Potato chips moisture content

Figure 11.5 SEM images of the surface of control (a) and petroleum ether washed control for one second after frying (b) potato chips (moisture content 1.8%, total basis) fried at (1) 120°C (2) 150°C (3) 180°C (reprinted with permission from). Food Eng., 2008, 87, 200-212).

FIG. 17 Water activity (or relative vapor pressure) and moisture content (%, wb) values plotted for a variety of food materials ( as is ), resulting in a composite (or universal) food isotherm. Potato chip and nonfat dry milk (NFDM) data are from van den Berg (1986). All other data are from the author s laboratory (at 20 or 25 1 °C). Water activity and moisture content values for the breakfast cereal and fruit and vegetable categories had the largest ranges (expressed here as standard deviation) 0.311 0.073 aw and 2.94 1.55% me (wb) and 0.995 0.004 aw and 89.8 3.90% me (wb), respectively. The curve is to guide the eye—it is not a fitted line. 

Potato chips are partially dehydrated in the fryer (moisture content 8-12%). 

As one can see, these numbers vary greatly with the type of product. Potato chips require the highest amount of heat energy because of the high moisture content of the raw potatoes (around 80% moisture). 

Most low-moisture cereal-based foods (e.g., biscuits, extruded products, potato chips, etc.) have a crunchy or crisp texture that is lost as the moisture content increases either by redistribution within the product or moisture pick-up from the environment. The loss of crispness of cereal products and... 

Potato chips are fried to a final moisture level of 3% or less, which accounts to an of about 0.2. Tortilla chips, corn chips, and other snacks have a final moisture content of <3%. From a study on potato chips a moisture content of 3.57% was the point at which a taste panel rejected the chips because of their texture deterioration [39]. Moisture absorption and the consequent deteriorative changes can be prevented by the use of packaging materials with appropriate moisture barrier properties. In this case the shelf life of the products can be extended to several months. If the packaging material is not transmitted by light and if the air inside the packaging is replaced by an inert gas, e.g., nitrogen, a considerably longer shelf life can be obtained. 

Dehydration is performed in a conveyor or tube dryer at 55-60 °C to a residual moisture content of 4-8%. Liquid or paste forms, such as tomato or potato mash, are dried in a spray or drum dryer or, in the case of some special products, in a fluidized bed dryer. Dehydration by freeze-drying provides high quality products (good shape retention) with a spongy and porous structure that is readily rehydrated. Some vegetables used in soup powders, e. g., peas and cauliflower, are prepared in this way. For production of dehydrated potato products (Fig. 17.4), tubers are peeled, cleaned, sliced into strings or chips or diced and, after... 

C. subvermispora strain LI4807 SS-3 (Cs SS-3) was obtained from the USDA Forest Service, Forest Products Laboratory (FPL) in Madison WI. All stock culture slants were incubated at 26°C, stored at 4 C, and maintained at 2% (w/v) potato dextrose sugar plates. The samples were prepared and maintained as reported in Bartholomew (25). When needed for treatment, 2.31 ml of mycelium was added to 100 ml of sterile water and blended for 75 seconds. The blending was done in 15-second intervals followed by a 15-second pause to avoid heat build up, up to a total of 75 seconds of blending. The blended mycelium was transferred to a sterile beaker, additional makeup water was added directly to the chips to yield a 55% moisture content, and 0.5 % unsterilized corn steep liquor at 50% solids added to the beaker. The mixture was then poured over the chips in the bioreactor. 

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