When Bigger Isn’t Better

October 2001

When Bigger Isn’t Better

By Bruce Floyd
Contributing Editor

It’s very tempting to want to increase efficiency and make a system run faster using the same labor input. Sometimes the product quality actually improves when a system runs faster and/or the reaction time is reduced. However, other times this is not true. The pressure to run faster and cheaper, can create many problems, and any potential problems must be considered when evaluating proposed processing changes.

Most of us know that to prepare a meal for 240 people, taking a recipe for 4 and multiplying it by 60 doesn’t work. Too many things can change when using such a simplistic formula. Just consider the effect on the original cooking and cooling time.

Not a simple task
Food is a very complex biochemical system. Some food processes mirror chemical processing with the resultant material very close to a pure chemical, such as sugar. But many more are not. Many who evaluate food processes lack sufficient understanding of the underlying chemical and physical principals involved. Without an understanding of the fundamentals, it’s impossible to know which processes cause physical changes, which cause chemical changes and which cause both.

Several basic considerations should be looked at when increasing the throughput and/or changing the size of process equipment:
• Maintaining original product quality;
• Concentration;
• Time;
• Temperature;
• Mixability;
• Stability of each input above; and
• Added risk of loss.

A quality norm should be established that will serve as the basis for all comparisons. “Bad” can vary — just because today’s sample is better than the one made yesterday, that doesn’t make today’s sample “good.” Establish an objective system for evaluating production samples if one does not already exist and include sensory, visual and tactile evaluations.

Unfortunately, one possible result of faster and cheaper is a product that the consumer doesn’t want. An article in Food and Drug Marketing magazine several years ago, entitled “The Myth of the Product Life Cycle,” asserted that customers do not desert products; products desert their customers. When products become successful, they can be cost-reduced out of recognition. It is important to verify that the end result of any and all processing changes is a salable product that is still desired by the customer.

Accelerating the process
How are processes accelerated? By installing bigger and faster whatever.
There are several approaches: add more processors, halve the mixing time, increase the size of the processors or change the process. If space is available, the best option is to add more processors. There are disadvantages to this approach. There is no reduction in the direct cost of processing. (There are overhead savings.) It will require the same amount of space as the existing process. No one gets to look like a hero to upper management and it is too simple a solution to be recommended by most consultants.

Other options are to: add the ingredients faster; change the concentration; change the mixer size, speed or type; or discharge the batch sooner. Many times, all of these are done simultaneously. But there are issues involved. Why did the original process parameters exist? Is product sitting in tanks because processing isn’t balanced with the packaging line? Or, is the problem not with processing at all?

I worked with an engineer on a project to increase blending speed. However, I discovered that the problem was not with the blending system, but with the bagging operation. The system filled totes at a rate of 24,000 lbs. per shift, but only 13,000 lbs. per shift into bags. If the blending process were sped up, would the bagging operation have been any faster? This seems obvious, but for some people, it is beyond their perspective.

In some cases, the problem is not with processing, but rather with supplying processing. If it takes 20 minutes to feed a blender and only 10 minutes to mix, then the feed time needs to be reduced. How many times are systems designed to run a certain rate per hour? Each single component runs the same speed. Unless it is a continuous system, there are bound to be problems.

Concentration concerns
In liquid systems, simply changing the concentration can accelerate the process. However, concentration affects both chemical and physical properties. Take chemical addition. If there is a chemical reaction, is it concentration-sensitive? By increasing the concentration of the added chemical, the localized concentration at the point of addition will be much higher. What will this do to the molecules of product that are in that area of high concentration? Now change the speed of addition. Will the change be accelerated? Speed up the agitation, then what happens?

Concentration affects the physical properties as well. Solubility is concentration-dependent. It is easy to suspend ingredients without having them go into solution. In many wet processes, the ingredients do not completely dissolve; however, the mixing equipment is strong enough to cover up the problem. There is a critical concentration for each ingredient. At times, the order of addition of each ingredient is important. Some ingredients compete for free water better than others. Some materials bind water and make it unavailable to others. Water solubility for chemicals is listed in the “Handbook of Chemistry and Physics,” but for food products, it may have to be experimentally determined.

Controlling the process
Many products are held too long, too hot. The natural conclusion is to assume that all products are being held too long. Just as there are critical concentrations for solubility, there are critical reaction times. The rule of thumb is that for every 10°C change in temperature, the reaction rate doubles. If heat causes unwanted changes in a product, running at higher temperatures may not be an option for increasing a production rate. Caution: Do not forget public-safety issues when considering changes in process temperature and production rate. Sometimes a product is held too hot, too long for a reason — to kill bacteria.

At the bench or stovetop level, there is a tendency to underestimate the energy available to the product developer. Mixing in the lab cannot always be duplicated in the plant. I have a small 1/16 horsepower lab mixer which does a better job in a 1,000-ml beaker than I could ever hope for in a 1,000-gal. reactor. If the goal is to double the amount of product being mixed in a given amount of time, the mixability of the product must be considered. A much better process will result if the goal is pursued methodically. For example, what will increased energy (mixing) do to the product? The difference between a magnetic stirrer and a Waring blender is energy input and shear. If it makes no difference to the final product which is used, this becomes a moot point. With dry mixing, how will this be done? What happens to the product when mixed faster? Does it liquefy, melt, segregate or break down?

Big trouble
One method to increase production is to increase the size of everything. If making 2,000-lb. batches, increase that to 4,000 lbs. or 6,000 lbs. by installing new equipment that is bigger and faster. This may affect how well the product is mixed. For example, to go from two 2,000-lb. batches per hour to two 6,000-lb. batches per hour, everything will have to move through the system three times faster. Batching into a continuous system uses the same principle.

There can be problems with scale up. Certain things do not scale up by a linear multiple. What is the tank geometry? What is the new surface area-to-volume ratio? This affects heat transfer and friction. What is the new rate of agitation? How much horsepower will be required? Is the mixing efficiency the same? Are the sheer forces on the product the same? What about turbulence and air incorporation? If this is a cooking operation, is it possible to accommodate three times the volume without physically or chemically changing the final product? How will the new process be controlled?

One of the fictions of running faster is that the sample rate will be the same per hour. Sample rate should always be determined by the stability of the system.

Size does matter
Equipment size affects how materials — wet or dry — will flow in and out. If there is a tendency for products to separate, this will become an everyday challenge in larger equipment. Products can stratify in storage tanks. The added weight on the bottom of bins leads to product compaction and discharge problems.

Throughput affects the system’s stability. If using a scale that is ±1% accurate at a 2,000-lb. batch size and it changes to ±2% at a 6,000-lb. batch size, the actual variation changes from ±20 lbs. to ±120 lbs. per batch. Can one buy the larger scale with the same sensitivity?

Remember that readability and accuracy are not the same thing. This follows for each and every control device. Is accuracy being sacrificed? One could still have the same mean, but a much larger variation within each lot resulting in unexplained quality variations. With continuous equipment, the idea is to push more product through the same equipment or install bigger equipment. Either way, the forces acting on the product have to change.

When running more product in a shift, the chances of larger losses from production mistakes increases. If a process involves many different ingredient additions, then making fewer batches should reduce the frequency of mistakes. A new system increasing from 2,000 lbs. to 6,000 lbs. would have to reduce the error rate by more than three-fold to be a better option. A better plan is to fix the current problem.

In terms of daily production, plants have gone from 20,000 lbs. per lot to as much as 200,000 lbs. per lot. Just how much product do you want to put at risk? This is not a HACCP risk evaluation. Is your QC system up to the increased risk of faster production? What will it take to make it equal to the job? This is a good time to install in-process control procedures if you do not already have them. To make sure that a plant is not hiding rework in inventory, it is a good idea to send people familiar with the product and process along with the accountants to take inventory.

No one wants to stifle progress. Conversely, no one wants to stand by and see good products changed irretrievably, either. Some of the problems I have witnessed have been the result of faulty accounting systems. Short-term results were all that were considered. Other problems are tunnel vision and the idea that anyone questioning the system is not a team player. There is sometimes a rush to agreement when an attractive idea is presented, but it is important to thoroughly evaluate each option. This includes shelf-life testing, which is often skipped.

The key step lies with the people responsible for evaluating the process change. The quality of their work could make or break the company.

Bruce Floyd established Process Systems Consulting, Iowa City, IA, after working more than 30 years in the food processing industry. He has had extensive experience in sanitation, quality control, regulatory relations, and product and process development (both domestic and international), and specializes in integrating ingredient selection and manufacturing into a total processing system. A graduate of Georgia State University, he has successfully completed all areas of the Better Process Control School at the University of Minnesota, and has been qualified by the International HACCP Alliance as an instructor. He can be reached via e-mail at [email protected].

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