Professor Greiner, how did you approach the study, and what were your objectives?

The trigger was a similar study conducted around ten years ago. Our goal was to achieve practical, scientifically based results by conducting measurements in a real commercial kitchen rather than a laboratory. The study was conducted at the AXA Group's catering facility in Cologne, operated by Eurest. It was important that we had a realistic environment with typical processes and employees. This is the only way to ensure that the results can be transferred to other companies. In a laboratory, for example, it is not possible to replicate reality. The decisions made by team members in the kitchen are also important: which cooking system do they use, for how long, and why not another one?

How did you ensure that the measurement results before and after the kitchen renovation were comparable?

To this end, the two three-month measurement phases took place during similar seasons, with almost identical recipes and comparable menus. Minor deviations were minimised by the long measurement periods. The personnel structure also remained unchanged. Additionally, we defined reference dishes, such as meat stew with penne, chicken breast with pointed cabbage and potato dumplings (schupfnudel), as well as two vegetarian dishes, to establish a detailed, uniform basis for comparison. Any minor deviations due to changes in processes, such as using combi-steamers for cooking pasta instead of large tilting pans, pre-production, chilling and regenerating components, were meticulously documented. These changes were part of the study, alongside energy and water consumption.

What challenges arose during the measurement process?

For example, kitchen processes changed due to new cooking system technology. In some cases, the switch was made to cook and chill methods, which naturally affects energy consumption throughout the entire process.

A chiller was occasionally used in the old kitchen. However, this was not a fixed step in the process. In the new kitchen, pre-production, i.e. delayed cooking, forms part of the concept and therefore accounts for a higher proportion.

Any irregularities, such as defective appliances or operating errors, were documented and taken into account. We deliberately did not intervene in the processes or correct anyone's actions, but observed and documented the procedures realistically in order to obtain valid results.

How much has the new kitchen technology saved in terms of resources?

Overall, we measured a 24.1 per cent reduction in energy consumption per meal. Water consumption (hot and cold) has been reduced by an even greater amount: 47.9 percent per meal. The latter is largely due to the new cooking systems' more efficient cleaning processes. For instance, a new combi-steamer with an automatic cleaning function uses around 50 litres of water per cycle, whereas a traditional boiler can use up to 350 litres for cleaning.

Which specific factors have saved energy?

These are several factors. Firstly, the new cooking systems are much better insulated. Secondly, the cooking systems' smart control and regulation plays a decisive role. The cooking systems provide exactly the right amount of energy. Thirdly, the reduced use of materials in modern cooking systems is important. Put simply, much less mass needs to be heated up. The amount of steel in a conventional tilting pan exceeds that in the multifunctional iVario cooking system by a considerable margin. Finally, new technology enables more efficient work processes that avoid additional energy consumption.

How does peak load affect a kitchen's energy costs?

Peak loads are measured at 15-minute intervals and determine the monthly supply fee charged by energy suppliers. In this case, the new technology has significantly reduced peak loads, which will lower costs considerably in the long term. Peak load usually determines monthly energy costs, with the calculation based on the highest value within a month.

Are there further potential savings in the examined kitchen?

Yes, definitely. For example, cook & chill processes have not yet been fully optimised. In addition, targeted training and process optimisation could deliver further savings. However, it would not be reasonable to make a concrete statement about the amount of potential savings. If new processes are not consistently adhered to, for example, this data is also reflected in the measurement: If someone forgets to take 20 kilos of chicken legs out of the freezer the night before to defrost, they have to be cooked from frozen at lunchtime. It's not an ideal process, but it's the reality. In a busy kitchen, the focus is undoubtedly on guest satisfaction rather than resource consumption.

What role does team training play in introducing new technology?

It is crucial. It's not just about learning to operate the new cooking systems. Rather, it's about exploring new possibilities in terms of timing, starting in the morning and cooking different products at the same time. New routines must be established with the cooking systems. This is the only way to ensure that the new technology is used in an optimal, quality-oriented and resource-efficient manner. Regular training should be provided to prevent a return to old routines.

What are your three key arguments for investing in modern kitchen technology?

Firstly, the proven energy and water savings are a decisive economic argument. Secondly, modern technology makes the daily work of kitchen teams much easier, which is particularly important given the shortage of skilled workers. Thirdly, the technology enables significant improvements in product quality, such as shorter holding times and gentler preparation.

So not only are resources being protected, but nerves too?

When used correctly, just-in-time finishing reduces food waste, which is another economic advantage and a benefit for climate protection. A much more relaxed working atmosphere for teams is created when production processes can be organised at different times, which also improves product quality. In the past, some kitchens started at 6 a.m., with the first components ready by 8 a.m., and then they were kept warm for hours until they were served.

Today, the new kitchen plans are based on the point of serving, i.e. the guest's perspective. Service starts at 11:30, so a lead time of just 10 minutes is enough to put a baking tray of fresh chicken fillets in the combi-steamer. Post-production runs smoothly in parallel with service, ensuring minimal warming times until the food reaches the plate. The starch side dish is pre-cooked and chilled the day before. It can be served in a few minutes — also in the combi-steamer — and is fresher than if it had been produced on the day of serving with longer warming times.

What do your study results mean for the hospitality industry as a whole?

This study demonstrates the potential savings of modern kitchen technology in a practical and realistic way. These results can be applied to other businesses. The processes and challenges in commercial kitchens are comparable. The findings can help decision-makers in the hotel, catering, and communal catering sectors to make informed investment decisions, making their businesses more economical and efficient in the long term, as well as more employee-friendly.

Michael Greiner studied ecotrophology, writing his doctoral thesis on 'Microwaves and Steam for Food Preparation'. He then worked in appliance development for 12 years. He has held the Chair of System Catering and Catering at the Weihenstephan-Triesdorf University of Applied Sciences for the past 15 years. His research focuses on catering technology and supply management.