GRACE – Processing & Packaging post will highlight the major steps involved in preparing and processing a raw potato into a delicious snack, the steps involved in frying a sliced raw potato, seasoning, and packaging a potato chip.
Potato chips are consistently a top seller in the highly competitive snack food market. To maintain popularity, manufacturers have developed a wide variety of flavors and styles. The manufacturing process, however, is fairly similar between them and manufacturers generally seek common objectives: a finished product with no defects, crumbs, or blisters and with a good appearance and a bright color.
Making potato chips begins with the raw potato and ends with the final packaged product. This post covers all the processes, from selecting the raw potato and washing to peeling to slicing, blanching to frying, after frying to seasoning and packaging.
Frying In Oil
Frying time and temperature will vary depending on a variety of potato, specific gravity, slice thickness, and possible sugar content reduction. These two parameters of frying are not constant and must be adjusted to produce uniform-quality chips. Generally, a higher temperature translates to a shorter frying time and less oil absorption. An excessively high temperature will result in burnt or caramelized chips and quicker oil breakdown.
The steam released from the potatoes forms a blanket of non-oxidizing gas over the oil. This furnishes the steam blanket as well as provides a continuous deodorization of the oil. A positive effect is that undesirable products do not accumulate because of a rapid turnover of oil, a result of constant replenishment with fresh oil to compensate for what is absorbed by the chips. A negative effect of water vaporization is that antioxidants, such as butylated hydroxytoluene (BHT), are steam-distilled out of the oil. BHT delays rancidity and flavor deterioration in potato chips.
Specially designed equipment can be provided to increase the temperature of the chips after they emerge from the fryer and provide a significant reduction in oil content. As steam is being rapidly released from the slices, oil absorption will be low. As the protective layer of water vapor begins to disperse in the final stages of frying, fat enters the voids left in the dehydrated cells.
Factors Leading to Oil Deterioration
Hydrolysis
This occurs when chemical bonds holding triglycerides together are broken by water, creating free acids. Frying systems with high oil turnover rates usually maintain acceptable oil quality and the steam realized tends to strip free fatty acids (FFA) from the oil.
Oxidation
The primary reaction is the formation of hydroperoxides. Higher numbers of double bonds in the unsaturated oil will increase the rate of oxidation. This reaction is enhanced by heavy ions. Copper is a potent oxidation catalyst, and its use must be avoided. No copper fittings or brazing should be used in frying equipment.
Polymerization
The two major types that occur are:
1. Oxidative polymerization–free radicals are formed when hydroperoxides decompose at high temperatures and combine, doubling the weight of the triglyceride. Eventually, as the molecular weight increases, they are no longer soluble in oil and will be deposited on the fryer wall.
2. Thermal polymerization–primarily occurs at hot spots on the frying equipment, caused by localized overheating.
The oil used for frying has two functions:
1. It serves as a medium for transferring heat from a thermal source to potato slices.
2. It becomes an ingredient of the finished product.
Some of the factors affecting the amount of oil absorbed by the potato slice are:
The solids content of the potato
Oil temperature
Duration of frying time
Thickness of slices
Variety of potato
Condition of potato
Slicer operation
Conditioning
Type of slice (wavy or flat)
Relationship of FFA with Smoke Point of Frying Oils
FFA increases during frying, due to a reaction between the oil and the water released by frying. FFA will rise and should be maintained below 0.5%. This reaction causes the oxygen to react with the double bonds in the unsaturated FFA. Their values above 0.5% will detrimentally affect the quality and shelf life of the processed food. Initially, peroxides are formed, which in turn break down to ketones and aldehydes. The peroxide value may be helpful in measuring the degree of oxidative rancidity in the oil.
The smoke point is the temperature indicated when the oil gives off a thin, continuous stream of bluish smoke. The smoke point of the oil is an excellent indicator of fresh oil quality. Good oils (as received) will have a smoke point of well over 482°F (250°C). As the oil is used the smoke point will be proportionally reduced.
Packaging
After the potatoes have been inspected, they are ready for the final stage of the process: packaging. The size of the potatoes used for chips will vary depending on the final size of the package into which the chips will be packed. Small potatoes are desirable for small bags, while large potatoes are usually desirable for larger-sized packages.
Packaging must be tested for water vapor and oxygen transfer rate, greased resistance, odor permeability, taste permeability, and ink and coating adherence. Each load of file should be checked by the supplier and/or the customer through visual examination for physical damage (e.g., pinholes, rips) and misprinted graphics. The stock should be limited to a three-month supply as the film deteriorates as it ages.
The packaging lines should be continually checked to ensure correct fill, net weight, breakage elimination, proper seal, designated code, and proper expiration date.
If the frying oil is stabilized, the packaging film is opaque, and has a low moisture vapor transmittance rate, a shelf life of 4–6 weeks should be achieved when chips are stored at temperatures of approximately 70° F (21°C). The use of opaque packaging prevents light from being transmitted through the film, preventing accelerated oxidation of the potato chips.
Once potato chips are in the bag, three forms of quality degeneration will have the greatest effect on consumer acceptance:
Breakage: This can be partially prevented by using stiff packaging material and making the package “plump” with contained air, cushioning the product inside when the package comes between other objects.
Absorption of moisture causing loss of crispness: this is largely prevented by the choice of packaging material. The film needs to have a high degree of resistance to moisture vapor transfer. The film needs to have a high degree of resistance to moisture vapor transfer. Foil-containing film is preferred because it not only resists moisture-vapor transfer but also reflects light. Potato chips are commercially unacceptable when they have a moisture content above 3%.
Fat oxidation leads to the development of rancid odors: light and normal fluctuations in environmental temperatures affect the rate of oxidation. Sunlight has a strong accelerating effect on rancidity developments.
Snack manufacturers need the ability for quick changeovers to accommodate the different sizes of packaging needed to meet consumer demand. Final packaging starts with versatile packaging systems capable of running a variety of bag sizes, speeds, and bag formats. If the packaging line is sized correctly to leverage the bag mix, then it is simply a matter of scheduling the department to meet demands. It is important to have maximum flexibility by leveraging technologies such as on-machine seasoning, product sizing, and automation where it makes sense. Small bag capacity has certainly become a challenge for snack manufacturers; it is a constant challenge to balance the line and to ensure order attainment while trying to maximize processing capability.
In order to streamline changeovers, snack manufacturers employ different approaches depending on budgets, existing equipment, and processing goals. In general, the constants are ease of jaw or former change on VFFS, ease of sanitation for the complete line, and ease of machine operation. Snack manufacturers can further enhance this process with technology, such as auto splice for packaging and toolless changeover for automation.
In most snack food plants, the largest labor requirements are in the packaging room. The best way to reduce or to reallocate labor is to add automation. An automatic case packer can replace the functions of manually erecting, loading, inspecting, closing, and labeling a case. Depending on the line size, this could significantly reduce labor requirements, add packaging capacity, and leverage processing capacity. All of this provides a significant ROI and helps alleviate some of the issues related to a labor shortage.
