Kettle Style Chips
What are Kettle-Style Chips?
Kettle-style chips are produced by direct slicing the potato into the fryer. The potatoes are, therefore, not rinsed as those produced in continuous fryers. The products are called kettle, a trademarked term, or kettle-style chips because they are fried in a kettle. In other words, it is a batch process. Kettle-style chips have a crisper “bite” and may appear thicker and crispier to the average consumer. The fact that they are not rinsed prior to frying contributes to these unique and highly desirable characteristics.
In commercial production of kettle-style chips, the potatoes are fried at temperatures of between 310 – 320 oF (155 – 160degC) until they meet the desired quality parameters, which includes oil pickup. Kettle-style chips generally contain 30 – 35% fat. During the frying process, the temperature of the fryer drops to approximately 290oF (143degC). Frying time is approximately 5 – 6 minutes. Paddles moving up and down the kettle ensure even frying. At the end of the process, the chips are “raked” from the fryer, and the fryer is allowed to recover at which time the next batch of potatoes are sliced into the fryer. The whole process cycle takes approximately 10 – 12 minutes.
Challenges with Kettle-Style Chips
There are some distinct challenges inherent in the production of kettle-style chips. Since the chips are produced by direct slicing the potato into the fryer, a significant amount of starch is washed off in the frying oil. This water-soluble starch is cooked in the oil and is modified by the oil so it becomes the same density. Therefore, this soluble starch cannot be removed from the oil by a centrifugal type of separator. These starches will also blind the surface of the filter modules effectively reducing their life.
There is also a significant potential for heat damage to the oil with kettle chips because of cycling between batches. Any time that heat is pumped into cooking oil it can damage the oil. In fact, Perkins and Van Akkeren (1965) clearly demonstrated that subjected frying oils to temperature fluctuations was more damaging to oil than maintaining that oil at a constant temperature. These studies were carried out in foodservice fryers, but when one thinks about it, a fryer for kettle-style chips is really a large foodservice system.
Although the kettle-style chips absorb between 30 – 35% of the frying oil, that is slightly lower than what happens to chips produced in a continuous system. The turnover time for the oil will not be quite as one would see in a continuous system. In addition, since the kettle fryer is a batch system, there is a greater potential for accumulation of solids and metals from the foods being fried. In fact, Filtercorp has collected data from kettle fryers that indicate that soaps and metals will accumulate more quickly in batch systems compared to continuous systems. Soaps and metals in oil will compromise both useable oil life and the shelf life of finished products.
In commercial production of kettle-style chips, manufacturers monitor free fatty acid levels in the cooking oil. The end point utilized by kettle-style chip manufacturers is 0.5 – 0.6%. Given the challenges cited above, kettle-style chip operators often do not achieve the oil life that they would like to have.
Enhancing Kettle-Style Chip Frying Oil Quality
As noted above, Filtercorp has been involved with kettle-style chips for many years. Over 20 years ago, the company worked with a kettle-style operator that had experienced a problem with reduced shelf life. Laboratory analysis of oil from the fryers indicated that there were elevated levels of soaps in the oil. The company installed Filtercorp’s FM1 unit with Supersorb® pads.
This system significantly reduced soaps in the oil and eliminated the shelf life issues.
According to Robertson (1967), maintaining the quality of frying oils and fried food is a function of the following;
- Design, construction & maintenance of equipment
- Proper operation of equipment
- Properly cleaning of equipment
- Minimize exposure to UV
- Keep salt & metals away from oil
- Filter regularly
If a company is doing all of the above, the only real option for enhancing overall oil quality is to look at oil filtration or treatment. Filtercorp has already shown that treatment with Supersorb® filter and treatment media can remove metals and soaps, plus enhance product shelf life. And, this was accomplished with a first generation system. We also know that utilization of the 3rd generation FM3 filter and treatment unit in kettle-style fryers will slow the rate of free fatty acid formation.
Perkins, E.G. and Van Akkeren, L.A., (1965), “Heated fats. IV. Chemical changes in fats subjected to deep fat frying processes: Cottonseed oil,” JAOCS, Volume 42, Issue 9 , pp 782-786
Robertson (1967), “The Practice of Deep-Fat Frying,” Food Technol.21:1, 34-38
We feel that the overall benefits treating oils used for processing kettle-style chips are;
- Improved shelf life and product quality.
- Improved temperature recovery time, better efficiency.
- Reduced overheating of oil in contact with heating elements (reduced oil thermal degradation).