Quality
Post-harvest quality attributes
A quality attribute is one measurable property of a harvested lot. No single attribute is “quality” — each answers one question, and reading it as an answer to a different question is the most common and most costly post-harvest mistake.
One attribute answers one question
Moisture content tells you whether a lot can be stored safely. It does not tell you whether the lot is safe to eat, what grade it will make, or how it will mill. Test weight is a grading factor with a long history; it is not a measure of protein, soundness, or value on its own. Every entry here therefore names the single question its attribute answers, and states explicitly what it must not be read as.
These are the five questions, and they are genuinely different:
- Quality measurement
- What is this property, physically?
- Commercial grading
- How will the lot be described and priced under a standard?
- Food and feed safety
- Is it safe to eat or feed? A regulatory question, not a quality one.
- Storage stability
- Will it keep, and for how long, under given conditions?
- Processing suitability
- Will it perform in a specific process or end use?
No universal thresholds
Safe and acceptable values are specific to the commodity, the measurement basis, the intended storage duration, the climate, and the applicable standard or contract. AgricultureID publishes no universal thresholds: each entry names the units an attribute is expressed in and points to the standard or national guidance that sets the limits.
See quality measurements for how each attribute is observed, and post-harvest defects for how lots fail.
Quality attributes A–Z
Each entry covers what the property is, the one question it answers, what it is not an indicator of, the units it is expressed in, and how it is measured.
30 entries
- Quality attribute
Broken Kernels
Broken kernels are grain fragments smaller than the size defined by the sieve a grading standard prescribes — a procedural definition, not a natural category. Broken material raises storage risk and reduces milling yield, but the figure does not reveal what caused the breakage and is not comparable between standards with different sieve definitions.
- Quality attribute
Bulk Density
Bulk density is the mass of a bulk of grain or seed per unit volume, including the air between kernels. It is the engineering property behind bin and silo sizing, structural loading, and transport planning, and it is deliberately distinct from test weight, the same underlying quantity measured under a prescribed standard as a commercial grade factor.
- Quality attribute
Chilling Sensitivity
Chilling sensitivity is the susceptibility of many tropical and subtropical commodities to injury from temperatures that are low but still above freezing. Symptoms typically develop only after the commodity has been rewarmed, which is what makes chilling injury a dangerous, easily missed failure in the cold chain.
- Quality attribute
Colour
Colour, measured instrumentally, is a set of coordinates in a defined colour space read under a specified illuminant and observer. It is the attribute consumers rely on most heavily when judging produce, but colour change and eating quality are governed by different mechanisms and are frequently decoupled — colour is not a ripeness verdict.
- Quality attribute
Dockage
Dockage is material readily removable from a grain lot by a prescribed cleaning device — chaff, straw, weed seeds, dust, and other fine material. Unlike most quality factors, its defining feature is procedural: it is determined with specified equipment, reported separately from the grade, and deducted directly from the weight the seller is paid for.
- Quality attribute
Dry Matter Content
Dry matter content (DM) is the proportion of a unit remaining after all water has been removed — the complement of moisture content on a fresh-weight basis, reported the other way round for a different set of questions. It is the accepted harvest-maturity criterion for avocado, a strong predictor of eventual eating quality in mango and kiwifruit, and a governing factor for potato processing quality and cassava starch yield, but a high dry matter figure describes accumulated potential, not the eating quality a fruit already has.
- Quality attribute
Ethylene Production
Ethylene production is the rate at which a commodity releases ethylene, a gaseous plant hormone active at trace concentration. In climacteric fruit, production becomes self-reinforcing at the onset of ripening, and the practical consequence is that heavy producers and ethylene-sensitive commodities cannot safely share a store or a truck.
- Quality attribute
Falling Number
The Hagberg falling number is the time, in seconds, for a stirrer to fall through a heated aqueous flour or meal suspension — an indirect measure of alpha-amylase activity. High enzyme activity thins the starch paste and makes the stirrer fall faster, so a LOW falling number means HIGH enzyme activity, the inverse of what the name suggests.
- Quality attribute
Firmness
Firmness is the resistance of a fruit or vegetable's flesh to deformation or penetration, conventionally reported as the maximum force needed to drive a probe of specified diameter a specified depth into the pared flesh. It is the workhorse ripeness and shelf-life indicator for apples, pears, stone fruit, kiwifruit, and tomatoes, because softening tracks the ripening process more reliably than almost any other single property — but a firmness figure without its probe size, penetration depth, and fruit temperature stated is not a comparable figure.
- Quality attribute
Foreign Material
Foreign material is matter other than the commodity itself — and, in most standards, other than the grain that remains after dockage has already been removed — expressed as a mass percentage. The definition is procedural and standard-specific: what counts as foreign material depends entirely on the standard applied, so a figure from one standard cannot be read against another.
- Quality attribute
Germination Capacity
Germination capacity is the proportion of a seed sample that produces normal seedlings under prescribed test conditions. It is decisive for seed lots and malting barley and irrelevant to grain destined for milling or feed — and it is not the same thing as field emergence or seed vigour.
- Quality attribute
Heat Damage
Heat damage is the proportion of kernels discoloured or darkened by heat, arising either from over-hot artificial drying or from self-heating in store driven by respiration of damp grain, moulds, and insects. It is a defined factor in commodity grade standards, scored against reference samples rather than by unaided judgement.
- Quality attribute
Insect Damage
Insect damage is kernels bored, tunnelled, or fed on by storage insects — a defined factor in grain standards, assessed by examining a drawn sample. Because it records feeding that has already happened, it is a poor guide to whether a lot is infested right now, and it can miss a serious hidden infestation entirely.
- Quality attribute
Internal Quality
Internal quality is the condition of tissue beneath the skin — flesh colour and texture, internal browning, breakdown, cavities, hollow heart, translucency, seed or core condition, granulation, and internal decay. Because external appearance and internal condition are decoupled, internal disorders routinely escape the grading line and reach the buyer.
- Quality attribute
Kernel Hardness
Kernel hardness is the resistance of a kernel and its endosperm to deformation and fracture. In wheat it is largely genetically fixed and expressed as the hard/soft market classification, and it governs milling behaviour — but it is not a measure of protein content, baking quality, or grade, and it is a distinct property from vitreousness.
- Quality attribute
Maturity Index
A maturity index is a commodity-specific standard used to decide whether produce has reached the stage at which it can be harvested and still complete its development to acceptable eating quality. It is computed from separately measured component attributes, and it is not the same question as ripeness.
- Quality attribute
Mechanical Damage
Mechanical damage is physical injury inflicted by harvesting, handling, conveying, and packing — impact bruising, compression, abrasion, cuts, and internal cracking. It spans both grain (cracked kernels, invisible internal fissures) and fresh produce (bruised fruit, skinned tubers), and its central importance is that it breaks the commodity’s primary physical defence and opens an entry route for decay.
- Quality attribute
Moisture Content
Moisture content is the proportion of water in a grain or seed lot, expressed on a wet-basis or dry-basis percentage. It is the primary determinant of how stably a lot can be stored — not a safety verdict, not a grade, and not a predictor of mould growth on its own.
- Quality attribute
Mould Incidence
Mould incidence is the proportion of kernels or units in a sample showing visible mould infection or growth. It is a food- and feed-safety surveillance signal, not a mycotoxin result: visible mould does not confirm toxin, and clean-looking grain is not confirmed toxin-free.
- Quality attribute
Oil Content
Oil content is the proportion of an oilseed lot that is extractable lipid, reference-determined by solvent extraction and estimated routinely by NMR or near-infrared methods. It governs crush yield and lot value, but it says nothing about the extracted oil’s quality or about how well the seed will store.
- Quality attribute
Protein Content
Protein content is the proportion of a grain or seed lot made up of protein, conventionally estimated from a total-nitrogen measurement using a commodity-specific conversion factor. It governs milling, baking, and feed value, but it is a quantity of protein, not a statement about the protein’s functional quality.
- Quality attribute
Respiration Rate
Respiration rate is the rate at which a harvested commodity consumes oxygen and evolves carbon dioxide, releasing heat and using up its own stored reserves. It is essentially the clock on shelf life, and nearly every post-harvest cooling and atmosphere-control practice exists to slow it.
- Quality attribute
Size Uniformity
Size uniformity is the degree to which the units in a lot fall within a stated size class — screened by sieve or screen for grain and seed, and by diameter, mass, or count for fresh produce. Its purpose is commercial and logistical rather than a measure of intrinsic quality, and confusing the two is the most common misreading of a size grade.
- Quality attribute
Soluble Solids Content
Soluble solids content (SSC) is the concentration of dissolved solids in expressed fruit juice, measured by refractive index and conventionally reported in degrees Brix. Because °Brix is calibrated against a pure sucrose solution while real juice also contains organic acids, soluble pectins, amino acids, and minerals alongside sugars, SSC is a proxy that correlates well with sugar content in most fruit rather than a direct sugar assay, and it is not, by itself, a measure of sweetness or of maturity.
- Quality attribute
Starch Content
Starch content is the dominant carbohydrate reserve in cereals, potatoes, and cassava, and it drives ethanol yield, wet-milling yield, feed energy, and — in potato — fry quality and specific gravity. It measures how much starch is present, not how that starch is structured or whether it remains sound.
- Quality attribute
Sugar-Acid Ratio
The sugar-acid ratio is a computed attribute, not a measured one: soluble solids content divided by titratable acidity, each determined separately on the same juice sample. It tracks the flavour balance consumers actually respond to better than either component alone and underpins citrus maturity regulation in several jurisdictions, but as a ratio of two proxies it inherits every limitation of both, and it cannot distinguish a high-sugar/high-acid fruit from a low-sugar/low-acid one that produces the same number.
- Quality attribute
Test Weight
Test weight is the mass of grain that fills a container of defined volume under a standardised filling procedure. It is one of the oldest and most widely used commercial grading factors for cereals, but it is not a measure of milling yield, protein, or intrinsic quality.
- Quality attribute
Thousand Kernel Weight
Thousand kernel weight is the mass of a counted one thousand kernels, adjusted to a stated moisture basis. It is used to calculate seeding rates, estimate potential milling yield, and support yield-component analysis, but it is a property of a specific lot, not a fixed trait of a variety, and it means nothing without its moisture basis stated.
- Quality attribute
Titratable Acidity
Titratable acidity (TA) is the total titratable acid in expressed fruit juice, determined by neutralising the juice with a standard alkali to a defined endpoint and conventionally expressed as the commodity's dominant acid — malic in apples, citric in citrus, tartaric in grapes. That choice of acid is a reporting convention, not a chemical fact about what is present, so a TA figure is meaningless without knowing which acid it was expressed as, and it must not be confused with pH, a related but genuinely different measurement.
- Quality attribute
Water Activity
Water activity is the ratio of the vapour pressure of water in a commodity to that of pure water at the same temperature — a measure of how available the water is, not how much of it there is. It is the property that governs whether storage fungi can grow, and it is temperature-dependent and commodity-specific in a way total moisture content is not.
Sources
This article draws on the following authoritative sources. See our sources & methodology for how they are selected.
- [1]FAO — Food and Agriculture Organization (opens in a new tab)Authoritative
Food and Agriculture Organization of the United Nations (FAO)
Cited for: Post-harvest quality concepts
- Type:
- Intergovernmental organization
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12
- [2]USDA ARS — Agricultural Research Service (opens in a new tab)Authoritative
USDA Agricultural Research Service (ARS)
Cited for: Quality measurement research
- Type:
- Government agency
- Jurisdiction:
- United States
- Accessed:
- 2026-07-12
- [3]AHDB — Agriculture and Horticulture Development Board (opens in a new tab)High
Agriculture and Horticulture Development Board (AHDB)
Cited for: Grain quality and storage guidance
- Type:
- Government agency
- Jurisdiction:
- United Kingdom
- Accessed:
- 2026-07-12