Changes of pectic substances concentration in potatoes and French fries and the effect of these substances on the texture of the final product

Abstract

The texture of fried potato products depends on the building elements present in the cell walls, which play the structure-forming function, as well as on physical and biochemical changes of those elements which take place in the potato tissue, when it is exposed to blanching or frying. For the research the tubers of four potato varieties (Ekra, Orlik, Sumak, and Bryza) were used, which served as material for the production of French fries. In the samples of potato tubers before and after peeling, as well as in French fries blanched in the solutions of 0.4% CaCl2 and 0.4% MgCl2 salts the contents of pectic substances and their effect on the texture of the final product were determined. The process of peeling potato tubers contributed to the decrease of the content of the pectic substances. On the average 20% of the content of water-soluble pectins and about 5% of protopectins was decreased. Water blanching and frying contributed to a further decrease of the pectic substances in French fries in relation to their content in the raw material. However, potato strips blanching in the solutions of calcium and magnesium salts prevents further loss of those substances in the final product. The presence of calcium and magnesium ions in the solution of the blanching salts caused their partial binding by the pectin substances present in the potato tissue, which resulted in the improvement of the texture of French fries, especially obtained from early potato varieties.

The effect of frying on fat uptake and texture of fried potato products*

“…It was proved that the texture of French fries and potato crisps is conditioned not only by the content of dry matter and starch in potato tubers of different cultivars, but also by the content of proteins and non–starch polysaccharides and lignin. Pectic compounds, especially soluble pectins and protopectins, are known to be texture‐forming substances . These substances, as structural components of cell walls form not only the texture of the raw material, but also the texture of the ready product .…”

“…Pectic substances and starch present in the cells exert antagonistic effects on the texture. When starch swells, the cells become larger, and consequently, they become separated, while pectic compounds prevent this phenomenon, due to their cohesive effect .…”

Effect of Calcium Fertilization on Processing Properties and Storability of Frozen French Fries

“…French fries are a popular food world-wide because of their pleasant taste, which is created by the combination of a crispy crust, soft inside and typical fried potato flavor (Van Loon et al properties of potato contribute to the texture as well as the oil uptake of French fries (Kirkpatrick 1956;Johnston et al 1970;Sayre et al 1975;Aguilar et al 1997;Khalil 1999;Tajner-Czopek 2003;Tajner-Czopek and Figiel 2003;Golubowska 2005). For example, Johnston et al (1970) reported that the texture of French fries was positively correlated with starch content, dry matter content and specific gravity of raw potato tubers; and higher viscosity and swelling power of starches isolated from raw potatoes were associated with lower hardness of French fries.…”

Modeling the effect of blanching conditions on the texture of potato strips

“…It is through blanching that enzymes are inactivated (Tajner-Czopek, 2003;Tijskens et al, 1997), sugars leached out (Gekas, Ö ste, & Lamberg, 1993;Kaymak & Kincal, 1994), starch gelatinized, and cell separation achieved (Nonaka, 1980). The need to achieve all these objectives simultaneously constrains the choice of blanching temperature and time.…”