Proposal of Dynamic Thermo-Hygrometric Profiles for Shape, Structure, and Texture Control Using E-LSIV Technology
1. Introduction and Industrial Context
Biscuit baking is traditionally classified as a “dry” thermal process, where product quality is assumed to be governed primarily by oven temperature, residence time, and conveyor speed. In industrial practice, the use of steam is often absent or considered unnecessary, due to the low moisture content of biscuit doughs and the lack of yeast-driven volumetric expansion.
Nevertheless, a wide range of quality defects commonly observed in industrial production—such as surface cracking, warping and curling, non-uniform coloration, and variability in hardness and friability—cannot be fully resolved through formulation or temperature adjustments alone. These defects are frequently linked to excessive thermo-hygrometric gradients during the early stages of baking rather than to recipe design.
2. State of the Art: Limitations of “Dry Baking”
Continuous biscuit ovens (tunnel, convection, impingement, or hybrid designs) are typically engineered to deliver high heat fluxes at the oven entrance in order to maximize throughput and ensure rapid moisture removal. While effective from a productivity standpoint, this approach often leads to rapid surface dehydration while the core of the product remains plastic.
The resulting premature surface stiffening (case hardening) restricts stress relaxation within the dough matrix. As baking progresses, internal stresses develop due to differential shrinkage and moisture migration, leading to cracking, deformation, or loss of dimensional consistency. In this framework, the process lacks a mechanism to moderate early-stage heat transfer.
3. Physical Hypothesis: Steam as a Heat-Transfer Moderator
Unlike bread baking, where steam is primarily used to promote oven spring and delay crust formation, the role of steam in biscuit baking must be reinterpreted. In this work, steam is proposed as a process variable for controlling heat transfer and evaporation kinetics, rather than as a hydration agent.
The introduction of small amounts of high-quality (dry) steam during the initial phase of baking can:
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reduce excessive surface heat flux;
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homogenize convective heat transfer;
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temporarily slow down moisture evaporation;
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promote visco-plastic relaxation of fat–sugar–starch matrices.
Crucially, the effectiveness of this approach depends not on steam quantity, but on steam quality (dryness fraction) and precise temporal control.
4. Biscuit Baking Stages and Thermo-Hygrometric Requirements
The biscuit baking process can be schematically divided into four main stages:
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Initial heating and dough relaxation (0–2 min)
Softening of fats and reduction of dough viscosity. Excessive heat input at this stage fixes geometry prematurely. -
Evaporation of free water (2–6 min)
Moisture migrates toward the surface; steep gradients induce internal stresses. -
Structural setting and glass transition (6–10 min)
The biscuit structure stabilizes; residual moisture content critically affects texture. -
Final drying and coloration (>10 min)
Maillard reactions dominate, defining color and crispness.
Each stage exhibits distinct thermo-hygrometric requirements, which are difficult to satisfy using static oven conditions.
5. Dynamic Steam Profiles and the Role of E-LSIV
The E-LSIV technology enables the implementation of dynamic steam profiles characterized by:
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very low steam flow rates;
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high steam quality (minimal liquid condensation);
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rapid response times;
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high repeatability and recipe-based control.
For different biscuit categories (shortbread, dry biscuits, soft cookies), tailored profiles can be designed in which a brief, controlled input of dry steam accompanies the initial heating phase, followed by rapid steam exclusion to allow final drying and color development.
6. Expected Benefits and Industrial Implications
The proposed approach is expected to deliver:
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improved dimensional stability;
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reduced cracking and deformation;
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more uniform surface coloration;
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improved repeatability of texture at constant formulation;
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wider processing windows and reduced production scrap.
7. Conclusions
In biscuit baking, steam should not be regarded as a legacy tool borrowed from bread production, but as an advanced process variable for heat-transfer engineering. The controlled use of high-quality steam, enabled by E-LSIV technology, provides a new degree of freedom for stabilizing biscuit baking processes and improving industrial product consistency.
