Chemical, physical and sensory attributes of chips prepared with sweet potato flour

The objectives of this research were to develop chips from flour of sweet potato flesh (FSPF) or skin (epidermis) (FSPS) and white potato and to measure chemical, physical and sensory attributes of the chips.

Sweet potato (Ipomoea batatas, Lam) (SP) roots of orange flesh, red skim and a moist-type unknown cultivar were cut into 1.2 cm slices, immersed in 0.25% citric acid solution, heated in an atmospheric pressure blancher, pureed and dried with a double drum-dryer. FSPF and FSPS were produced separately. Individual SPF at levels of 25, 50, 75 and 100% of the amount of white potato flour were mixed together to produce flakes. Ingredients used in dough formulation included water, butylated hydroxyanisol and salt (used in one-half of the chips). A smooth sheath of dough of 0.1 mm thick was cut into circular pieces of 3.8 mm diameter and fried in oil. Chips were salted or unsalted, flushed with nitrogen gas or stored in air for 0, 2, 6 and 9 weeks and analyzed for beta-carotene, peroxide value (PV), color and firmness at each period of storage. Proximate composition, gross energy and mineral contents of unsalted chips were analyzed on the same day chips were produced. Salted and unsalted chips for sensory analysis were evaluated for color, texture and overall acceptability after storage of 9 weeks.

Crude fat content of chips with FSPF increased from 25 to 50% while chips with FSPS contained the greatest crude fat content at 100%. Dietary fiber tended to increase in chips with increased levels of SPF. As levels of SPF increased, retinol equivalents (RE) and PV of chips with FSPF or FSPS increased also. Chips of both SPF flushed with nitrogen gas gave greater RE and lower PV than chips held under air atmosphere. Salting the chips reduced RE and PV. RE of chips with FSPF decreased by 11.93% from 0 to 9 weeks storage while chips with FSPS decreased 5.97%. After 9 weeks storage, chips with FSPF yielded PV of 18.08 meg/kg fat as opposed to PV of 4.23 meg/kg fat for chips analyzed on the day of production.

Chips became firmer as the level of SPF increased. Salt, gaseous atmosphere and storage periods had little or no effect on firmness of chips. Hunter L values (lightness) of chips decreased and Hunter 'a' values (redness) and Hunter 'b' values (yellowness) increased as level of SPF increased. Nitrogen gas atmosphere of the package under which the chips were stored caused a reduction of the chip color. With extended storage, chips became lighter, and less red and yellow.

All chips prepared with 25 and 50% SPF were preferred by panelists. Generally, salted chips flushed with nitrogen gas were preferred over unsalted chips held under air atmosphere.