BISCUIT PRODUCTION B
iscuit manufacturers, in line with so many other sectors, are facing increased pressure to demonstrate their commitment to sustainability by reducing their carbon footprint and overall environmental impact, to meet changing regulatory requirements and the demands of consumers and customers. For biscuit producers a good place to start the carbon reduction journey is to focus on the most energy-hungry processes – which is usually the oven. An interesting study, which investigated the feasibility
of electrification of its gas-fired industrial baking ovens used for biscuits and other products, has been undertaken by Burton’s Foods – now operating as Fox’s Burton’s Companies (FBC) UK under a Ferrero-related company – working alongside product design and innovation company, 42 Technology (42T). The study, entitled Industrial Fuel Switching Feasibility StudyProject Zap – Electrification of Biscuit Production, was funded by the UK Government as part of an Industrial Fuel Switching Competition, which aims to accelerate the transition to cleaner fuels for manufacturers relying on oven-based operations. Electrification is considered to be the most viable route to de-carbonisation in the bakery sector. A view supported by The Food and Drink Federation (FDF), which has estimated that direct-fired ovens used within the UK’s food and drink sector contribute around 700,000 tonnes CO2e per year. Industrial biscuit production has traditionally relied on the
use of natural gas-fired ovens to produce biscuits with the flavour, texture and appearance that appeals to consumers. So, the FBC study needed to consider both technical and commercial aspects of fuel switching to ensure that biscuit quality, costs and throughput could be maintained or improved. The company’s legacy fleet of gas fired ovens and the variation in key parameters, highlighted that oven design and operation often relies on expert knowledge about how a particular oven is run and tuned in response to different ingredient batches and changing external environmental conditions. Characterisation of the current process and equipment was therefore required before they could look at replicating the baking process using electrical heating.
Quality issues
The first challenge in replacing gas fired ovens with electric is to determine if electric heating can produce products of the same quality. The four key parameters that affect the quality of the finished output of a biscuit from an oven are heat flux, temperature, air speed and humidity. Because the baking process involves chemical reactions that take place within the dough pieces, there is also a time element to these parameters – how long the product is exposed to the baking conditions and how the conditions vary along the oven are therefore key pieces of information that need to be known to completely characterise the existing oven. To collect this data, as part of the FBC study, 42T was
tasked with characterising the thermal and humidity profile of the gas-fired industrial baking line; mapping the energy losses within the process to identify potential savings; and investigating commercially-available electric ovens to replicate the existing baking process. The team also developed a process to assess and reconfigure other production lines
bakeryproduction.co.uk
relying on electrical heating technologies. It was important that the total energy requirement is minimised, not just for resource efficiency, but also to mitigate against the higher cost of electricity when compared to gas, currently. Ovens transfer heat to the biscuits through a mixture of convective, radiative and conductive heat flux. In direct gas fired ovens, the ratio of the two is controlled by the gas input rate, and the amount of air recirculation and extraction rate. A minimum extraction rate needs to be maintained to ensure combustion gases are not vented into the workspace around the oven.
Electric heating elements produce radiative heating. Convective heat flux can also be achieved, with electrically heated air being forced over the product surface. Both gas and electrical ovens should be capable of producing the same temperature and heat flux characteristics for the products, and an example electrical oven was selected for this comparison for the study.
Burton’s Foods biscuit range.
The humidity within the baking chamber is determined by a balance between the moisture produced from the combustion process (in the case of gas fired ovens), the moisture removed during baking and the extraction rate from the oven. Comparing direct gas fired and electric ovens, an electric oven can achieve a wider range of operating humidity conditions as the extraction of combustion gases is not necessary. The airflow around both ovens would be expected to be heavily influenced by any fans and the belt motion.
The results from the feasibility study concluded that although there are suitable electric ovens available – even with all of 42T’s recommended energy savings and other operational cost reductions factored in – they would still make the baking process more expensive because of the
The Food and Drink Federation has estimated that direct-fired ovens used within the UK’s food and drink sector contribute around 700,000 tonnes CO2e per year”
Kennedy’s Bakery Production August/September 2023 15
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