Deep‐fat frying under moderate vacuum of potato cylinders

Abstract

Summary This study evaluates parameters relating to the mass transfer during the frying of potato cylinders at different temperatures (100, 120 and 140 °C) and moderate vacuum (around 25 kPa). In all cases, there is a linear relation between water loss and fat uptake. The parameters relating to the textural and structural modifications show less marked changes in vacuum fried products compared to those fried under atmospheric pressure. The maximum penetration force reaches 30%–40% of the initial hardness in vacuum frying and 10% for atmospheric pressure frying; starch gelatinization and pectin methylesterase enzyme activity reduce more quickly under atmospheric pressure, although after 240 s both values are negligible. The scanning electron microscopy images verify that the surface of potato cylinders fried under vacuum or atmospheric pressure are completely different as a result of the steam being released at different temperatures.

Reduction in hydroxymethylfurfural content in ‘churros’, a Spanish fried dough, by vacuum frying

“…This situation then stabilises and the values barely change over the remaining time. For a given frying time under vacuum, the oil content increases with the temperature, as has also been observed in vacuum frying of chips (Garayo & Moreira, ) and potato cylinders (Mir‐Bel et al ., ). For frying times shorter than 2 min, the ‘churros’ fried at atmospheric pressure have a similar oil content to those fried under vacuum with the same thermal gradient (100 °C).…”

“…Although the product is initially frozen, the hardness is always greater at the end of the process than at the beginning, possibly because the thawing takes place during the depressurisation period. The rapid increase in the maximum cutting force at the start of frying is because the crust forms very quickly and there is no initial softening at the surface, unlike the case of other products such as potatoes (Pedreschi et al, 2001;Mir-Bel et al, 2012a). This crust increases in thickness during the frying time until practically all the 'churro' becomes crust.…”

“…Despite the advantages apparently provided by this technique, there are few research studies about the frying at reduced pressure of products of considerable thickness such as ‘churros’ (Tan & Mittal, ; Mir‐Bel et al ., ,b). It has been shown that the crust formed at the product surface is about 1‐2 mm thick for products such as French fries when frying at atmospheric pressure, while it comprises the whole product in the case of chips (Moreira et al ., ).…”

“…The differences between chips and other thicker products could explain the apparent inconsistencies in the results of the studies on chips cited above, and those obtained by Tan & Mittal (2006) who concluded that donuts fried at vacuum conditions had similar moisture and improved colour but higher oil content than those fried in standard atmospheric conditions. To help complete the research about vacuum frying of thick products, the fat uptake and the moisture loss of potato cylinders fried at vacuum conditions were evaluated in a previous work (Mir-Bel et al, 2012a). In this case, the study was centred on texture and related parameters (PME activity, starch gelatinisation, SEM images).…”

Influence of vacuum deep fat frying process on quality of potato variety Primavera snacks: a functional food with antioxidant properties

“…Vacuum frying (VF) is a process that presents some advantages compared to conventional frying: the process carried out under lower pressure conditions than the local atmospheric pressure (lower partial pressure of O2), and lower frying temperatures; reducing final product and oil deterioration processes, in addition it diminishes the oil absorbed by the product and the formation of acrylamides and other toxic compounds, improving the nutritional, physical, sensorial properties and the contents of compounds with physiological activity present in the food [18]. VF has been used with positive results in a wide variety of fruits and vegetables such as apples, bananas, kiwifruits, mushrooms, potatoes, sweet potatoes, purple yam, among others [7].…”