Food Rethermalizer vs Food Warmer: What’s the Difference?

rethermalizer vs warmer

Having the right tools for the job makes all the difference. In a commercial kitchen, food rethermalizers and food warmers are two important tools. You might think these appliances do the same thing. However, their function is very different. Each has unique benefits.

What is a Rethermalizer?

In general, rethermalizers are appliances designed specifically to reheat prepared foods from a chilled or frozen state of less than 40°F to a temperature of more than 165°F safely and quickly. They don’t require food to be slacked or thawed before retherming. Rethermalizers must be capable of boosting food temperature through the “Danger Zone” (between 40°F and 140°F) in under two hours (not to be confused with Kenny Loggin’s classic Danger Zone). This is critical because bacteria reproduction goes into overdrive within that temperature range, doubling every 20 minutes. Once food passes 140°F those little bacterial bastards are killed off.

Most rethermalizers use water as a heat transfer medium.

rethermalizer vs warmer

Uses for a Rethermalizer

Just as the name implies, rethermalizers reheat food. They are especially useful in operations that prepare and freeze large batches of food ahead of time. Ideal menu items for retherming include soups, casseroles, sauces, pasta, vegetables, bread, desserts, and meats.

We all know that finding good help right now is a royal pain in the butt. With no end in sight to the tight labor market, it’s important to have tools that are easy to use and don’t need a lot of babysitting. Rethermalizers are a great option. They’re push-button simple, and most feature an automatic hold function. Many have programmed cooking functions, so staff can just load them up and push start.

Types of Rethermalizers

There are four basic types of rethermalizers: water bath, induction, combi oven, and CVap® Retherm Ovens. The first two are typically countertop appliances (though some large floor models are found in QSR chains). The latter two are usually floor models.

Bain Marie or water-filled rethermalizers use a water well to reheat food quickly and gently. Although this type can be a more economic option, there are a couple of disadvantages. Water-filled rethermalizers need about 15 minutes to preheat before adding the product. And it’s necessary to check the water level about every two hours. Allowing the water level to drop too low can damage the unit and burn the food.

Some water bath rethermalizers are sous vide immersion circulators. Food is prepped and sealed in vacuum bags. It can be cooked right away, or chilled or frozen for later use. The bagged products are placed directly in the heated water bath. Once it reaches serving temp food can remain in the water bath until serving. The water bath prevents it from overcooking or cooling down.

Induction rethermalizers remain cool until an induction-ready inset is placed inside. They are very efficient since no energy is expended in preheating. Virtually all heat is inducted directly into the food, quickly retherming it. Because induction units don’t utilize water baths, they won’t develop the funky scaling that can develop in water bath appliances.

rethermalizer vs warmer
foodservice products

Combi ovens are popular for rethermalizing. Combis get their name from their combination of hot steam and hot convected air to quickly retherm food. They are hella fast, and hella powerful. But they’re also hella expensive and can be pretty damned complicated to use. Speaking of expensive, you’ll want to factor in the required chemicals and maintenance that combis must have.

Like CVap Retherm Ovens, combis don’t just thermalize. Most are capable of a wide range of other cooking processes.

CVap Retherm Ovens use heated water vapor as their primary heat source. This means you can retherm in a CVap oven with or without vacuum bags. It’s like sous vide, without the mess. CVap ovens can also roast, steam, bake, sous vide, low-temp steam, proof, and more. You can even use them as food warmers. They automatically shift from cooking to holding mode at the conclusion of their cooking cycle.

Rethermalizers vs. Food Warmers

Rethermalizers can be used as food warmers. But food warmers cannot be used as rethermalizers. They perform very different functions. Rethermalizers are designed to quickly heat food to safe temperatures. Although food warmer might sound like it does the same thing, that’s not the case. Food warmers are designed to keep hot cooked food at a safe temperature. They aren’t designed to heat up cold food. If anybody tells you different, they are either pulling your leg or are ignorant to the basic functions of kitchen equipment.

What is a Food Warmer?

Food warmers maintain food temperatures above the minimum safe temperature of 140°F. They are called several different things: warmers, holding cabinets, hot boxes, warming drawers, etc. Food warmers are great for operations that have predictable rush periods, like school cafeterias and fast-food restaurants. They allow cooking to be done ahead of the rush. Food is held hot until serving. This allows more efficient use of the staff on hand. Just like rethermalizers, many warmers rely on heated water in some form to provide continuous heat.

Uses of a Food Warmer

As the name implies, food warmers keep food warm. They are useful in rush traffic situations and in operations that need to serve throughout the day. Food warmers help provide quick service by minimizing prep time.

food warmer

Types of Food Warmers

Food warmers come in all shapes and sizes. Some are simple, such as chafing dishes, heat lamps, warming shelves, and heated strips. The simpler warmers are only good for short-term holding, like on a serving line.

Countertop warmers are next up in the holding hierarchy. They include kettles, bins, and drawers. Kettles are great for soups and sauces. Bins usually hold full or fractional pans, so you can hold different products together (if they share similar settings). Warming drawers are great because they have a closed environment, enabling more precise control of food temperature. Drawers take up relatively little space, making them ideal for food trucks, concessions, and other operations where space is critical.

Finally, the largest food warmers are holding cabinets. These are available in under-counter, half, or full-sized configurations. They let you hold lots of food in a small footprint.

Just as there are different types of food warmers, there are also different technologies behind them.

Warmer Technologies

Dry warmers are just that. These drawers or cabinets, also known as “hot boxes,” use simple electrical heating elements to heat the unit interior. Because they don’t add moisture to the unit’s atmosphere, they can only hold for a short time before food quality starts to drop. Inevitably, food will start to lose its moisture. Not only does this dry the food out, but it also causes food temperature to drop (because evaporation is a cooling process).

Passive humidity warmers add a water bath to the unit’s interior. They are an improvement over dry warmers because the addition of a water bath means moisture isn’t being provided solely by the food itself. They are better than dry units but are less accurate than more sophisticated warmers.

Humidified warmers offer better temperature accuracy. Their internal water bath is temperature-controlled, which extends holding time.

The most accurate warmers are Winston’s CVap (controlled vapor) holding cabinets and warming drawers. CVap uses a dual-heat system of dry air heat and moist vapor heat. This means that CVap warmers precisely control food temperature and maintain the desired surface texture. CVap is equally effective at holding crisp or moist foods for extended times.

Rethermalizer vs. Warmer: Differences

As described previously, the biggest difference between rethermalizers and warmers is their function. Rethermalizers reheat or cook food. Food warmers do not. As mentioned before, you can hold food in a rethermalizer, but you cannot cook in a food warmer. Rethermalizers are designed for speed and require much more electrical power than warmers.

Rethermalizer vs Warmers: Similarities

Rethermalizers and warmers share some similarities. Many use some form of water or water vapor as the thermal medium to cook or hold food. Since water is efficient at heat transfer more energy is directed into the food than is wasted in the atmosphere.

Rethermalizer and warmers may have similar appearances. Although there may be some overlap in function, they serve different primary purposes.

Rethermalizing Prepared Foods in Bulk

Rethermalizing Prepared Foods

Retherming bulk packages of prepared foods can be challenging unless you have the right equipment. To clarify, let’s discuss rethermalizing, define prepared foods, and outline what operations are likely to use premade food. Finally, we’ll talk about what equipment is best suited to retherm them.

What is Rethermalizing?

Rethermalization is the process by which prepackaged food that is either frozen or chilled is brought to hot temperatures safely and effectively. Food must transition through the temperature danger zone (41°F to 135°F) in under two hours to meet the FDA Food Code. And although we’re primarily talking about commercially prepared foods, you can also use the retherming processes on leftovers. When reheating leftovers, food must reach 165°F in under two hours (though 90 minutes is preferred). (If you want to get down to the nitty-gritty, find specific requirements in Chapter 3 Section 403.11 – Reheating for Hot Holding – Subsection A – E (page 91) and Chart 4-B.)

Rethermalizing Prepared Foods

What are Prepared Foods?

Prepared foods encompass a wide range of food products. In the broadest sense, prepared food is food that is ready for consumption. It has been produced elsewhere and sold to the consumer (be that an individual or an organization). We’re speaking primarily of commercially prepared foods. These are foods that are mass-produced long before consumption. They come in a can, a chub, vacuum-seal, frozen, or other forms.

Rethermalizing Prepared Foods
Rethermalizing Prepared Foods
Rethermalizing Prepared Foods

Popular with operators, prepared foods decrease labor by outsourcing the initial food product. Portion control is made simple. And when rethermed properly, prepared foods are indistinguishable from made-to-order food.

Who Typically Serves Prepared Foods?

Although commercial foodservice primarily serves prepared foods, they are also popular in these foodservice segments:

B&I (Business and Industry)

Businesses that are not primarily foodservice operators but purchase foodservice items (such as corporate cafeterias).
It also includes government facilities.

Education

This includes preschools, K-12, colleges, and universities.

Healthcare

Another broad category. Includes hospitals, nursing homes, rehab facilities, senior living facilities, and others.

Concessions

Stadiums, museums, conference centers, amusement venues, country clubs, and others.

Catering

Also implemented at event facilities and mobile caterers.

These seem like widely disparate operations, but they have one thing in common.
They all need the ability to retherm large quantities of food quickly and safely.

Retherming Equipment

Achieve retherming by utilizing several different equipment pieces. The most common are rethermalizing ovens (a.k.a., thermalizersthermalizer ovensrethermalizersretherm ovens, and others).

Some folks may think first of combi ovens. Combis certainly can do the job and do it faster than most other oven types. But they also involve a substantial investment in upfront costs and operating costs. They require expensive vent hoods in most locations. A more economical option is the rethermalizing oven.

history why we build retherm ovens

In many respects, retherm ovens are like convection ovens or cook and hold ovens. However, retherm ovens have greater wattage and air movement. CVap Retherm Ovens also feature vapor heat. Consequently, this improves energy transfer efficiency. Retherm efficiency is the transfer of energy from a heated cabinet to a thermal mass (food) at a fast and controlled rate. In other words, retherm energy efficiency measures how much power an oven consumes and delivers to the food product during rethermalization. Since heated vapor is tremendously efficient at energy transfer, CVap retherm ovens excel at heating a thermal mass quickly.

Critically, the larger the thermal mass, the more energy (kW) is needed to transfer to the mass. Similarly, the more energy (kW), the faster the thermal mass can absorb the energy and reach desired temperatures. Consequently, this makes retherm ovens ideal for reheating chilled or frozen foods. They deliver lots of energy quickly.

Winston CVap Retherm Oven

Of course, Winston’s CVap® Retherm Oven is the hands-down best. CVap Retherm Ovens feature two circulation fans, providing robust air circulation throughout the oven. The fans speed up the retherming process and minimize hot or cold zones within the oven.

Winston-Foodservice-No-Vent-Hood

CVap ovens have a maximum air temperature of 350°F and can operate without a vent hood in most locations. Winston has conducted independent testing to verify. Hood availability is an important consideration when choosing an oven.

Another thing to consider when choosing a retherm oven is versatility. CVap Retherm ovens aren’t one-trick ponies. Yes, they’re great at retherming. But they can also bake, roast, sous vide, low-temp steam, and more. Whether serving prepared foods or cooking from scratch, CVap Retherm Ovens are the perfect oven for any large-volume feeder operation.

Cooking in the Kitchen with a CVap® RTV Retherm Oven

Chef Sam shows what RTV Retherm Ovens can do.

School Menu Items in a Retherm Oven

Watch as Chef Sam cook a variety of menu items in a retherm oven. CVap RTV Retherm Ovens are versatile. This video features some of the more popular school menu items, such as pizza, breakfast corndogs, and tater gems. Chef Sam also offers tips to get the best results.

You’ll also see how CVap ovens can utilize a probe for highly accurate cooking. Both thin and thick-cut pork chops and other proteins can be prepared in the same oven, with consistent results throughout.