Kinetics of Moisture Loss and Oil Absorption of Pork Rinds during Deep-Fat, Microwave-Assisted and Vacuum Frying

The fat content of fried pork rinds is high, and alternative frying helps reduce the oil content and maintain their texture and taste. Different frying methods such as microwave-assisted, traditional deep frying and vacuum frying on the breaking force, color, microstructure, water loss and oil absorption attributes of fried pork rinds were evaluated in this study. The fat content of microwave-assisted and vacuum-fried pork rinds was lower (24.2 g/100 g dry weight basis (db) and 17.1 g/100 g db, respectively) than that (35.6 g/100 g db) of traditional deep-fat frying. Non-uniform, holy and irregular surface microstructures were obtained by vacuum frying due to rapid mass transfer at low pressure. The first-order kinetic models of water loss and oil absorption of traditional and microwave-assisted frying of pork rinds were established. Microwave frying caused a faster moisture loss rate, shorter frying time and lower pork rind oil content, makes it an attractive substitute for traditional deep-fat frying.

Prediction of the thermo-physical properties of deep-fat frying plantain chips (ipekere) using artificial neural network

This study uses artificial neural network (ANN) to predict the thermo-physical properties of deep-fat frying plantain chips (ipekere). The frying was conducted with temperature and time ranged of 150 to 190 °C and 2 to 4 minutes using factorial design. The result revealed that specific heat was most influenced by temperature and time with the value 2.002 kJ/kg°C at 150 °C and 2.5 minutes. The density ranged from 0.997 – 1.005 kg/m3 while thermal diffusivity and conductivity were least affected with 0.192 x 10−6 m2/s and 0.332 W/m°C respectively at 190 °C and 4 minutes. The ANN architecture was developed using Levenberg–Marquardt (TRAINLM) and Feed-forward back propagation algorithm. The experimentation based on the ANN model produced a desirable prediction of the thermo-physical properties through the application of diverse amount of neutrons in the hidden layer. The predictive experimentation of the computational model with R2 ≥ 0.7901 and MSE ≤ 0.1125 does not only show the validity in anticipating the thermo-physical properties, it also indicates the capability of the model to identify a relevant association between frying time, frying temperatures and thermo-physical properties. Hence, to avoid a time consuming and expensive experimental tests, the developed model in this study is efficient in prediction of the thermo-physical properties of deep-fat frying plantain chips.

Influence of Frying Methods on Quality Characteristics and Volatile Flavor Compounds of Giant Salamander (Andrias davidianus) Meatballs

Effects of deep fat frying and hot air frying on texture, color difference, sensory score, yield, fat content, and volatile flavor compounds of giant salamander meatballs before and after frying were investigated. The results showed that, compared with the deep fat frying group, hot air-fried giant salamander meatballs had higher hardness, elasticity, and L ∗ ( p < 0.05 ), but lower a ∗ , b ∗ value, fat content, and yield ( p < 0.05 ). There was little distinction in sensory score, cohesiveness, and chewiness between the two frying methods ( p > 0.05 ). Gas chromatography ion migration chromatography (GC-IMS) was used for flavor compound analysis, and 50 flavor compounds were analyzed, containing 22 aldehydes, 11 ketones, 6 olefins, 4 acids, 3 esters, 3 alcohols, and 1 phenol. Compared with the samples before frying, the relative contents of aldehydes and ketones of fried giant salamander meatballs increased significantly, while the relative contents of esters and alkenes decreased significantly. Principal component analysis showed that the GC-IMS spectra of volatile flavor compounds before and after deep fat frying and hot air frying varied greatly, and the cumulative contribution rate of the two principal components reached 86.1%, indicating that the GC-IMS technology might be used to distinguish giant salamander meatballs before and after frying, or with different frying methods. These results may offer a note for development and quality control of the precooked giant salamander meatballs in the future.

EFFECT OF REPEATED DEEP-FAT FRYING OF FRENCH FRIES IN SUNFLOWER AND PALM OILS ON THE ACRYLAMIDE CONTENT

The study aimed to investigate the influence of repeated frying processes of potatoes in a fryer on the acrylamide content of French fries. For deep-frying, potatoes of the Asinaria variety, sunflower and palm oils were used. For each oil type, five frying cycles at 170°C, for 6 min were performed and the acrylamide content of the final product was analyzed using the solid phase extraction (SPE) technique and the GC-MS/MS method. The acrylamide content increased in the case of sunflower oil in the first three frying cycles, while for palm oil it increased in the fourth frying cycles, then a decrease was recorded. The mean acrylamide content of French fries samples fried in sunflower oil (1477.07 μg/kg) was higher than the one of French fries fried in palm oil (1258.95 μg/kg). For all samples analyzed, the acrylamide content exceeded the benchmark level of 500 μg/kg settled by the EU 2017/2158. The acrylamide content of French fries was correlated with the color parameter L*.