH is used in sports nutrition, clinical nutrition and infant nutrition, particularly where rapid digestion or specific nutritional functionality is required. The degree of hydrolysis (DH) indicates the extent to which peptide bonds have been broken; examples include low DH around 3–5%, moderate DH around 10–15%, and more extensive hydrolysis at 20% or above. Higher DH generally produces smaller peptides but can also increase bitterness and alter functionality.

A highly purified whey protein ingredient containing typically 90% or more protein on a dry matter basis, produced through membrane filtration and additional purification steps to remove most of the lactose, fat and minerals. WPI is widely used in sports nutrition, clinical nutrition, clear protein beverages and other high protein applications where high protein purity and low lactose and fat are important. Its functionality depends strongly on processing history, mineral profile and degree of protein denaturation.

The group of soluble proteins that remain in the liquid whey after milk coagulation during cheesemaking. The main whey proteins in bovine milk include β-lactoglobulin, α-lactalbumin, bovine serum albumin and immunoglobulins, together with other minor proteins and peptides. Whey proteins are valued for their high nutritional quality, digestibility and functional properties and are widely used in sports nutrition, clinical nutrition, infant nutrition and food applications.

A high protein grade of whey protein concentrate (WPC) containing approximately 80% protein on a dry matter basis. It is produced by ultrafiltration of whey, often with diafiltration to further reduce lactose and minerals while concentrating the whey proteins. WPC80 is widely used in sports nutrition, clinical nutrition, protein beverages, bars and other high protein foods. Its performance can vary with whey source and processing history, particularly in relation to solubility, heat stability, flavour and protein denaturation.

A major whey protein naturally present in milk and an important component of the whey protein fraction. It has a high nutritional quality and is particularly rich in essential amino acids, including tryptophan. α-Lactalbumin is of particular interest in infant nutrition, clinical nutrition and specialised high-value protein ingredients, partly because it is a major protein in human milk. Commercial α-lactalbumin-enriched ingredients are produced through selective fractionation of whey or milk proteins.

The major whey protein in bovine milk and typically the most abundant protein in the whey protein fraction. It has high nutritional quality and contributes strongly to the gelling, foaming and emulsifying properties of whey protein ingredients. β-Lactoglobulin is also relatively heat-sensitive, so its degree of denaturation can significantly influence the functionality of WPC and WPI in applications such as beverages, nutrition products and high protein foods.

The inorganic fraction of a dairy ingredient remaining after complete combustion of the organic material, commonly reported as ash. It reflects the total mineral content, including components such as calcium, phosphorus, sodium, potassium and magnesium, although ash analysis does not identify individual minerals. In dairy ingredients, mineral composition can influence flavour, solubility, heat stability, nutritional profile and application suitability.

Fatty acids released from triglycerides through lipolysis. In dairy ingredients, elevated free fatty acids (FFA) levels can contribute to rancid, soapy or sharp flavour notes and may indicate fat hydrolysis during processing or storage. Important dairy free fatty acids include butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic and oleic acids. The shorter-chain fatty acids, particularly butyric, caproic, caprylic and capric acids, have a strong sensory impact even at relatively low concentrations.

The protein content of a product expressed after excluding its moisture content. This allows powders with different moisture levels to be compared on an equivalent basis and is commonly used to define commercial dairy protein grades such as WPC80, WPI and MPC. Because moisture can materially affect the reported “as-is” protein percentage, dry-basis values are often more useful for specification, product classification and ingredient comparison.

The proportion of a dairy stream remaining after all water has been removed, including protein, fat, lactose, minerals and other non-water components. Total solids (TS) is a key processing parameter because it influences viscosity, concentration behaviour, evaporation and drying efficiency, product yield and plant capacity. It is commonly expressed as a percentage by weight and is routinely monitored across milk, whey, concentrates and finished powders.

Whey protein nitrogen index (WPNI) is a measure of the undenatured whey protein nitrogen remaining in skim milk powder. It is used primarily to classify milk powders according to the severity of heat treatment during manufacture; higher WPNI indicates less whey protein denaturation.

A dry, puckering or rough mouthfeel sensation caused by interactions between food components and saliva, particularly salivary proteins. In dairy and protein products, astringency can be influenced by protein type and concentration, pH, minerals and heat treatment. It is especially relevant in high protein beverages, where excessive astringency can reduce consumer acceptability even when flavour is otherwise acceptable.

The mass of a powder per unit of bulk volume, including the spaces between particles, typically expressed as kg/m³ or g/mL. In dairy powders, bulk density is influenced by particle size, agglomeration, moisture, powder structure and processing conditions. It is important for packaging efficiency, storage, transport, dosing and powder handling, and can vary substantially between standard and agglomerated or instantised powders.

The formation of hard lumps or a consolidated mass when powder particles stick together during storage or handling. In dairy powders, caking is strongly influenced by moisture uptake, water activity, temperature, hygroscopicity and the physical state of lactose, particularly when amorphous lactose becomes sticky above its glass transition temperature. Caking can reduce flowability, dosing accuracy, reconstitution performance and overall product quality.

The ability of a powder to move freely and consistently during handling, conveying, dosing and packaging. In dairy powders, flowability is influenced by particle size and shape, moisture, fat content, agglomeration, surface properties and storage conditions. Poor flowability can lead to bridging, caking, inconsistent dosing and reduced packing efficiency, so it is an important practical quality attribute for powders such as WPC, WPI, milk powders and nutritional blends.

The ability of a protein system to form foam and the behaviour of that foam over time. In dairy applications, foaming properties are influenced by protein type and concentration, pH, heat treatment, minerals and fat content. The desired performance is application-dependent: stable foam may be required in aerated products, while in ready-to-mix protein beverages rapid foam collapse after shaking is often preferred for better appearance and drinkability.

The formation of a three-dimensional protein network that gives a product structure and can transform a liquid into a gel. In dairy proteins, gelation may be induced by heat, acidification, enzymes or mineral interactions, depending on the protein system. Gelation is important in applications such as yoghurt, desserts, processed foods and high protein products, where it influences texture, water holding and product stability.

The ability of a dairy protein system to withstand thermal processing without excessive denaturation, aggregation, precipitation or loss of functionality. Heat stability is influenced by protein type and concentration, pH, mineral balance, ionic calcium, lactose and processing conditions. It is especially important in UHT beverages, retorted products, evaporated dairy systems and high protein formulations, where poor heat stability can lead to sedimentation, gelation or processing deposits.

The tendency of a powder to absorb moisture from the surrounding air. In dairy powders, hygroscopicity is strongly influenced by composition, particularly amorphous lactose, as well as environmental temperature and relative humidity. Excessive moisture uptake can increase stickiness, caking and loss of flowability, making hygroscopicity an important consideration in powder processing, packaging and storage.

The pH at which a protein has no net electrical charge. At or close to its isoelectric point, protein solubility is generally at its lowest and the tendency to aggregate or precipitate increases. In dairy processing, this is particularly important for casein, which precipitates at around pH 4.6, and for designing acidified dairy or protein beverages where pH strongly affects stability, texture and processing behaviour.

A sensory perception of dryness or reduced lubrication in the mouth during or after consumption. In dairy and high protein products, mouthdrying can arise from interactions between proteins and saliva and may be influenced by protein type and concentration, pH, minerals, heat treatment and formulation. It is particularly relevant in high protein beverages and nutritional products, where excessive mouthdrying can reduce smoothness and overall consumer acceptability.

The overall physical sensation of a food or beverage in the mouth, including attributes such as thickness, creaminess, smoothness, dryness, coating and astringency. In dairy and protein products, mouthfeel is influenced by protein type and concentration, fat, minerals, particle size, viscosity and processing conditions. It is a key quality attribute in beverages, nutritional products and dairy foods because it strongly affects perceived texture and consumer acceptance.

The distribution of particle sizes within a powder, commonly characterised using values such as D10, D50 and D90, which indicate the particle size below which 10%, 50% and 90% of the sample falls. In dairy powders, PSD influences flowability, bulk density, dustiness, wettability, dispersibility and reconstitution behaviour. It is particularly important when comparing standard, agglomerated and instantised powders.

A change in the native structure of a protein caused by factors such as heat, pH, shear or chemical environment, without breaking the primary peptide backbone. In dairy processing, denaturation can alter solubility, aggregation, gelation, emulsification and heat stability. Its impact may be beneficial or undesirable depending on the application. For example, controlled denaturation can support gel formation, while excessive denaturation can reduce solubility or cause sedimentation in high protein beverages.

The collective behaviour of a powder when mixed with water, including wettability, dispersibility and solubility. Wettability describes how readily the powder becomes penetrated by water, dispersibility how easily it breaks apart and distributes through the liquid, and solubility how completely the dissolved components remain in solution without sediment or insoluble material. In dairy protein powders, these properties are strongly influenced by particle structure, agglomeration, lecithination, protein denaturation, mineral balance and processing conditions.

The study of how a material flows and deforms under applied force. In dairy and protein systems, rheology includes properties such as viscosity, shear-thinning, gel strength and flow behaviour, and is influenced by protein concentration, temperature, pH, minerals, fat and processing history. It is important in beverages, concentrates, yoghurt, desserts and high protein formulations, where it affects processing, pumping, filling, texture and consumer perception.

Visible dark or burnt particles formed when dairy solids are exposed to excessive heat during processing, particularly during evaporation or spray drying. Their presence can indicate product build-up, fouling or overheating on hot surfaces and may affect powder appearance, flavour and product quality. Scorched particle levels are therefore commonly monitored as part of quality control for milk, whey and protein powders.

The characteristics of a food or ingredient perceived through the senses, including taste, aroma, appearance, texture and mouthfeel. In dairy and protein products, sensory properties are influenced by raw material quality, processing conditions, formulation and storage and are critical to product quality and consumer acceptance. Sensory evaluation can range from routine quality checks to structured panel assessment.

The electrical charge at the surface of proteins, fat droplets or other dispersed particles in a dairy system. It influences how strongly particles attract or repel one another and can therefore affect aggregation, emulsion stability, sedimentation and overall physical stability.

A measure of the amount of water in a product that is available to support microbial growth and physical or chemical changes, rather than the total amount of water present. In dairy powders, water activity is an important indicator of shelf life, caking tendency, stickiness and storage stability. Two powders can have similar moisture contents but different water activities, depending on how strongly the water is bound within the product.

A spore-forming bacterium commonly found in the environment and able to survive some heat-processing steps through its spores. In dairy powders, high levels may indicate poor raw-material quality, ineffective hygiene or growth before drying, and certain strains can produce toxins associated with foodborne illness.

A layer of microorganisms that attaches to a surface and becomes embedded in a protective matrix. In dairy processing, biofilms can develop on equipment surfaces, pipework, tanks, drains and difficult-to-clean areas, particularly where residues and moisture remain. They are important because they can protect microorganisms from normal cleaning and sanitising conditions and become a persistent source of post-process contamination, including spoilage organisms and pathogens such as Listeria monocytogenes.

A group of bacteria, primarily associated with Staphylococcus aureus, used as an indicator of contamination from people, equipment or poor handling practices. At sufficiently high levels, some strains can produce heat-stable enterotoxins.

A pathogen of particular importance in powdered infant formula and dry nutritional products. It can survive in low-moisture environments and is associated with severe infections in vulnerable infants, making environmental hygiene and post-drying contamination control especially important.

A family of bacteria commonly used as an indicator of hygiene and post-process contamination. Their presence in dried dairy ingredients can suggest inadequate sanitation, environmental contamination or contamination after the main heat treatment step.

A bacterium commonly used as an indicator of faecal contamination or poor hygiene control. Its detection in dairy ingredients can indicate a breakdown in sanitary conditions or post-process contamination.

A foodborne pathogen capable of persisting in wet processing environments, drains, equipment niches and biofilms. Although it does not grow in dry powder, its presence can indicate poor environmental hygiene and potential post-process contamination.

The number of microorganisms present in a raw material, process stream or finished product. In dairy processing, microbial load is an important indicator of raw material quality, hygiene and process control, and can influence product safety, shelf life and the effectiveness of downstream heat treatment. High microbial loads before concentration or drying can be particularly problematic because microorganisms or their heat-stable enzymes and toxins may persist even when the final powder has a low water activity.

Fungi that can cause spoilage and quality deterioration. Their presence in powders may indicate environmental contamination, moisture ingress or poor storage conditions, and some species can produce mycotoxins under suitable conditions.

A controlled heat treatment used to reduce pathogenic and spoilage microorganisms to a safe and acceptable level while minimising changes to product quality. In dairy processing, pasteurisation is a critical control step for milk, whey and other liquid dairy streams before further processing. Time–temperature conditions must be matched to the product and process objective, as excessive heating can increase protein denaturation, fouling and flavour changes, while insufficient treatment may compromise microbiological safety.

A major foodborne pathogen of particular concern in low-moisture foods and dairy powders because it can survive for long periods in dry environments. Its presence is unacceptable in finished products and requires stringent environmental, hygiene and post-pasteurisation contamination controls.

An overall measure of the number of viable microorganisms present in a product. It is used as a general indicator of microbiological quality, hygiene and process control, rather than as a direct measure of food safety.

Microorganisms associated mainly with spoilage, particularly where moisture or water activity allows growth. In dairy powders, elevated yeast counts can indicate poor hygiene, contamination or inappropriate storage conditions.