Despite existence for millenia, ovens keep transforming and improving

Cooked food has been a part of our civilization for thousands of years. Throughout the Mediterranean, Africa and the Roman Empire, wood fires in a stone enclosure have been used to broil meat and bake bread. This was the basic premise for the oven, as it provided a different heat source for cooking compared to the open-air fire used to heat water and make soup. The first official oven in recorded history was built in 1490, in France and made using brick and tile.

Fast forward to the 21st century, the oven is often the anchor of a busy household, helping to prepare Sunday roasts, goodies such as cakes and cookies, as well as the (occasional) frozen pizza to crispy perfection. Without an oven, your kitchen almost seems bare.

Fundamentally, baking may seem to be a rather static topic: mix flour, water, leavening and various flavoring materials, and heat the mixture to gelatinize starch and denature the protein. However, this millennia-old process has been undergoing rapid change during this century, and even more during the last two decades. The fantastic advancements in the sector over the years have enabled manufacturers to churn out ovens with many features, making them more and more intuitive and practical. From robotics and extrusion to data analytics and new learning techniques, advancements in oven technologies are adding value in bakeries across the world.

Heat sources and transfer mechanisms in baking

Baking is made possible by thermal energy. The energy is heat and it can be generated from many sources. Some ovens heat materials using the combustion of a fuel, such as wood, coal, or natural gas (e.g., natural gas, propane, butane, liquid petroleum gas) while others heat materials by exposing them to microwave radiation or resistive heating. In conventional baking processes there are three general ways heat produced from these various sources can be transferred to the dough piece, namely radiation, convection and conduction.

Radiant heat consists principally of invisible infrared rays that emanate from the heated internal surfaces of the oven. Its behavior differs from the other types of heat in two distinct ways: it is blocked in its transmission by any intervening opaque object, and it is highly responsive to the absorptive properties of the product that is exposed to it.

Convected heat is that which is transferred by means of inter-mixing fluid media such as air, water, vapor or combination gases. In ovens, convected heat is distributed through the baking chamber by the turbulence of the internal atmosphere and is transferred by conduction to the dough piece when the hot air contacts the dough surface. The hot air enters the oven chamber through perforated pipes or plates, called “coloraiders,” located above and below the product. It is recommended that the air is blown onto the product in a defined pattern to provide good color development and maximum heat transfer.

Conducted heat is that which is transmitted by physical contact from one body to another or from one part to another in the same body. Thus, the side and bottom crusts in pan bread result mainly from the heat that is transmitted by the walls of the pan while the gradual heating of the interior of the dough piece during baking is largely the result of heat conditions inside the bread.

While all three modes play significant roles in baking, their relative importance depends largely on the type and design of the oven. As Ann Wells, commercial director at Brook Food & Bakery Equipment explains, “Different types of ovens have different heat transfer concepts and are therefore built-in different ways.”

Convection Oven: The go to oven for large bakeries

Convection ovens are arguably some of the most widely used ovens, both domestically and industrially. These ovens have heating elements at the top and the bottom of the oven cavity. They are also equipped with a fan that helps circulate hot air throughout the oven cavity, helping to reduce hot and cool spots for more even results.  Convection ovens can also have a third heating element, called True Convection, to help foods cook faster by distributing hot air around the top, bottom and sides of the meal.

These ovens are particularly ideal for baking as they may eliminate the need to rotate dishes in the oven.  These ovens are heated by hot water, gas and electricity and the heat generated from these sources are introduced into the oven by convection. Two designs of these ovens exist commercially: batch or continuous. Batch ovens are used when all materials being heated need the same temperature and duration. Continuous ovens remain at the same temperature and sometimes have a rotating section creating a conveyor belt.

Category wise, convection ovens, like many others fall under two categories: direct-fired and indirect-fired. They can be powered using gas (the most common), oil, or electricity. The way direct- and indirect-fired ovens transfer heat is similar, with the main difference being whether or not the food products come into contact with the products of combustion: in a direct-fired oven, ribbon burners placed above and below the oven band heats the baking chamber directly, thus the food products come into contact with combustion products; in an indirect-fired oven, the burners heat a heat exchanger, which transfers the heat into the baking chamber.

Direct-fired ovens are ideal for products that require high temperatures and short baking times and Indirect-fired ovens are better for products that require lower temperatures and longer baking times. In both, the infrared radiation provides a stable penetrative heat transfer, creating products with excellent volume, texture and flavour.

Rack oven & reel ovens: the ideal partner for retail bakers

A rack oven is a vertical oven into which racks full of sheet pans can be wheeled for baking. This unit can hold 8 to 20 sheet pans per baking cycle. Some units make use of electric or fuel sources, and place fans inside the baking chamber (generation of convection drying) to speed up baking times and to develop special features in the products. This oven is suitable for retail operations due to its floor space economy, and medium to long baking cycle times. These ovens usually have programmable (saved) recipes so that the operator can change baking time and temperature, intensity of air ventilation, and steam impingement frequency.

In a reel oven, trays or shelves are placed on platforms rotating on a central horizontal axis. They are normally directly fired with gas or electricity, with the heating source located centrally across the floor of the chamber.  Reel ovens often do not generate uniform distribution of heat transfer due to their revolving nature and interfering structure for radiant heat transfer. Products placed on sheet pans or trays continuously rotating may present uneven coloring or poor final moisture distribution. This type of oven is mostly designed for retail bakeries or baking plants with small-scale production.

Tunnel & Conveyor ovens: When flexibility is a priority

Tunnel ovens are continuous mode operation baking units that typically have a long baking chamber (usually more than 80 meters in length), which goes from one side (loading point) to another (unloading point) in a straight conveying band. The conveyor band material may be built of wire mesh or carbon steel sheets. Tunnel ovens are commonly powered by fuels such as natural gas (used for baking), and electricity (for powering air circulation and conveying system). The baking chamber may be divided into several baking zones which makes the application of a temperature sequence possible, providing the baker with more flexibility in baking conditions and more complexity for controlling baking parameters.

Conveyor ovens, on the other hand, have two parallel endless conveying chains that carry trays of products through the length of the baking chamber, so the dough pieces continually enter and leave the oven. Their main advantages are simplicity of design, and uniformity of baking as the products travel the same path through the baking chamber. A motor drive directly controls band speed, thereby determining baking cycle time. Conveyorized ovens may be single-lap or double-lap. In single-lap ovens, the trays containing the products travel a single pass (back and forth). The trays in a double-lap oven travel through four heat zones instead of the two zones of the single-lap oven.

Sustainability drives innovation in Oven technology

Rising fuel costs and bakers’ desires to achieve more sustainable operations through more efficient heating mechanisms have prompted oven manufacturers to redesign their industrial ovens. Notorious for their harmful pollutant generation, Gas ovens have had to undergo various developments to cut down on their carbon footprint. The Kitchen Range Hood, an overhead ventilating system consisting of a device containing a mechanical fan that hangs above the stove or cooktop in the kitchen is one of the solutions aimed at curtailing these emissions. These wondrous invention sucks up the polluted air and filters it (as with a ductless model) or is carried to the exterior (with a ducted model). A more subtle alternative to the typical vent hood is the downdraft hood, which vent through the floor. There are some models that can be hidden into the oven’s cabinet layout while others have a telescopic feature, so they can rise from the cooktop with the touch of a button. 

AMF Bakery Systems have also introduced an emission-free, direct-fired, hydrogen-fueled tunnel oven. The modular Multibake VITA Tunnel Oven by AMF Den Boer allows bakers to reduce carbon dioxide emissions by 99.9% within the baking process while reducing the cost of utilities. Bühler Group is working to develop environmentally friendly solutions, and its bestselling convection oven, the Meincke Turbu, provides sustainable production and minimal CO2 emissions. Bühler’s sustainability goal of reducing waste, energy and water usage by 50% in its customers’ value chains by 2025 is also made more possible with the new Meincke Turbu 4. Turbu 4 can use both gas and electric heating sources. If operated with gas, harmful emissions are minimized by low NOx burners. If electric, there are zero emissions.

From robotics and extrusion to data analytics and new learning techniques, advancements in oven technologies are adding value in bakeries across the world.


Efficient ovens make high quality products

A need by manufactures to make high quality products in a reproducible way have prompted the invention of novel technologies that address shortcomings which exist in standard baking ovens. Development of hot spots is one of the great drawbacks in standard convection ovens as it greatly reduces their efficiency. Seeking to enhance efficiency, manufacturers are actively launching convection ovens which have features that ensure even heat distribution inside the oven chamber. For instance, Alto-Shaam provides commercial gas convection ovens that are equipped with its patented transverse-flow burner system that ensures there is even hot air distribution inside the cooking chamber, reducing the need to rotate the pans for consistent cooking.

The baking process demands a high amount of energy, but only one-third of the total energy supply to the baking oven is actually used for baking, while the rest is dissipated to the environment. This implies that the energy input to the baking process can be significantly reduced. Vulcan is pushing to ensure greater energy use with the launch of its energy efficient VC5G gas convection oven. VC5G is independently certified by ENERGY STAR with a 56% cooking efficiency rating, the highest ever awarded to a full-size gas convection oven. This appeals to the ever-growing environmentally conscious customer base, who have shown a clear preference towards the product.

GEA, a company with a longstanding history in oven technology recently launched CookStar 1000 Gen 3 industrial spiral oven, which through a combination of optimized airflow, climate control and dynamic exhaust system ensures energy is used exactly as and when it is needed and reduces heat and steam losses. Auto-Bake, another baking solution provider has launched an electric alternative to its direct-gas fired convection oven. Scott McCally, President, Auto-Bake Serpentine, said this oven is 40% more energy efficient than its standard gas-fired model, owing to both heating system design and their low surface area to volume ratio.

Self-cleaning ovens

As fun as baking could be, or even easy, owing to the numerous advancements that have streamlined the process, having to take soap and water to the greasy aftermath is often grueling for most people. Not to worry, oven cleaning has now been made vastly efficient by the invention of self-cleaning ovens. Self-cleaning ovens have a feature called pyrolytic cleaning. The oven heats itself to an extremely high temperature, which burns away any food residue inside and turns it to ash, which can be easily removed by running a damp cloth over the inside. Since General Electric introduced the first oven with a self-cleaning feature in 1963, these baking marvels have seen great advancements. For example, Whirlpool’s 5.0 cu. ft. Front Control Gas Range with Cast-Iron Grates Oven features adjustable self-cleaning settings, which allow you to pick a cycle based on the amount of ash your oven has, from light, to moderate to heavy.

Smart ovens remove the guesswork from baking

The need to have consistent and reproducible baking results prompted the invention of smart ovens which closely regulate and automate the baking process. In smart ovens, touch screen controllers enable one to easily adjust and set baking temperatures. Like with most “smart” appliances, what separates smart ovens from more-conventional ovens is their connectedness. These Wi-Fi and or Bluetooth enabled devices allow you to control your baking using your smart phone.  

ITW Food Equipment Group is a pioneer in the field of high tech ovens. Its SmartConnect app allows users to gain important insight into how equipment is being used, monitor sanitization status, water and energy consumption, and reduce downtime with equipment status and email alerts notifying users about machine errors. “Our customers are becoming more digitally savvy every day. Having real time access to equipment usage information and alerts helps them maximize productivity of uptime and minimize the impact of downtime,” said ITW Food Equipment Group director of marketing Todd Blair.

AI technology has also been incorporated into ovens, and this could make end user training a thing of the past. An ideal example is TurboChef Technologies which provides commercial convection ovens that come equipped with over 3,500 pre-programed cooking menus, which helps the operator to select different food menus and achieve consistent cooking results every time.

What to look for when buying an oven

When buying an oven, clearly there are a lot of options, but your bottom line remains ensuring you are selecting the best oven to suit your needs. Most important is deciding the setting in which you intend to use your oven, be it commercially or in your home. If intended for commercial use it is important to know the capacity of your production and to choose an oven that will accommodate your output. The other size of the coin would be size. If you operate in a facility where there are strict space requirements, with limited floor space and lots of different units to accommodate, you may want to go for one that is economical on space. In a commercial bakery, not all bakers are experts. This means that the oven should be simple and easy to use. For this purpose, you can choose an oven with manual or pre-programmed cooking modes.

Additionally, for both commercial and at home ovens it is important to decide on your preferred a heat source and to also look for other efficient features like energy saving labels as well as ease operation features like intuitive touchscreen technology as well as the ability to give reproducible results.Lastly, you need to go for a reliable oven. A malfunctioning commercial oven can be disastrous for your business. Apart from losing the investment in such a purchase, it may also cut down your profits. Make sure to go for a product that is durable and reliable.

This feature appeared in the August 2022 issue of Milling Middle East & Africa. You can read this and the entire magazine HERE