No abstract

An Instron punch test with three point support of a potato chip was developed, and factors affecting the results were evaluated. Individual potato chips were fried in palm oil in a forced circulation glass container, and their moisture content and texture were determined. Sample handling parameters contributing most to variability of moisture and texture were the cutting device, and position of the sample within the tuber. For oil temperatures 140 and 180ЊC, and two potato specific gravities, moisture and texture changes were studied during frying. Maximum force of break was in the 2-4% moisture region. Individual chips showed highly variable room temperature adsorption/desorption.

The instrumental and sensory analysis of the texture and color of commercial potato chips were compared. The instrumental measurement was a puncture test with an Intron Universal Testing Machine, and the parameters used were fracture force, deformation and stiffness. The instrumental color quantification was a computerized video image analysis technique, and the color was expressed as L*a*b* values. Sensory evaluation of texture and color was performed by a sensory panel especially trained in evaluating potato chips. The sensory attributes were “hardness”, “chewiness”, “crunchiness”, and “tenderness” for texture analysis, and “yellow color”, “burnt aspect”, “sugar colored aspect” and “transparency” for color analysis. The factor analysis of the sensory attributes indicated that texture can be divided into two principal components, one represented by “hardness”, “crunchiness” and “chewiness”, and the other by “tenderness” alone. The factor analysis of the color can be divided into two principal components, one including “yellow color” and “burnt aspect”, and the other “sugar colored aspect” and “transparency”. Discriminant analysis showed that “tenderness” and “crunchiness” could predict correctly over 90% of the data. Fracture force correlated well with all of the sensory attributes (R2 > 0.76), and L* with the sensory color attributes (R2 > 0.79). The “Tenderness” was the individual sensory attribute which had the highest correlation (R2= 0.95) with fracture force.

A simple method is proposed to quantify volume of potato chips by measuring the displaced volume of a finely granular material (rape seeds) by the volume of the chips. Firstly, compaction of the seeds was studied to evaluate the reproducibility and accuracy of the technique. The results obtained indicate an encouraging potential of the technique to estimate the apparent volume of potato chips and give some indications of variation of chip apparent density with some important technological parameters such as chip thickness, frying temperature, and pretreatment of the slices before frying (e.g., blanching). This technique showed that the apparent volume of un-blanched potato slices increased clearly (P ¼ 0.007) with frying temperature (from 120 C to 190 C) until the chips reached final moisture contents <3% (wet basis). For 180 and 190 C, the final apparent volume of these samples indicated that the chips expanded in $6% beyond its original volume before frying (14.1 mL). For potato slices blanched in hot water (80 C and 3.5 min) and fried under the same temperature intervals and conditions, this trend was not statistically significant (P ¼ 0.088), and the average apparent volume of the chips was 10.9 mL which correspond as an average to a shrinkage of $23%.

Texture of potatoes with different shapes (slices and strips) were evaluated after frying and in some cases after baking. Blanched and unblanched potato slices (Bintje variety) were fried at four oil temperatures: 160, 170, 180 and 190C until reaching a moisture content of ∼1.7%. A puncture test with three point support for the slices was applied to measure the texture of potato chips using the following parameters extracted from the force versus distance curves: maximum force of break (MFB) and deformation of break (DB). These two parameters were useful to follow the changes in texture of the fried slices with moisture content at different frying temperatures. Blanched and unblanched potato strips were partially fried at 160C and 190C for 60, 90 and 120 s. The par‐fried potatoes were frozen at ‐20C for one day after which they were baked at 200C for 15 min. The texture of the baked potato strips was evaluated using a bending test with two support points. From the force versus distance curves, two parameters were extracted: maximum force of deformation (MFD) and maximum deformation (MD). Significant higher MFB and lower DB values (P > 0.1) for unblanched fried slices indicate that these are crispier than blanched chips for moisture contents lower than 4% (6.59 N and 0.62 mm vs 5.74 N and vs 0.75 mm for unblanched and blanched chips, respectively, average values for the four frying temperatures employed). There was no effect of the frying temperature and the pretreatment (blanching or unblanching) on the texture of the frozen par‐fried potatoes after baking when compared at the same residual moisture content, but blanched potato strips lost moisture more slowly both in frying and in baking.