The physical, chemical, functional and sensory properties of food in manufacture, including how these properties are exploited and controlled to achieve a safe, consistent and acceptable product

What this dot point is asking

This dot point asks you to understand that food is not just a collection of ingredients but a material with measurable properties that manufacturers must understand and control. You need to describe the physical, chemical, functional and sensory properties of food and, more importantly, explain how manufacturers exploit these properties to create a product that is safe, consistent and acceptable to consumers. Strong answers do more than list properties: they connect a named property to a real manufacturing decision, such as why an emulsifier is added to mayonnaise or why starch thickens a sauce when heated. The focus is on properties as tools the manufacturer manipulates, not as facts to memorise.

Physical properties

Physical properties are the measurable characteristics of food that do not change its chemical makeup, such as size, shape, weight, density, viscosity (thickness of flow) and solubility. Manufacturers control physical properties to keep products consistent and to suit equipment, for example sizing potato pieces so they cook evenly, controlling the viscosity of a sauce so it pumps and pours correctly, and ensuring particle size is uniform so a powder dissolves predictably. Physical properties also affect packaging and portioning, so they matter throughout the production line.

Chemical properties

Chemical properties relate to how food reacts at a molecular level, including its acidity or alkalinity (pH) and its tendency to undergo chemical reactions. Two important reactions are browning reactions. Enzymic browning occurs when cut fruit such as apple is exposed to oxygen, which manufacturers control with acid (lemon juice) or by excluding air. Non-enzymic browning, including the Maillard reaction between sugars and proteins and caramelisation of sugars, gives baked and roasted foods their colour and flavour. pH is also a key safety control, because acidic conditions inhibit many spoilage and pathogenic microorganisms, which is why pickling and fermentation preserve food.

Functional properties

Functional properties are the ways ingredients behave and change during processing, and they are the most important properties for manufacturing. Key functional properties include: emulsification, where an emulsifier such as lecithin in egg yolk allows oil and water to mix in products like mayonnaise; gelatinisation, where starch granules swell and thicken a liquid when heated with water, as in custards and sauces; dextrinisation, the browning of starch under dry heat that crisps and colours toast and pastry; coagulation, where proteins set when heated, as egg sets a quiche or heat firms meat; aeration, where air is trapped to give volume and lightness, as in whipped cream or beaten egg white in a meringue; and crystallisation, controlled in confectionery to produce smooth fudge or grainy toffee. Manufacturers select ingredients and processing conditions specifically to trigger or prevent these behaviours.

Sensory properties

Sensory properties are the characteristics a consumer perceives: appearance and colour (sight), aroma (smell), flavour (taste combined with smell), texture and mouthfeel (touch), and even sound, such as the crunch of a chip. Sensory properties largely determine whether consumers accept and repurchase a product, so manufacturers measure and control them carefully. Sensory properties are assessed through sensory evaluation using trained or consumer panels, and they are closely linked to the physical, chemical and functional properties above, because the colour of a baked good comes from browning reactions and its lightness comes from aeration.

How properties are controlled in manufacture

Manufacturers control properties through ingredient selection, formulation and processing conditions. They add functional ingredients such as emulsifiers, stabilisers, thickeners and raising agents to achieve a desired property; they control temperature, time, mixing and moisture to trigger reactions like gelatinisation or coagulation at the right point; and they monitor pH and water activity to keep products safe and stable. Controlling properties is what makes mass-produced food consistent from batch to batch, which is a key expectation in manufacturing and a clear link to quality management.

Why this matters for the HSC

Examiners reward students who can name a property and immediately apply it to a real product and a manufacturing decision, such as explaining gelatinisation through a custard or emulsification through mayonnaise. They reward correct terminology, especially for functional properties, and an understanding that properties are interconnected and deliberately manipulated. Linking properties to safety (pH, water activity), to sensory acceptance and to consistency shows the integrated understanding that distinguishes a top response.