In the vacuum frying process, oil is used
as heat exchanging medium to heating the raw material such as banana slices,
jackfruit… and promote the moisture vapored to gas, to attain the aim of
drying. Certainly, the oil also has the function of adjusting the vacuum fried
chips flavor. Due to oil touches vacuum fried chips directly, the oil quality
influences the final vacuum fried chips quality. Thus choose one higher quality
oil is also one important work for vacuum frying production.
The factors that determine the quality of
oil are stability and oxidability. Let’s analyse them
based on different oils’ characteristics together.
1. Stability
Oils with low stability are not suitable
for frying. The stability of fats is not only reflected in the oxidation rate
of fats, but also reflected in other changes, including the decrease of
unsaturated fats, the increase of free fatty acids, annular fatty acids and
polar substances, and the decrease of nutritional value and functionality of
fats. Among natural oils and fats, butter, cocoa butter and cream are
relatively stable, with a stability value of 2.3-2.4, followed by lard and palm
oil, with a stability value of 1.5-2.0. Among vegetable oils, peanut oil is
relatively stable, with a stability value of 1.2. Other oils and fats are 1.0
or below, such as soybean oil and sunflower oil.
2. Oxidability
Considering the oxidation rate of fat, we
should first consider the amount of fatty acid it contains, because the
oxidation rate of fatty acid determines the oxidation degree of fat. In
general, saturated fats are the most stable and least oxidized. The oils with
different amounts of saturated fatty acids rank from high to low: palm oil-animal
oil-olive oil and camellia oil- peanut oil-sunflower oil and corn oi-soybean
oil-rapeseed oil-safflower oil, flax oil and so on.
From the above analysis, we can draw a conclusion: butter, palm oil and animal could be used for vacuum frying. why do we finally choose palm oil? From economic perspective, the cost of butter is highest for big scale vacuum frying fruit and vegetable chips production; from health perspective, animal oil contains more cholesterol.
Thus palm oil is the
first choice for vacuum frying.
