Industrial and applied chemistry

Additives, preservatives, flavourings

How food additives alter texture, stability, shelf life and flavour—and how their use is evaluated for safety and function.

1 Lower secondary 2 Upper secondary 3 Undergraduate 4 Advanced 5 Research

IntuitionA small ingredient, a measurable effect

An additive is used for a defined technological purpose: an emulsifier helps oil and water remain dispersed; a preservative slows spoilage; a flavouring supplies or restores aroma. The name alone does not establish safety or benefit—the dose, food matrix, exposure and intended function matter.

SchoolStructure explains function

Molecules with both water-loving and oil-loving regions can gather at an interface. Lecithins and mono-/diglycerides can therefore stabilize droplets in sauces and dressings. Hydrocolloids such as pectin or alginate thicken water phases by forming hydrated networks; performance depends on pH, salts, temperature and concentration.

\Gamma = \frac{n_{ads}}{A} \qquad \text{and} \qquad \gamma = \frac{F}{L}

Here surface excess Γ describes adsorbed material per area, while interfacial tension γ is force per length. Adsorption of a surfactant can lower γ and make droplets easier to form; it does not by itself guarantee long-term emulsion stability.

Example: Choose a stabiliser for a dressing

A dressing separates after storage. First identify whether droplets coalesce, cream upward or sediment. Then test an emulsifier and a thickener separately, controlling oil fraction, pH and temperature; compare droplet size and separation over time.

Solution

An emulsifier targets coalescence at the interface; a thickener can slow droplet motion. A controlled factorial comparison is more informative than increasing both ingredients at once.

UndergraduatePreservation is a hurdle system

Weak-acid preservatives are often most active in their undissociated form, which can cross microbial membranes. Lower pH shifts the balance toward that form, but efficacy is also shaped by water activity, packaging, temperature, the target organism and food composition. Formulation uses multiple hurdles rather than assuming one additive solves every hazard.

f_{HA} = \frac{1}{1+10^{\mathrm{pH}-\mathrm{p}K_a}}

This Henderson–Hasselbalch relation estimates the undissociated fraction of a monoprotic weak acid. It is a speciation estimate, not a direct prediction of microbial kill: partitioning into food phases and organism-specific susceptibility still matter.

Rotate the structure and connect functional groups to polarity and chemical reactivity. Molecular structure helps explain aroma chemistry, but sensory character also depends on concentration and the food matrix.

ResearchResearch frontier

References

Food Chemistry · H.-D. Belitz, W. Grosch, P. Schieberle, 2009
A review of the use of hydrocolloids in food products · S. Saha, S. Bhattacharya, 2010
Food additives · World Health Organization, 2023