The effects of conventional and convection baking treatments on the texture of osmotically processed, par-fried, frozen potato strips

This research was undertaken to study the effects of two baking methods, conventional and convection ovens, on osmotically processed, pan-fried, frozen potato strips (OPPFPS). The finished potatoes were evaluated objectively for texture using a TAXT2 Texture Analyser II and a TA 200 French fry attachment. The OPPFPS also were evaluated by a sensory panel and these results were compared to the objective measurements. The relationship of sensory scores to each other was determined.

Fresh cut potato strips were osmotically processed in a 60° Brix, 43 DE, high-maltose com syrup solution at 21°C for 2 hr. The osmotic processing produced a 29% loss in moisture and <1% gain in solids, when compared to fresh-cut potato strips. The osmotically processed strips were par-fried in vegetable oil at 190°C for 15 sec and then frozen until needed. OPPFPS were baked at 204°C in a conventional oven for 12 to 21 min or a convection oven for 4 to 9 min.

OPPFPS baked 21 min in a conventional oven contained 47% total solids compared to 38% solids in strips baked 12 min. The OPPFPS baked 9 min in a convection oven contained 44% solids compared to 37% solids in strips baked 4 min. The fat levels in the strips did not change during baking in either oven. OPPFPS contained less fat on a caloric basis (12%) than typically baked, par-fried potato strips (35%) as reported by the USDA (1982).

Average forces (g) required for twenty 1-mm probes to move through 14-mm sections of ten strip samples of OPPFPS were determined. The average forces required to move through a 3.5-mm section of the OPPFPS surrounding the initial maximum force (PK1) were 1566 and 1371 g for strips baked in a conventional oven for 12 and 21 min, respectively. PK1 values were 2140 and 1511 g for strips baked in the convection oven for 4 and 9 min, respectively. The minimum force (MIN) required to move through the samples was 1022, 636, 1522, and 702 g, for the 12, 21, 4 and 9 min baking treatments, Respectively.

Sensory evaluation consisted of panelists scoring their perceptions of an "ideal" baked French fry and then evaluating baked OPPFPS on a scale from "not at all"=1 to "very much so"=6 for six texture, three flavor and overall acceptability attributes. The 21-min and 9-min baked OPPFPS were less crisp (2.9), less firm (3.1) and more soggy (2.9) than panelists perceived an "ideal" baked French fry (4.9, 4.2 and 1.5, respectively). The baked OPPFPS were similar in sweetness (2.4) to an "ideal" French fry (2.4). The 9-min baked OPPFPS were perceived as more oily (3.2) but no more greasy (2.9) than an "ideal" French fry (2.4 and 2.3, respectively).

Significant (≤0.05) correlations were found between instrumental PK1 and MIN values and sensory values for "firm" (0.64 and 0.55), "crispy" (-0.54 and -0.49), and "off-flavor" (-0.51 and -0.52). The instrumental PK1 values also were correlated with sensory values for oily (0.42) and soggy (0.41). Panelists' comments indicated that OPPFPS baked for 18 and 21 min in the conventional oven had "burned" flavors. Therefore, these times were too long for baking this type of product at 204°C. OPPFPS baked 9 min in the convection oven were scored most acceptable by the sensory panel. However, only 44% of the panelists found these potato strips from slightly to very much acceptable.