In food ingredient manufacturing, process times and energy consumption can be reduced significantly when recipe, raw-material quality, drying or mixing method, automation and utility supply are coordinated with one another. However, there are no uniform best values for all products. Milk and whey products, proteins, starch products, flavourings, spice blends, functional powders and plant-based ingredients differ considerably in moisture, viscosity, temperature stability, particle structure, hygiene risk and cleaning effort.

Meaningful benchmarks therefore always relate to a clearly defined unit. For drying processes, this is usually the energy expenditure per kilogram of water evaporated. For mixing processes, it is, for example, mixing time, energy input per batch, number of batches per hour, or the homogeneity achieved. For complete production lines, output, scrap rate, cleaning duration, water consumption and overall equipment effectiveness are additionally considered.

Short process times

In spray drying, the contact and drying times of the individual particles in the drying gas are often in the range of seconds. However, the total residence time of the product in the plant also depends on atomisation, the drying chamber, post-treatment, discharge and possible agglomeration. High throughput can only be combined with stable product quality if solids content, viscosity, atomisation, air temperatures and air volume flow are matched to the product.

In fluidised-bed processes, drying, cooling and agglomeration can be combined in a single plant. The required process time is often in the range of minutes up to an hour and is influenced above all by the initial moisture, the desired residual moisture, the particle size, the thermal sensitivity and the required product structure. Particularly for instant products, integrating several process steps can shorten the overall production sequence.

With band dryers, the process time depends strongly on layer thickness, air routing, temperature profile and product properties. Multi-zone concepts and targeted air routing can accelerate drying without impermissibly raising the product temperature. Comparison of plants should therefore not be based on residence time alone, but should always also consider residual moisture, product yield, colour, aroma, solubility and nutrient retention.

For mixing processes involving dry or slightly moist food ingredients, modern mixing plants can achieve high homogeneity within a few minutes. However, the actual mixing time must be verified with the real product. Differences in particle size, bulk density, moisture, agglomerate stability and dosing accuracy can significantly change the required mixing time. A very short mixing operation is only advantageous if the recipe is distributed evenly and sensitive particles are not damaged.

Cleaning duration is a central factor for overall productivity. It comprises not only the actual CIP or WIP process, but also product discharge, changeover, release and, where applicable, microbiological checks. Optimisations such as separately cleanable process areas, demand-based cleaning programmes, conductivity measurement for endpoint detection, and improved mechanical cleaning action can significantly reduce CIP times. Industry analyses cite potential reductions of roughly 25 to 40 percent in CIP cycle times, provided microbiological validation is maintained.

Overall equipment effectiveness is an important metric for evaluating complete food lines. It combines availability, performance and quality rate. A value of 85 percent is often cited as a general benchmark, but originates primarily from discrete manufacturing and cannot be applied across the board to food processes because of mandatory cleaning, allergen changeovers and product-specific hygiene measures. For food and beverage plants, values of roughly 55 to 70 percent are typically cited. Well-run plants can achieve roughly 75 to 80 percent, while higher values depend strongly on the product type, the variety of variants, and correct treatment of planned cleaning time.

Low energy consumption

In drying processes, the evaporation of water is the most important energy lever. Spray drying is indispensable for many high-value powders but is among the more energy-intensive processes. Depending on the product, initial moisture, air routing and heat integration, specific consumption can vary considerably. Sources cite values of up to 6,000 kilojoules per kilogram of water evaporated for conventional spray drying. Significantly lower values are reported for more efficient drying concepts. Energy consumption should therefore always be evaluated in relation to the amount of water evaporated and additionally to the amount of product produced.

An important saving opportunity is pre-concentration ahead of thermal drying. If liquid products are first concentrated by membrane filtration or evaporation, less water needs to be removed in the subsequent dryer. The choice of method depends on product stability, viscosity, membrane sensitivity, the desired concentration and cleanability.

Multiple-effect evaporators and mechanical vapour recompression can significantly reduce the energy demand for concentration. As a point of reference, a single-effect evaporator requires roughly 2,260 kilojoules per kilogram of water evaporated. A four-effect evaporator can theoretically reduce the specific steam demand to roughly 565 kilojoules per kilogram. For systems with mechanical vapour recompression, significantly lower values are reported, though the demand is then assessed mainly as the electrical energy consumption of the compressor.

Heat recovery is often the most effective approach for energy-intensive food processes. Exhaust air, condensate, vapour and cooling streams can be used to preheat fresh air, process water or product precursors. How high the actual recovery rate turns out to be depends on temperature differences, fouling tendency, hygiene concept, available heat sink and operating hours. Instead of a general recovery rate, operators should therefore have a site-specific heat balance and a pinch analysis prepared.

Electrical consumers also affect the overall balance. These include fans, pumps, vacuum generators, mills, dosing units, conveying equipment, refrigeration systems and compressed-air systems. Highly efficient motors, correctly sized variable-frequency drives, low pressure losses, speed-controlled fans and systematic leak control for compressed air often reduce consumption without changing the actual product or recipe process.

For comparing complete plants, energy consumption per kilogram of end product is only helpful if the system boundaries are clearly defined. Operators should clarify whether it includes only the direct electricity consumption of the process plant, or also steam, refrigeration, compressed air, hot water, CIP media, exhaust-air treatment and energy losses from central supply. Only then can plants or production sites be seriously compared with one another.

Key influencing factors

The achievable metrics are determined above all by the solids content of the starting products, the moisture, the thermal sensitivity, the viscosity, the desired particle structure and the variety of recipes. Even a higher input concentration can significantly influence the energy demand of the subsequent drying. Conversely, fluctuating raw-material quality can lead to longer process times, more re-adjustment, higher scrap and additional cleaning effort.

Hygienic plant design also affects time and energy. Well-drainable apparatus, short product paths, as few build-up points as possible, and cleaning matched to the product reduce product losses and downtime. However, hygienic design must always be compatible with requirements for allergen control, microbiological safety and product changes.

Automation and data evaluation help make energy and time losses visible. Process control systems and manufacturing execution systems can record metrics such as specific heat demand, power consumption, batch duration, cleaning time, scrap and equipment downtime. Measures can be derived from this, for example optimising temperature profiles, shortening changeovers, reducing idle times, or adjusting cleaning programmes.

Classifying the benchmarks

A realistic target should not start from a single industry-wide figure. It is more sensible to establish a product-specific baseline value, recorded separately for each line. Building on this, clear target values can be defined for throughput, cycle time, energy per kilogram of water evaporated, energy per kilogram of product, water consumption, cleaning duration, scrap and overall equipment effectiveness.

One example is the production of a spray-dried protein powder. Pre-concentration reduces the amount of water that has to be evaporated in the spray dryer. Improved exhaust-air heat recovery lowers the heat demand. A stably controlled drying process reduces over- and under-drying. At the same time, an optimised cleaning concept can shorten the changeover time between two product campaigns. Whether these measures are economically worthwhile depends on the product value, the operating hours, the energy costs, the quality requirements and the existing utility networks.