Production Tech: 'Hot' topic
Environmental awareness in the food industry has become increasingly important in recent years as a result of consumer pressure and increasing regulation. Just how can the industry achieve environmentally friendly food production, in what ways can it improve operations and become more environmentally responsible?
Consumer pressure and increased regulation also have made environmental awareness more important in the food industry. Now more than ever, it is essential for food manufacturers to understand the environmental impact of their activities and raise their production standards.
In an ideal world, the amount of fuel converted into energy to heat a process would be totally applied to a product, whether it’s baking bread, frying chicken or drying jerky. Unfortunately, the world isn’t perfect, and energy losses abound in thermal processes. Although conserving energy may be politically correct or “green,” most processors’ reasons for saving energy are not so altruistic. Putting more energy into the product and less into the environment cuts operating costs and directly improves the bottom line.
“The meat and poultry industry is riddled with opportunities to make use of wasted heat,” says Jason Perry, research engineer for the University of Georgia’s Engineering Outreach Service. “Any time you are allowing heat to escape from the atmosphere you are losing energy.”
Technology improvements in ovens, dryers, fryers and heat exchangers lately have been key to improving product consistency and saving energy. Many of the tools required to save energy, however, are the same tools that help processors perfect their product and minimize scrap.
When a processor looks for thermal equipment, product quality is said to be the No. 1 consideration. Selection criteria is often based on final moisture control, energy savings (including reclaiming heat from the product), cost and minimum footprint. Product yields are always at the forefront for protein producers, but making sure the product is fully cooked and safe is the critical issue.
Therein lies the rub. A given product will require a specific number of BTUs to be fully cooked, so the key to gaining energy efficiency is to make sure the BTUs put into an oven or fryer are distributed evenly and used fully. If processors have an oven or a fryer that applies the heat uniformly to the product, for example, they can cook faster and use less energy because they don’t have to slow down cook time to ensure all products are fully cooked. An oven or fryer that cannot uniformly distribute the heat adds to energy usage.
If the oven is balanced and uniform with heat coverage, the process is faster, product is more consistent, and in the long term, the process uses less energy.
Additional methods to save energy in ovens include a more efficient fan drive and an air-handling system that reduces resistance, thereby reducing horsepower requirements. Though not as critical to overall energy usage in ovens, motor efficiency concerns some manufacturers to the extent that they are actually specifying premium-efficiency motors over high-efficiency types, and they’re also taking another look at high-efficiency burners.
Every burner wants to have a little excess air. Maintaining that excess air ratio can maximize the efficiency of the burner. Burner-ratio control systems can maintain the ratio and provide a 2- to 4-percent increase in efficiency. Another way to improve the efficiency of the burner is to preheat the combustion air. This heat can be reclaimed from locations where heat is lost in the system, for example, in the stack. Preheating the combustion air up to 250 to 300 F, and sometimes as high as 500 F, can provide another burner efficiency improvement from 4 to 6 percent.
Equipment analysisFood processors consider new-generation cooking and frying systems: higher throughput and yield are appealing possibilities. But if taste, texture, color or appearance is affected, the outcome is dismal.
Products that reflect changing tastes, serve convenience demands and can help stake out a healthier-eating claim require production lines with greater flexibility. The challenge for suppliers is to leverage the principles of heat transfer to engineer systems that can produce new items while still doing justice to the old.
Nowhere is this more evident than with contemporary ovens. Heat-and-serve meat and poultry products are enjoying substantial growth, spurring continuous innovation in the pilot plants of equipment suppliers. Researchers at University of California-Davis utilized computational fluid dynamics (CFD) in designing new spiral ovens with circular enclosures. Dead zones in square configurations were eliminated with a 360-degree airflow system that delivers uniform steam or dry heat across each stack.
Uniform heat means greater yield, though spiral ovens can’t match the throughput and browning capabilities of an impingement oven. Some suppliers are introducing the best of both worlds, hybrids that combine the spiral oven with an optional impingement zone on the back end.
Multiple heat-transfer mechanisms play out in the combination oven. Researchers have documented yield improvements of 2 percent for bone-in chicken wings and 4 percent for boneless chicken breast, but the ability to achieve many different effects is the combo unit’s real strength. The spiral stack area is equipped with a “dynamic airflow control” to manipulate dew-point temperatures on the product surface by reversing airflow at critical times.
Typically, incoming product is blasted with steam, which has a high heat-transfer rate. Convection heating takes over when the surface temperature dips below the dew point of the surrounding environment. By reversing the airflow at that point, it’s possible to extend condensation heat transfer, which is the best cooking method. It is said that immediate transfer to the impingement zone minimizes temperature loss on product surface.
When it comes to fryers, continuous filtration is a must. Some of the market’s double-filtration systems support such fryers. Continuous filtration can reduce oil use by 35 percent.
Used in conjunction with magnesium silicate to encapsulate free fatty acids, researchers have shown that advanced filtration can dramatically cut down the amount of oil waste from a food fryer. The other key factor impacting oil maintenance is the turnover rate â€” the operating time in which all the system’s oil would be absorbed if no replenishment was done.
Note: Information excerpted from Tech Update: Cooking and Frying, Food Engineering Magazine, May 2007; and Tech Update: Thermal Processing, Food Engineering Magazine, October 2008. For full articles, visit www.foodengineeringmag.com.