lactose definition

L A C T O S E P R O D U C T S D E F I N I T I O N ,C O M P O S I T I O N , F U N C T I O N S 5

R e f e r e n c e M a n u a l f o r U . S . W h e y a n d L a c t o s e P r o d u c t s 41

Typical microbiological analysis

Standard Plate Count <50,000/g

Coliform count 100/g (maximum)

E. coli Negative

Listeria Negative

Salmonella Negative/750g

Coagulase-positive Staphylococci Negative

Other characteristics

Appearance Crystalline,free-flowing powder

Color Light yellow

Flavor Slightly sweet

Solution Slightly turbid, slightyellow, slight whey aroma

5 L A C T O S E P R O D U C T S D E F I N I T I O N , C O M P O S I T I O N , F U N C T I O N S

OVERVIEW

Lactose is, by weight, the most abundant ofthe milk solids. Lactose is a disaccharide composed of the monosaccarides Alpha-D-glucose and Beta-D-galactose. It is a reducingsugar that can, in some circumstances, reactfreely with amino groups in proteins. Lactoseis a useful source of dietary energy and itplays a role in calcium absorption. Severaltypes and grades of lactose products exist, tomeet the needs of various end-users. The U.S.dairy industry also can formulate custom andspecialty products and blends. Please consultyour supplier for additional information.

42 R e f e r e n c e M a n u a l f o r U . S . W h e y a n d L a c t o s e P r o d u c t s

5.1 INDUSTRIAL GRADELACTOSE PRODUCTS

Product DefinitionIndustrial grade lactose products describe a range of lactose products used in feed, fermentation and technical applications. Feedgrade lactose is produced from deproteinizedwhey that is evaporated, crystallized anddried. The finished dry product containsmore than 98% (w/w) lactose.

Lactose (minimum)** 98%***

Protein 0.5–1.0%

Fat 0.1%

Ash 0.1%–0.5%

Total Moisture** 4.5–5.5%

*Please consult your U.S. supplier for detailed product specifications.

**Includes bound water (includes all forms such as monohydrate).

***Includes all forms such as monohydrate.

Typical Composition*

Physical and Chemical Aspects*

R e f e r e n c e M a n u a l f o r U . S . W h e y a n d L a c t o s e P r o d u c t s


5.2 FOOD GRADELACTOSE PRODUCTS

Product DefinitionFood grade lactose is produced by concentrating whey or permeate (a co-product of whey protein concentrateproduction) to supersaturate the lactose,then removing and drying the lactose crystals. Special processes of crystallization,as well as grinding and fractionated sifting,produce types of lactose which differ in particle size distribution. Today, the industryoffers several types of lactose ranging from superfine to extra coarse crystals for all applications.

According to the U.S. Code of Federal Regulations (21CFR168.122), lactose is thecarbohydrate normally obtained from whey. It may be anhydrous or contain one moleculeof water of crystallization or be a mixture ofboth forms.

The lactose content is not less than 98%, withthe sulfated ash content not more than 0.3%,both on a dry basis. The pH of a10% solutionis not less than 4.5 or more than 7.5.

Figure 5.2Processing of Lactose

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Lactose (minimum)** 99.0%***

Protein 0.1%

Fat 0%

Ash 0.1%–0.3%

Total Moisture** 4.5–5.5%


**Includes bound water.

***Includes monohydrate or anhydrous.


Standard Plate Count 5–15,000/g

Coliform count <10/g

E. coli Negative

Listeria Negative

Salmonella Negative



Scorched particle content 7.5mg/25g(maximum)

Bulk density, tapped 0.7–0.9g/ml(depends upon mesh

size specification)

Appearance Crystalline, free-flowing powder

Color White to pale yellow


Solution Clear, colorless to slightly yellowish, odorless

Typical Composition* Physical and Chemical Characteristics*

Crude Edible NationalComponent Fermentation Grade Grade Formulary

Lactose 98.0 98.4 99.0 99.8

Non-hydrate moisture 0.35 0.30 0.50 0.10

Protein 1.00 0.80 0.10 0.01

Ash 0.45 0.40 0.20 0.03

Fat 0.20 0.10 0.10 0.00

Acidity as lactic acid † † <2 <1

†Not typically determined.Source: Morrissey, P.A. (1985).

Typical Composition of Lactose Products*

Refine and Dry

Concentration

Crystallization

Centrifugation


Functions and Benefits of Lactosein Food Grade ProductsNaturalAll natural “clean” label appeal.

SweetnessLactose is about 25% of the sweetness ofsucrose. The benefits of lactose include:• A clean sweet taste without after-taste.• Increased solids content, viscosity and

improved textural qualities without makingthe product too sweet.

• Providing an energy source in infant formulas, where too much sweetness is undesirable.

Synergistic effects of lactose with other foodingredients may include either sweetnessenhancement or sweetness suppression.Examples of benefits include:• Masking of the bitter after-taste of

saccharine by lactose.• Prolonging the duration of xylitol

sweetness by lactose in chewing gum.

SolubilityLactose is less soluble than sucrose, fructoseand dextrose. The relative solubility of lactose(25°C) is about 30% that of sucrose. Althoughthe relatively low solubility of lactose canlimit its use in certain applications, the lowersolubility can be an advantage in many applications, such as instantized productsand microwaveable products. An example of such a benefit is because of its lower solubility lactose tends to crystallize to agglomerate thereby improving the dispersibility of certain products.


CrystallizationLactose alters the crystallization behavior of other sugars, and is largely used to controlcrystallization in food formulations. With the addition of lactose, both lactose andsucrose crystals become smaller, and the tendency of sucrose crystals to combinetogether is reduced, thereby avoiding sandiness and yielding a softer and smoother crystalline mass.

BrowningLactose can be used in food formulations to provide a desirable brown color. Heatinglactose causes caramelization and/or Maillardreactions which produces brown colors. Lactose, as a reducing sugar, promotes controlled browning in foods by reacting with proteins, peptides and amino acids toform compounds which are highly flavoredand golden brown in color.• Caramelization occurs at high

temperatures. When heated to150°C-160°C, lactose turns yellow, then brown at175°C. This property is beneficial in the production of caramel-type confections.

• Maillard reactions occur at lower temperatures. Lactose is very important in inducing controlled browning in bakedgoods, meat and sausage products, confectionery items and microwaveablefoods. For example, in specialty breads,lactose produces a golden brown crustcolor that does not discolor or fade during storage.

Fermentation and Rheological PropertiesLactose has an exceptional position compared to sucrose and sugar replacers,because of its functionality. Because lactose is not fermented by baker’s yeast (Saccharomyces cerevisiae) it remains available for Maillard and other reactions.Benefits include:• Increased crust browning for enhanced

color and flavor, and improved appearancein baking processes.

• Increased dough and pastry yields, and volume.

• Decreased fermentation tone andimproved fermentation performance in baking.

• Leveling up inferior flour quality.

Lactose can enhance creaming of shorteningand can be added at higher levels thansucrose or dextrose, without causing excessive sweetness. Benefits include:• Fat reduction possible in cakes

and pastries.• Reduced sweetness in cakes possible.

Lactose is not fermented by brewer’s yeast.Benefits can include:• Increased viscosity, improved mouth-feel

and flavor in beer production.

Moisture AbsorptionCrystalline lactose absorbs very little moisture at high humidity compared to other sugars. The non-hygroscopic and freeflow nature of Alpha-lactose monohydrate makes it an ideal dispersing agent for powdered foods.



Flavor, Aroma, and Color Absorption andRetention without Excessive SweetnessLactose is much more effective in bindingand retaining flavor and aroma compoundsthan other sugars. This function enables areduction in added flavors, resulting in possible cost savings. Lactose also absorbsand enhances the color compounds veryeffectively. The benefits of lactose:• Provides a method of adequate dispersion

and slow release of roasted coffee flavor.• Masks off-tastes, and carries flavors

and aromas in spices, seasonings and dry blends.

• Preserves red colors in sauces and ketchup.

Typical ApplicationsFor bakery, confectionery, snack, frozendesserts, diabetic, dietetic, infant formula,baby foods, jams and preserves, sweeteners,instantized powders, meat products, savorymixes, soups and sauces, beer production,nutraceuticals and other foods as:• A “modifier” in humanized infant

formula to correct the balance betweencarbohydrate and protein in breast milkreplacers based on cows’ milk.

• A carbohydrate source for fermentation by selected starter cultures to produce lactic acid for preservation in dry sausagetypes, such as salami.

• An aid in masking off-flavors and after-tastes caused by emulsifying salts,phosphates, and other bitter compoundsin the meat and sausage industry.

• A carrier of flavorings, aroma compounds,coloring agents and artificial sweeteners inconfectioneries, baked goods, spices, andtabletop sweeteners.

• An additive to improve the free-flowingproperties of powdered foods such asinstantized spray dried milk powder.

• An encapsulating agent for volatile flavoring compounds or milkfat or other fats.

• A flavor and color-enhancer in salad dressings, mayonnaise, soups, sauces,baked goods and in fermentationprocesses.

• A crystallization behavior “modifier” of the other sugars to improve body, texture,chewiness and shelf-life of confectioneriessuch as chocolates, fondants, caramels,fudges, sweetened condensed milk andcandy coating processes.

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Standard Plate Count <100/g

E. coli Negative

Salmonella Negative


Penicillin residues Negative

Pesticide residues Negative


Acidity or alkalinity 0.1ml of 0.1N NaOH

Clarity and color: 10% 1cm at 400nm 0.01

Heavy metals <5.0ppm

Loss on drying 0.3%

Protein and light absorbing impurities:

At 210–220nm 0.06

At 210–300nm 0.02

Residue on ignition 0.1%

Specific rotation +54.4˚ to +55.9˚

Bulk density, tapped 0.70–0.90g/ml (depends upon mesh

size specification)

Appearance Pure white, crystalline, free-flowing powder

Solution Clear, colorless, odorless



5.3 PHARMACEUTICAL GRADE LACTOSE

Product DefinitionPharmaceutical grade lactose is produced by concentrating whey or permeate (a co-product of whey protein concentrateproduction) to oversaturate the lactose, then removing, refining, drying and millingthe lactose crystals.

Pharmaceutical grade lactose is produced tomeet rigid specifications such as, specificform and size distribution—monohydrate,crystalline, 40 mesh to 325 mesh, and aspray-dried mixture of crystalline and amorphous lactose for all applications. All products meet the requirements of theU.S., European, and Japanese Pharmacopeia.


Lactose (minimum) 99.8%

Protein 0.01%

Fat 0%

Ash 0.03%

Moisture 4.5-5.5%

Typical Composition*

Physical and Chemical Characteristics*

Figure 5.3.1Processing of Pharmaceutical Lactose

Dissolve and Filter

Concentration

Crystallization

Refine and Dry




Defining Pharmaceutical Grade Lactose

By HARRY G. BRITTAINCenter for Pharmaceutical Physics, Milford, NJ

Copy courtesy: Foremost Farms USABaraboo, WI

Lactose has an empirical formula ofC12H22O11, and a molecular weight of 342.30 Daltons. A variety of experimentshave established its structure as 4-O-(Beta-D-galactopyranosyl)-D-glucopyranose (Figure 5.3.2).

Lactose is obtained from milk in crystallineform by evaporation of the whey remainingafter removal of the fat and precipitation of the casein. It is less sweet than sucrose, and is also less soluble in water than eithersucrose or glucose.

Types of LactoseLactose can be obtained in either a hydrated(specifically as a monohydrate) or anhydrousform. The monohydrate form is obtained bycrystallization out of water solution aroundambient temperature, while the anhydrousform is produced by crystallization at temperatures exceeding 93°C, e.g., spray drying. The monohydrate form will not evolve its water when dried under ordinaryconditions. The two forms exhibit differentcrystal shapes (Figures 5.3.3 and 5.3.4).

Lactose may also be spray dried, to yield a widely used and free flowing form that consists largely of the monohydrate form(depends of drying conditions). This substance also exhibits a characteristic particle shape (Figure 5.3.5).

Uses of Lactose in Pharmaceutical ProductsLactose displays little or no reactivity withmost drugs, and generally displays an acceptable degree of stability. For lactose to be pharmaceutically acceptable (i.e., NF grade), lactose must be demonstrated to be free of protein. The substance is available in a wide variety of particle size distributions, the coarsest of which exhibitexcellent degrees of flowability, as do thespray-dried modifications.

Most typically, regular lactose monohydrateis used as a diluent in tablets that have been manufactured by the wet granulationprocess. The spray-dried monohydrate formand the anhydrous form are usually employedin formulations that are to be dry granulatedand directly compressed. The spray-driedmodification is also widely used as a fillingagent in capsule formulations.

The various types of lactose exhibit superiorphysical properties that have enabled itswidespread use in the pharmaceutical industry. The most important of theseinclude the following:• Lactose is derived from natural sources,

has only a moderately sweet taste.• Lactose is readily obtained in a chemically

pure form, which is cost-effective withother excipients.

• Lactose is, for the most part, both chemically and physically non-reactivewith most drug substances.

• Lactose is available in a variety of naturaland modified forms, each of which exhibitsadvantageous and characteristic physicalproperties (i.e., flowability, particle size,compactability, and stability).

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Figure 5.3.2Empirical Formula of Lactose

H

H HH

H

H

OH

OH

OH

CH2OH

HH

H

HO

OH

CH2OH

Figure 5.3.5Lactose Spray Dried

Figure 5.3.4Lactose Anhydrate (Anhydrous Lactose)

Figure 5.3.3Lactose Monohydrate



Test Procedures Defining Pharmaceutical Grade Lactose

Test Method Lactose Monohydrate Lactose Anhydrate

Clarity and color A solution of 1g in 10ml of boiling water A solution of 1g in 10ml of boiling water of solution is clear and nearly colorless. is clear and nearly colorless.

Specific rotation Dissolve 10g by heating in 80ml of water at 50°C. Dissolve 10g by heating in 80ml of water at 50°C. Allow to cool, and add 0.2ml of 6N NH4OH. Allow to cool, and add 0.2ml of 6N NH4OH. Allow to stand for 30 minutes, and dilute with Allow to stand for 30 minutes, and dilute with water to 100ml. The specific rotation at 20°C is water to 100ml. The specific rotation at 20°C is +54.4°–+55.9.° +54.4°–+55.9.°

Acidity or Dissolve 6g by heating in 25ml of carbon dioxide-free Dissolve 6g by heating in 25ml of carbon dioxide-free alkalinity water, cool, and add 0.3ml of phenolphthalein test water, cool, and add 0.3ml of phenolphthalein test

solution. The solution is colorless, and not more solution. The solution is colorless, and not more than 0.4ml of 0.1 N NaOH is required to produce than 0.4ml of 0.1 N NaOH is required to produce a red color. a red color.

Loss on drying Dry the sample at 80°C for 2 hours. The regular Dry the sample at 80°C for 2 hours.It loses monohydrate form loses not more than 0.5% not more than 0.5% of its weight.of its weight, and the modified monohydrate form loses not more than 1.0% of its weight.

Residue on When a sample is ignited at a temperature of When a sample is ignited at a temperature of ignition 600 ± 25°C, not more than 0.1% remains. 600 ± 25°C, not more than 0.1% remains.

Water content Between 4.5% and 5.5%, when determined using Not more than 1.0%, when determined using Karl Fischer titration on a sample dissolved in Karl Fischer titration on a sample dissolved in 2:1 methanol/formamide. 2:1 methanol/formamide.

Heavy metals Dissolve 4g of sample in 20ml of warm water, add Dissolve 4g of sample in 20ml of warm water, add1ml of 0.1 N hydrochloric acid, and dilute with water 1ml of 0.1 N hydrochloric acid, and dilute with water to 25ml. The metals are precipitated with sulfide, to 25ml. The metals are precipitated with sulfide, and the sample compared to a suitable reference. and the sample compared to a suitable reference. The limit is 5µg/g. The limit is 5µg/g.

Microbial limits The total aerobic microbial count does not exceed The total aerobic microbial count does not exceed100/g, the total combined molds and yeasts count 100/g, the total combined molds and yeasts count does not exceed 50/g, and it meets the requirements does not exceed 50/g, and it meets the requirements of the test for absence of Escherichia coli. of the test for absence of Escherichia coli.

Content of Not applicable. The relative anomeric amounts are determined using alpha and gas chromatography after the test sample has been beta anomers derivatized using a silylation reagent.

Protein and Measure the light absorption of a 1% (w/v) solution in Measure the light absorption of a 1% (w/v) solution in light absorbing the range of 210 to 300nm. The absorbency divided the range of 210 to 300nm. The absorbency divided impurities by the path length (in centimeters) is not more than by the path length (in centimeters) is not more than

0.25 within 210 to 220nm, and not more than 0.07 0.25 within 210 to 220nm, and not more than 0.07 within 270 to 300nm. within 270 to 300nm.

Labeling Where the labeling states the particle size distribution, Where the labeling states the particle size distribution, it also indicates the d10, d50, and d90 values and it also indicates the d10, d50, and d90 values and the range for each. Modified Lactose Monohydrate the range for each.is also labeled to indicate the method of modification.

In addition to its use as a filler and diluent intablets and capsules, lactose has also foundan important role as the carrier of choice for delivery of drug substances throughinhalation. After being coated onto respirablegrade lactose, drug substances may be delivered through dry powder inhalation torelatively deep locations in the lower airwaysof the lung. Here an optimization of particlesize is most important, and it has been established that the use of either too large

or too small particles is detrimental. Themorphology of the carrier lactose particlesalso affects the efficiency of delivery. As aresult, respirable lactose has been developedinto a high-technology excipient, and itsrange of application is predicted to greatlyincrease in the future.

lactose definition

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