The humble potato chips, liked universally by the old and the young alike and made in almost all the countries in the world, can boast of an origin back in 1853 and the popular snack has never looked back since then. It took almost 100 years for the chips to be made with seasonings and to day there are a number of flavored versions in the markets of different countries depending on the preferences of the consumers there. Though making any fried product appears to be a relatively easy job, making chips from potato has many nuances, evolved over the last 160 years. Called Chips in many countries, the same product goes under a different name in the UK and Ireland where it is known as crisps. If the fried product in slice form can be referred to as chips, there are similar products made from sweet potatoes, mainly in Korea and Japan, from Parsnips, Beetroot and Carrots in the UK and from Plantain, Cassava, Yam in India. Some varieties of Plantain are processed into chips in the American Hemisphere and are marketed under the names Chifles or Tostones. A new breed of potato based products made by mashing, extrusion and frying are gaining popularity lately and these products are referred in the US as crisps. Potato sticks refer to products made by cutting the raw material into thin stick form before frying. Sticks are made from Cassava also in some countries.
Frying is a simple process but the science involved is not as simple as being imagined. The eating quality of the fried product depends to a large extent, on the variety of potato used, pre-processing steps, nature of frying oil, ratio of oil to the material fried, temperature of the frying oil and duration of cooking. Traditionally in India during the potato season when the prices are very low, many house holds buy them in large quantities to process into sun-dried slices for making fried chips through out the year. Though the product so made has crisp texture, it cannot be compared to the modern commercially made fresh chips in eating quality. But it still serves a purpose in that farmers and consumers have at their disposal a technique that can preserve potatoes for a few months under ambient conditions without spoilage. One of the most studied aspects of frying is the undesirable changes taking place in the oil at temperatures in the range of 160C-200C commonly used by the manufacturers, causing thermal damage and repeated use of such oils can even make the product unsafe for consumption. Oxidation, pyrolysis, polymerization and interactions amongst the artifacts change the characteristics of the oil irreversibly calling for utmost caution in managing frying operations. Incorporation of antioxidants like BHA, TBHQ, Propyl Gallate etc can retard oxidation of oil during frying. Fry Powder, a proprietary frying aid based on diatomaceous earth, used by many chips makers, is known to prevent formation of polar compounds during frying enhancing product quality and shelf life while reducing oil absorption during frying.
The tendency for potato slices to change color when exposed to air was one of the early technological challenges for the industry which was found to be due to chemical reaction between sugar and free amino acids present in the potato. While blanching in hot water can inactivate the enzyme system, chemical reaction can be pre-empted only if suitable varieties with low glucose content are used as raw material. Cold stored potatoes, available all year round, cannot be used immediately for chip making as they have high accumulated tissue glucose which has to be brought down by "curing" at ambient temperature for some time. Similarly potatoes with higher specific gravity ( more than 1.1), generally the typical feature of a mature crop, can reduce oil content very significantly during frying compared to those with lower specific gravity. Generally raw materials with dry matter content beyond 24% gives a low oil containing fried chips while during the preparation thinner the slice higher will be the oil uptake. Pre-gelatinization before frying proper also can bring down oil absorption by the product during processing.
Old traditional process of making potato chips was invariably batch type with small quantities fried in a kettle and process control aspects were never given much attention. By experience and skill developed over a long period, artisan entrepreneurs made kettle cooked chips which were much superior to that made by modern day continuous processes and this led to demand by the market for similar chips. The innovation in slicing whereby, in stead of straight slices, corrugated type of slices with greater thickness, gave more crispier and better crunchy product which more or less compared well with kettle cooked chips. But kettle cooked chips still scored over all other versions and many large scale manufacturers sensing the market demand started making chips with eating quality similar to kettle cooked chips with the result there are many reputed brands of such chips in the market. There are many techniques that can achieve the quality desired and slow cooking at lower temperatures invariably gave a better textured product. In some processes two stage frying is adopted where the slices are fried at low temperature first, followed by cooing and removal of the adhering oil before the second frying at a higher temperature. Probably during the first frying, only gelatinization of potato starch takes place while second frying imparts color and the typical taste. Oil content in kettle cooked chips is always less to the extent of 15-20% probably due to the pre-gelatinization taking place during the initial slow frying period. Even the crunchy taste typical of kettle cooked chips can be attributed to this subtle difference in frying process. Though kettle cooked chips give the impression that they are hand made, industrial scale manufacture is managed with high capacity continuous automated plants.