Penetration of a substance (for example a food component) into another material (such as packaging).


An acid has a pH below neutral. Hence, an acid liquid is a liquid of pH<7 and is the opposite of alkaline on the pH spectrum. Foodstuffs of pH<4.6 are often referred to as “high-acid”.

Acid catalysed hydrolysis

A chemical reaction promoted by an acid environment in which a complex molecule is split into two smaller molecules by the addition of water.

Acid content

Total acidity for orange juice is expressed as grams citric acid per litre juice (Europe) or as grams citric acid per 100 g juice, % w/w (US).


Total acid content of juice.


The binding of gases, liquids or dissolved substances by adhesion on the surfaces of solids.

Aerobic reaction

A reaction that requires free oxygen to take place.


The white spongy layer of tissue found just under the coloured outer portion of the peel (flavedo). The albedo layer is rich in pectin substances and hemicellulose.


Being alkaline (or basic) means having a pH above neutral. Hence, an alkaline liquid is a liquid of pH>7 and is the opposite of acid on the pH spectrum.

Anaerobic reaction

A reaction that does not require free oxygen to take place.


A compound that oxidizes readily, thereby preventing or minimising oxidation of other compounds. It can occur naturally or be added to food and drinks.


An odour with a pleasant connotation. For orange juice, the word is also used for the flavour fraction called essence aroma (defined below).

Ascorbic acid

A vitamin found in plants, especially fruits and green vegetables. It forms white crystals when purified and dried. Also called vitamin C.



Weight unit for orange fruit used in reporting of harvest and plant intake. One box (field box) is defined as 90 lb (or 40.8 kg) of oranges. (A box of grapefruit equals only 85 lb of fruit.)

Brix/acid ratio

See ratio.



A class of yellow, orange and red pigments that occurs naturally in fruits and vegetables. Carotenoids have traditionally been classified as carotenes (pure hydrocarbons) and xanthophylls (hydrocarbons containing oxygen).

Cell sacs or whole cells

Intact citrus cells that still contain juice. Whole cells cannot be obtained by conventional juice extraction methods because these break open cells to remove the juice.


A commercial expression sometimes used for pulp. Is also referred to as frozen cells and frozen pulp.


Cloud gives rise to the opaque appearance of orange juice. It is formed by soluble and insoluble compounds released during juice extraction. The solid particles are kept in suspension by the presence of soluble pectin in the juice. Cloud is an important quality attribute of most citrus juices and contributes to mouthfeel.

Cloud loss

The undesirable occurrence of orange juice separating into a clear upper phase (serum) and a bottom sediment. Cloud loss occurs when juice viscosity is reduced by a too low concentration of soluble pectin (in turn the result of enzyme activity). Hence, insoluble compounds can no longer be maintained in suspension.

Cold-pressed oil

See cold-pressed peel oil.

Cold-pressed peel oil

The oil derived from the peel of citrus fruits. Oil sacs found in the surface of the peel are ruptured during oil extraction. The oil is recovered from the oil/water emulsion by mechanical means (as opposed to thermal processing). Also known simply as cold-pressed oil, peel oil or CPPO.

Colour score

A numerical value to rate the colour of citrus juices. In the US it is often determined by the use of a Hunter citrus colorimeter. A “score” is assigned by comparing the red and yellow colour components of the sample to a USDA standard.

Core wash

The process of recovering soluble solids (mainly sugars) from the central core of the fruit discharged separately from squeezer-type extractors. The resulting liquid product is also called core wash. See also the analogous pulp wash.

Corrected °Brix

°Brix value obtained after correction for the acid content of juice. It represents the actual sugar concentration of juice.


The degree of crystallinity is the concentration of well-organized molecular area in a solid material. The higher the crystallinity, the more difficult it is for small molecules like oxygen to penetrate.



The main component of oil found in oranges. d-Limonene makes up >90 % of peel oil and essence oil. It is also recovered as a by-product from waste peel. d-Limonene belongs to a group of hydrocarbon molecules called terpenes.



The process of removing air (oxygen) from juice. Dispersed air as free air bubbles is quite easily removed from juice but dissolved air requires an effective deaeration process.


The equipment in which juice is deaerated, typically a system featuring a vacuum vessel.


Factors that degrade citrus product quality. Examples of defects are the presence of small seeds or black specs in juice, poor colour scores and out-of-range ratios.


Diacetyl is a natural fermentation by-product of acid-forming bacteria and imparts a “buttermilk” odour if its concentration exceeds 1.0 ppm.


The mass transport of substances (such as oxygen and limonene) through material (for example polymer). The driving force is the difference in concentration of the substance in question on the inside and outside of a material. The substance will flow from an area of higher concentration to an area of lower concentration.


The ability of a substance to permit diffusion.



Another name for the edible portion of the orange fruit.

Enzyme activity

A measure of enzyme concentration in juice. The necessary inactivation of enzymes is achieved by heat treatment of juice.


These are proteins that catalyze biochemical reactions. As regards orange juice quality, pectin methyl esterase (PME) is the most important enzyme in the juice as it is responsible for breaking down pectin, thereby causing cloud loss. It is found in cell walls (for example peel and juice sacs) and is squeezed out from the fruit and mixes with the juice during the extraction process.


The volatile components recovered from the evaporation process. Essence is separated into an aqueous phase (essence aroma) and an oil phase (essence oil).

Essence aroma

A fraction of volatile flavours recovered from the evaporation process together with essence oil (in a ratio of about 10:1). Essence aroma is clear and colourless and contains water-soluble flavour components originating from the juice. It contributes a fruity aroma and a light citrus taste to juice. Also known simply as aroma or water phase.

Essence oil

This is a clear, pale yellow oil recovered from the evaporation process. Essence oil is a source of specific flavour notes, mainly esters and carbonyls. It contributes a floral fruity aroma and a juicy flavour to juice.

Essential oils

A general term for volatile oils, extracted from plants, fruits and flowers, having characteristic odours.


The process of removing water from juice by heat.


Extraction related to oranges is the process of squeezing out juice from either whole or halved oranges by means of mechanical pressure. Peel oil is also obtained by a mechanical extraction process.



Abbreviation for Frozen Concentrated Orange Juice. It is the most common bulk orange juice product stored and shipped. FCOJ is produced commercially by concentrating juice up to 66 °Brix by evaporation.


The original definition of dietary fibres (Hipsky, 1953) is materials derived from plant cell walls in foods. It is sometimes used to mean large solid particles in juice, better described as floating pulp.


Equipment used to separate pulp from juice. The process is known as juice finishing.

Flash pasteurization

The expression used for pasteurization carried out in a heat exchanger (during a very short period of time, a “flash”) as opposed to tunnel pasteurization. There is no flash of product. Also referred to as high temperature short time heat treatment (HTST).


The coloured outer portion of peel. Carotenoids in the flavedo impart the characteristic colour of orange fruit. The flavedo also includes the oil glands, which contain peel oil


A complex combination of the sensations experienced through the senses of taste and smell, as well as the textural sensations perceived via the mouth or throat.


The word used to express the concentration factor of flavours in a liquid. For example, in a 5-fold flavour, the flavour compounds have been concentrated five times.



The tendency of concentrate to become lumpy and difficult to reconstitute is known as gelation. It results from enzyme activity caused typically by insufficient pasteurization prior to juice concentration, or from incorrect storage temperature.



A flavonoid found in citrus juices. As it is highly insoluble, it precipitates during juice concentration and accumulates on surfaces in evaporators and extractors. Although it imparts no off-flavour to juice, it may appear as white specks and be considered a defect.

Hot filling

The filling procedure whereby the high temperature of the product being filled is used to “sterilize” the food-contact surface of the packaging material

Hydrogen peroxide

A chemical with the formula H<sub>2</sub>O<sub>2</sub>. It is a clear liquid with strong oxidative power and is produced as aqueous solutions of 35-90% w/w hydrogen peroxide concentration. It is used as a sterilization agent in filling machines.


An instrument placed in a liquid for measuring its relative density or °Brix. It consists of a sealed graduated tube with a weighted bulb at the lower end.


Inert gas

A chemically inactive gas (for example nitrogen).


Juice vesicles

Another name for the juice-containing sacs in orange fruit.



A complex compound that causes bitterness in juice. It is formed in orange juice shortly after extraction. In most juices, the limonin concentration is very low and does not cause a problem except for juice made from Shamouti and Navel (seedless) oranges.


Maillard reaction

A non-enzymatic chemical reaction involving condensation of an amino group and a reducing group (sugars), resulting in the formation of intermediates, which ultimately polymerize to form brown pigments (melanoidins).


A group of orange fruit, Citrus reticulata, that also includes tangerine varieties.


The unit used for screen sizing. Mesh is the number of equal openings per linear inch. A 20-mesh screen therefore has much larger openings than a 60-mesh screen.



A bitterness substance (flavonoid) mainly found in grapefruit juices.


Abbreviation for not-from-concentrate juice. Juice of natural (single) strength that has undergone neither concentration nor dilution during production.


Oil content

The oil content of orange juice is often equated to the concentration of d-limonene as it makes up 90% or more of peel oil and essence oil. d-Limonene can be measured by a relatively simple titration method, the Scott method. Oil content, also referred to as Scott oil, is expressed as % v/v in single-strength juice.


Relating to a property of food that can be perceived by the sense organs.



A type of polysaccharide found mainly in the albedo but also in other parts of the fruit. It is a naturally occurring colloidal stabilizer that gives juice its “body” or viscosity.

Peel oil

See cold-pressed peel oil.


It is a measure of a material’s ability to be penetrated, particularly by gases. The permeability value is obtained by multiplying diffusivity and solubility.


Measures undertaken on plants to protect human, animal and plant health.

Plate count

A method of determining the number of microorganisms in food. It is often expressed as colony-forming units per millilitre sample (CFU/ml).


Abbreviation for pasteurized orange juice. It is a term used in Florida for NFC juice.

Polar (and non-polar)

A polar molecule such as water has both positively and negatively charged regions. Two polar molecules intermix as they are attracted by each other’s dipole forces. A non-polar molecule, such as oil, has no areas of positive and negative charge within it. Generally, non-polar molecules do not intermix well with polar ones.


A large molecule that is obtained by polymerization of many smaller identical molecules (monomers). In this document, polymer is used synonymously with plastic.


Polymers prepared by polymerization of α-olefins.Examples
of polyolefines are polyethylene and polypropylene.

Pounds juice per box

The actual weight of juice extracted from a 90 lb box of orange fruit as measured by the State Test extractor (Florida).

Pounds solids per box

A measure in weight of the total dissolved solids in a given box of fruit. Used in Florida as basis for payment of fruit. It is calculated by multiplying the amount of juice per box (by the State Test) with the Brix level of the juice.

Press liquor

A product stream in the feed mill area obtained by removing moisture from the citrus peel in a (screw) press. The press liquor is concentrated in a waste heat evaporator to form molasses.


The solid particles in orange juice. Also the commercial name for the product (consisting of broken pieces of cell sacs and segment walls) that is added back to the final juice. Several terms are used to define pulp in juice. They include:

Floating pulp – larger solid particles in juice consisting of pieces of ruptured cell sac and segment wall. Most float to the top after juice is stirred.

Sinking pulp – very small solid particles (<0.5 mm) which are suspended in the juice and settle from the juice with time or spin down in a centrifuge. Typical values range from 5 to 12 v/v centrifuged pulp.
Suspended pulp, bottom pulp and centrifuged pulp are sometimes used as synonyms for sinking pulp.

For pulp as a product:
Aseptic pulp – pulp product stored in aseptic bag-in-drums.
Frozen pulp – pulp product sold in frozen form.

Pulp wash

The process by which soluble solids (mainly sugars) are recovered from pulp. The soluble solids are leached from the pulp with water through a system of mixing screws and finishers. The liquid stream from a pulp wash system is referred to as pulp wash, secondary solids or water extracted soluble orange solids (WESOS).


Quick Fibre

A test method to determine the relative dryness of pulp. It indicates how hard the squeezing of pulp to remove juice in the finishers has been. Quick Fibre (QF) is also a measure of how wet t he pulp is as it exits the final, or drying, finisher in the pulp production line.



The ratio is obtained by dividing the °Brix of a juice product by the acid content (as % wt). The ratio, also referred to as Brix/acid ratio, is important for describing taste as a measure of the balance between sweet and sour sensations. Consumers prefer a ratio of around 15:1.


Contamination of juice with microorganisms after it has been pasteurized. Also known as reinfection.

Refractive index

A measure of how much light is refracted –changes direction – on passing from one medium to another. The refractive index for a solution depends on its concentration. The measured refractive index can be translated into concentration of soluble solids of a solution such as orange juice.


An instrument for measuring refractive index.


Sensory analysis

Examination of a product by the sense organs.

Shelf life

The time period up to the point when a food product becomes unacceptable from a safety, sensorial or nutritional perspective.


The term assigned to juice at its natural strength, either directly from the extraction process or in a reconstituted form.


Insoluble solids are, simply put, solids that will not dissolve in the liquid in question. In orange juice they consist mainly of cellulosic and insoluble pectic substances generally associated with pulp.

Soluble solids are solid materials that will dissolve in the liquid in question. Sugars and acids in citrus juices are commonly referred to as soluble solids.

Specific gravity

Refers to the actual weight of a liquid in relation to water (at defined temperatures). Also called relative density.

State Test

Standardized method used in Florida to establish the potential juice yield from a delivered load of fruit. Juice extraction is carried out using a State Test extractor under well-defined operating conditions. The actual juice yield during commercial processing of the same fruit batch is different to, and often higher than, the State Test yield.

Sweet oranges

For orange juice, the sweet orange, Citrus sinensis, is the most important group of orange fruit. EU regulations stipulate that orange juice may only be made from the sweet orange, whereas in other markets legislation allows the addition of small amounts of juice from other orange varieties, like mandarins, to balance juice taste.



Sensations perceived via the taste buds of the tongue when stimulated by certain substances.



Viscosity is a measure of the “thickness” of a fluid. It affects the “body” of the juice created primarily by pectin-related stabilization of the cloud or colloids in the juice. The presence of insoluble material also contributes to increased juice body or viscosity.


Washed pulp

The solid particles remaining from the pulp wash process. It is sold in frozen form for addition to fruit beverages, or recovered in the feed mill area for use as animal feed.



Concentration of all soluble solids in juice. It is not a measure of sugars only, though sugars make up the bulk of the solids in orange juice. Brix is determined by measuring juice density or refractive index.