Raw Materials and Ingredient Science
The exam tests whether you can predict how an ingredient behaves in a formula: crystallisation, viscosity, sweetness, setting, colour and shelf life. Expect items on sugars, hydrocolloids, fats, milk ingredients, emulsifiers and cocoa components.
Core rules
- Glucose syrup is specified by dextrose equivalent (DE). Higher DE = more reducing sugars, more sweetness, lower viscosity, greater hygroscopicity, faster Maillard browning and greater risk of stickiness. Lower DE = higher viscosity, stronger anti-crystallising effect.
- Invert sugar is formed by acid or invertase hydrolysis of sucrose; it is strongly hygroscopic, so the level is capped in hard candy.
- Hydrocolloids: gelatin is specified by Bloom (gel strength) and viscosity; high-methoxyl pectin needs sugar and acid (pH ~3.0–3.5) to set; low-methoxyl pectin sets with calcium; agar sets hot and gives brittle texture; modified starches need cooking and cooling to develop body.
- Fats: cocoa butter is polymorphic with form V the target; lauric cocoa butter substitutes are incompatible with cocoa butter; hydrogenated fats raise trans/saturated concerns.
- Emulsifiers: lecithin lowers yield value and plastic viscosity; above roughly 0.5 % in chocolate it can raise viscosity and cause off-flavour. PGPR lowers yield value strongly.
- Milk: sweetened condensed milk contributes sugar solids; milk powder contributes protein that drives Maillard browning and caramel flavour.
Worked example
A hard-candy formula is switched from 42 DE to 63 DE glucose syrup at the same solids level. Reasoning: the higher-DE syrup gives a less viscous cook, so the batch flows better and deposits cleanly, but hygroscopicity rises - the sweets will pick up moisture and stick in the wrapper. The higher reducing-sugar content also darkens the colour. Compensate by lowering the syrup's share of total solids, trimming acid, and re-checking moisture and stickiness after 4 weeks of storage.
Traps
- Reading DE as a sweetness measure only.
- Assuming all gelatin grades are interchangeable.
- Over-dosing lecithin to reduce viscosity.
- Ignoring the water and solids contributed by syrups and condensed milk.