Sponge cake

Sponge cake is a foam-type batter built by whipping eggs and sugar to incorporate air, then stabilizing the foam with flour (and sometimes starch). Classical formulas rely on mechanical aeration and protein coagulation during baking rather than chemical leavening, though variants may include a little melted butter or baking powder for specific applications.

Caloric value (baked product, 100 g)
Approximately 300–360 kcal per 100 g (typical ≈ 320–340 kcal/100 g, depending on egg:sugar:flour ratio, added fat, and residual moisture).

Key constituents
Egg proteins (ovalbumin, ovotransferrin, and yolk lipoproteins) forming the heat-set foam network.
Carbohydrates: sucrose, gelatinized starch, and dextrins.
Yolk lipids (triacylglycerols) and natural emulsifiers (phospholipids such as lecithin).
Water bound within the starch–protein matrix.
Micronutrients chiefly from eggs (B vitamins, choline) and flour minerals.

Average composition (indicative, per 100 g)
Water: ~20–28 g.
Total carbohydrate: ~55–65 g (sugars + starch).
Protein: ~6–9 g.
Fat: ~3–7 g (higher with added butter).
Dietary fiber: ~0.5–1.5 g.
Batter pH: near neutral to slightly alkaline due to egg white; it declines modestly on baking.

Production process
Ingredient selection: Fresh eggs at 20–24 °C, fine sugar, weak-to-medium wheat flour (W ~140–220), and optional starch to lighten structure.
Whipping: Whole-egg foaming, or separate foams (whites and yolks), to a pale, stable mass; target batter temperature ~24–28 °C for optimal volume.
Folding: Sift and gently fold flour (and starch) to avoid foam collapse.
Depositing and baking: Pan, then bake typically at 160–180 °C to set proteins and gelatinize starch with uniform golden color.
Cooling and equilibration: De-pan, cool on racks, and allow moisture redistribution before trimming or soaking.
In-line controls: Batter density, oven spring, crumb color, final moisture, and crumb integrity.

Sensory and technological properties
Texture: Fine, uniform crumb with elastic yet tender bite; minute cells from stabilized egg-white foam.
Rheology: Balance between protein coagulation and starch gelation; sugar elevates coagulation temperature and softens crumb.
Aroma: Sweet egg notes with light Maillard toast; added butter contributes dairy notes.
Water and stability: Medium–high aw; staling by starch retrogradation is mitigated by sugar and proper storage RH.

Food applications
Layer-cake bases, roulades (biscuit/joconde), charlottes and zuccotti, tiramisù variants using baked bases, pastry slices, and entremets. Cakes are commonly soaked with flavored syrups and filled with creams (pastry cream, chantilly, ganache, ricotta, mousses).

Nutrition and health
The profile reflects available sugars, starch, and egg proteins; fat derives mainly from yolk (and any added butter). Energy density is moderate-high. Major allergens: gluten (flour) and egg.

Quality and specification themes
High and regular specific volume; pale, even crumb with fine cells; no caverns or collapse.
Final moisture aligned with use (moister for soaking, drier for carving).
Elastic surface without deep cracking; uniform golden crust.
Process repeatability and full traceability under GMP/HACCP with CCP on bake lethality and allergen management.

Storage and shelf life
Keep wrapped/closed to limit moisture loss; plain bases hold 1–3 days at ambient conditions. Refrigerate soaked or filled products, balancing dryness risk. Freezing at −18 °C is suitable; thaw in closed packaging to prevent surface condensation. Controlled ambient RH slows staling; apply FIFO.

Allergens and safety
Allergens: egg and gluten; milk if butter is used. Microbiological risk is low after baking, but high aw bases become susceptible once soaked or filled: define CCP for rapid cooling, storage, and exposure time.

Troubleshooting
Low volume/dense crumb: Under-whipping or flour too strong → extend whipping to target density/temperature, select lower-W flour, or add starch.
Center collapse: Thermal shock or excess sugar/liquid → stabilize oven profile, bake longer, rebalance formula.
Rubbery crumb: Over-mixing after adding flour or overly strong flour → fold more gently, change flour grade.
Surface cracking: Oven too hot or insufficient initial humidity → lower temperature and manage moisture.
Rapid staling: Low aw/poor packaging → use barrier wraps, avoid drafts, and apply balanced soaking syrups.

Sustainability and supply chain
Impacts stem from eggs and wheat flour; responsible egg sourcing and local flours reduce footprint. Oven energy efficiency and batch planning limit waste. Cleaning effluents should meet BOD/COD targets; operations under GMP/HACCP ensure hygiene.

Conclusion
Sponge cake is a versatile technical platform for classic and modern pastry. Success depends on foam quality, balanced egg–sugar–flour ratios, gentle handling, stable bake profiles, and suitable storage to retain softness and workability.

Mini-glossary
pH — Measure of acidity/alkalinity; in foams it affects stability and protein coagulation.
W — Alveograph flour strength index: energy to deform dough; lower values suit sponge cakes.
aw — Water activity: Fraction of “free” water; medium–high aw supports softness but shortens shelf life.
RH — Relative humidity: Ambient moisture control that limits staling and cracking.
GMP — Good Manufacturing Practice: Hygiene and process controls ensuring consistency and traceability.
HACCP — Hazard Analysis and Critical Control Points: Preventive food-safety system with defined CCPs.
CCP — Critical control point: A step where control prevents, eliminates, or reduces a food-safety hazard.
FIFO — First in, first out: Inventory rotation—use the oldest lots first.
BOD/COD — Biochemical/Chemical oxygen demand: Measures of organic load in effluents for environmental management.