Brix (°Bx)

Detailed Explanation

In confectionery, Brix (°Bx) is the common language of recipe and process control. By definition it expresses the sucrose-equivalent total dissolved solids percentage in 100 g of solution. In practice not only sucrose but also glucose syrup, fructose, dextrose, sorbitol, and other soluble solids contribute to the Brix reading.

Measurement methods: • Refractometer — refractive index → Brix conversion; handheld field tool or inline sensor • Hydrometer — specific gravity → Brix conversion; low accuracy, used for quick checks • Density meter (inline measurement instrument type) — high accuracy (±0.02 °Bx), laboratory standard • Polarimeter — for pure sucrose solutions

Typical Brix bands: • Syrup: 65–80 °Bx • Jam/marmalade: 65–70 °Bx • Hard candy (drops): 96–98 °Bx • Jelly/jellybean mass: 78–82 °Bx (at mogul depositing stage) • Marshmallow: 75–78 °Bx • Fondant: 88–92 °Bx

Brix has a direct inverse correlation with water activity (aw); this relationship underlies storage stability and microbiological safety in confectionery.

Why It Matters

Brix is critical in confectionery production for four primary reasons:

1. Cooking end-point — water evaporation during cooking raises the dissolved solids ratio; cooking must stop once the target Brix is reached. Under-cooking = low viscosity + weak gel structure; over-cooking = colour darkening, Maillard by-products, hard texture. 2. Microbiological safety — high Brix → low aw → suppression of mould, yeast, and bacterial growth. Below 65 °Bx, jam shows HMF (hydroxymethylfurfural) growth and microbiological risk. 3. Rheological behaviour — depositors/fillers operate within a tight viscosity window. A jelly mogul depositing line targets 80 ± 1 °Bx; deviation causes filling errors. 4. Shelf life — Brix is directly linked to Equilibrium Relative Humidity (ERH); when storage RH > ERH the product picks up moisture (cap, tack), and otherwise it dries. For 80 °Bx jelly, ERH ≈ 75%; storage should be at 50% RH.

In mogul processes, Brix deviation upsets starch moisture balance: lower Brix → wetter mass → starch absorbs excess moisture → tray bed becomes tacky → shape distorts. So Brix control is a precondition not only for the cooking station but for entire line yield.

Brix–aw–ERH Relationship

Approximate aw equation for a sucrose solution (Norrish model):

ln(aw) = -K × x²

x: mole fraction of dissolved solids (for sucrose x = nsuk / (nsuk + nwater)) K: Norrish constant (6.47 for sucrose)

ERH (%) = aw × 100

Practical conversions (sucrose solution, 25°C): • 60 °Bx → aw 0.86 → ERH 86% • 70 °Bx → aw 0.77 → ERH 77% • 75 °Bx → aw 0.73 → ERH 73% • 80 °Bx → aw 0.68 → ERH 68% • 85 °Bx → aw 0.62 → ERH 62% • 90 °Bx → aw 0.55 → ERH 55%

In the presence of glucose syrup, values shift by 3–8% (molecular-weight correction).

Storage design criterion: RHambient = ERHproduct − safety margin (typically 10–15%)

Engineering Note

Field engineering notes for Brix management:

• Temperature correction — refractometers are calibrated at 20°C; ATC (automatic temperature compensation) is required for hot syrup readings. A raw 78 °Bx read at 80°C may actually be 80 °Bx. • Inline measurement — an inline refractometer at the cooker outlet feeds Brix into a PID loop; cook time / steam flow are auto-adjusted. • Blend balance — the glucose-syrup-to-sucrose ratio determines graining risk; typical jelly recipes use 30–40% glucose syrup to prevent saturation. • Process water management — high-mineral source water shifts refractometer readings; pre-treatment (demineralised or reverse osmosis) is recommended. • Mogul storage link — mogul stove-room RH must be 5–10% below product ERH; otherwise jelly surfaces absorb moisture and become tacky. In an NKT design, ambient RH and dew point are continuously stabilised through closed-loop PID.

Calibration: refractometers should be verified weekly with pure water (0 °Bx) and a certified 60 °Bx reference solution.

NKT Application Link

For Brix-driven confectionery plants, NKT designs mogul stove-room and conditioning-tunnel climates based on the product's ERH. ADP2000-9500 silica gel rotor units stabilise 30–35°C / 25–30% RH year-round during 78–82 °Bx jelly production; dew point setpoint control runs independent of seasonal outdoor variation.

A typical NKT project scope includes: 1. Recipe-driven environment design — room RH and dew point derived from the Brix–ERH–RH triangle 2. Inline Brix sensor integration — inline refractometer data fed into the NKT climatisation system via PLC 3. NKT - Climate Track monitoring — hourly Brix–ERH matching, ambient RH deviation alarms, energy-use monitoring 4. Hygienic design — food-grade stainless inner casing, easy-clean filter cabinet, IP54 control panel

This integrated architecture has reference projects in jelly production that hold waste rates below 3% and reduce energy intensity (kWh/ton) by 35–45%.