Oil Uptake in French Fries
Table 1 : Batter coating formulation Ingredient
Brand Corn Starch
Rice Flour Salt
Methyl cellulose Water
HYLON VII corn starch
Ener-G gluten-free white rice flour
Morton’s iodized
WELLENCE™ SmartFry 900
Tap water at 4°C
Amount (wt%) 10.3
13.0 0.8
1.0 75.0
increased temperature. Therefore it can be applied as a thin, low-viscosity batter that, when heated, forms a gel [ 9 ]. The gelled formulation inhibits oil entering the food, reducing fat uptake generally by more than 30% [ 10 , 11 ]. The batter can even have the added benefit of reducing some of the water loss from the food, leading to a moister product. Batters can also decrease heat transfer coefficients, which have also been correlated to decreased fat uptake [ 12 ]. Whether incorpo- rated into batters currently used on the food, or applied as a thin topcoat over an existing breading or directly onto unbattered food, these coatings do not negatively impact flavor or texture profiles of fried food.
The impact of fat reduction strategies can be measured by bulk analysis techniques such as Soxhlet extraction. However, information about the spatial distribution of oil within the fried foods is harder to come by. Nuclear magnetic resonance imaging [ 13 ] and X-ray imaging using radiolabeled 14 C palmitic acid [ 14 ] have been applied to visualize the fat distribution across cross sections of French fries. However, these techniques are not readily available, moreover they are slow and expensive. Confocal microscopy has been applied, using fluorescence-labeled oil to visualize its location at the pore and cellular level [ 15 ]; the special oil required for this method negates the ability to apply it to commercially available fried food. The purpose of our investigation was to develop a practical method (relatively fast and readily available) to characterize the distribution of oil across entire pieces of fried food.
Materials and Methods Materials . Russet potatoes and salt were purchased from a local market in Midland, MI. Rice fl our was purchased from Ener-G; corn starch
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was purchased from National Starch. WELLENCE™ Smart Fry 900 was acquired from Dow Chemical. Preparation of potato strips . Potatoes were hand-peeled, with both ends cut off. Those potatoes were cut into strips with the cross section of 3/8 inch × 3/8 inch, and uniform pieces were chosen for experiments. The strips were rinsed with water and then blanched in water at 85°C for 7 min. After blanching, the potato strips were immersed in 0.2% citric acid solution at 95°C for 1 min. Then, all pieces were drained and dried in a conventional oven until ~10% weight loss was achieved. Batter coating . Batters were prepared by dry blending rice
fl our, corn starch, WELLENCE™ Smart Fry, and salt in a mixing bowl (Kitchen Aid) with a wire whisk attachment according to Table 1 . Water was then added to the dry ingredients, and the mixture was blended at medium to high speed for about 30 seconds. T e mixture from the side of the mixing bowl was scraped down and blended for another 30 seconds, aſt er which the mixture was blended for an additional 8 minutes at a lower speed (slow to medium-slow). T e batter was then transferred to a mixing bowl and mixed with 200 g of room-temperature prepared potato strips for about 15 seconds using a spatula. Batter-coated potato strips were placed onto a wire rack, turning 1–2 times to enable excess batter to drain.
Figure 2 : Depth of oil uptake. (a) Image of stained uncoated fry. (b) Image of stained coated fry. (c) Binary threshold image of uncoated fry. (d) Binary threshold image of coated fry.
www.microscopy-today.com • 2018 January
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