1. Introduction
In April 2002, the Swedish National Food Administration and the University of Stockholm published data, on the acrylamide content in many foods, such as bread, fried foods, and coffee. Acrylamide is formed during hightemperature processing by the Millard reaction which requires the presence of amino acids, asparagines and reducing sugars, low moisture content. The Swedish National Food Administration reported that fried food products such as chips contain the highest amount of acrylamide. At the laboratory scale, acrylamide causes tumors in animals. World Health Organization (WHO) and the Scientific Committee for Food (SCF) of the European Union (OSCF, 2002) revealed that the concentration of was high in potato chips, and breakfast cereals. This might represent a potential threat to public health.
The concentration of acrylamide in potato chips depends on the type of frying oil, and frying temperature. Acrylamide is created by the thermal reaction of natural potato components when moisture levels become low. Moreover, several factors, such as the initial concentration of amino acids, asparagines and reducing sugars, their ratio, heating temperature, processing time, pH, and moisture content of the product, affect the level of acrylamide in heatprocessed foods. The average daily food intake of acrylamide is in the range of 0.3 – 0.8 µg / kg body weight / day. Depending on current reports, the daily dietary intake of acrylamide is about 0.4 µg / kg body weight, with a 90th percentile 0f 0.95 µg / kg body weight. In some previous researches, it was indicated that the temperature is required to be higher than 120°C for the development of acrylamide. The effect of microwave frying on acrylamide content of potato strips has also been studied and the results showed that the acrylamide content of microwave fried potatoes was lower compared to those fried in conventional deep fryer because of the shorter frying time. Moreover, Microwave frying resulted in lower acrylamide formation in the coatings prepared by different types of flours as compared to conventional frying.
Microwaves offer many advantages in certain food processing operations primarily short processing time, space and energy savings, as it ensures preservation of nutritional value, process control, and selective heating. Microwave heating mechanism differs from conventional methods. Volumetric heating is the most important feature of microwave heating. Absorption of microwave energy results in internal heat generation within product. However, in traditional heating methods, the heat is transmitted from the surface to the inside of the food. The popularity of microwave heating increases in heat treatment applications because of increasing preference for high quality products that can be prepared in a short period of time along with the development of technology. However, the effect of microwave frying on acrylamide content of potato strips has also been studied recently and it was found that the acrylamide content of microwave fried potatoes was lower compared to those fried in conventional deep fryer because of the shorter frying time. There are few studies in literature about the effects of microwave frying on acrylamide formation. However, there is no study in literature about the effect of microwave frying at different conditions on acrylamide level in the potato chips using RBD palm olein and corn oil. Therefore, the aim of this study was to investigate the effect of different microwave frying conditions on the acrylamide formation in microwaved-fried potato chips using RBD palm olein and corn oil.
2. Materials and Methods
2.1. Sample Collection
Russet Potatoes cultivar Goldrush, RBD palm olein (Seri Murni) and corn oil (Daisy) were purchased from a local supermarket. Acrylamide (99%) was obtained from Sigma (Diesenhofen, Germany). HPLC gradient grade acetonitrile was obtained from J. T. Baker (Deventer, Holland). Ultrapure water was used for the chromatographic analysis (MilliQ system, Millipore, Bedford, MA, USA). A Standard stock solution of 1 mg / mL acrylamide was prepared in ultra-pure water and stored between 2 and 5ºC until use. Aliquots of the above stock solution were diluted with ultrapure water to get concentrations of 50 - 250 µg / mL and used for HPLC analysis. The established calibration curve had good linearity, with R2 > 0.99.
The fresh potatoes were processed with these process peeled, washed with clean water and cut into disc-shaped slices of 2 mm in thickness and 5.8 cm in diameter. The regularity of the thickness of the slices was checked using a caliper. The potato slices were rinsed with distilled water to eliminate starch material on the surface and then blotted with paper towels before each experiment. The samples were placed in aluminium foil to avoid any moisture loss before further processing.
"to be continued in the next part"