Influence of Degree of Gelatinization on Expansion of Extruded, Starch-Based Pellets during Microwave Vacuum Processing

Sugar boiling pre-treatment improves radio frequency explosion puffing quality on modifying the physicochemical and functional properties of purple sweet potato flour

The effects of sugar boiling pretreatment (SBP) with different maltitol concentrations (20 %, 30 %, and 40 %) and boiling time (0 - 6 min) on the physicochemical and functional properties of purple sweet potato flour and the radiofrequency explosion puffing (RFEP) quality were investigated. The results showed that the volume ratio, crispness, anthocyanin retention rate and overall acceptability of the samples were maximized after boiling for 6 min at 40 % maltitol concentration achieving increases of 78.63 %, 437.50 %, 392.25 % and 552.94 %, respectively compared to the control (p < 0.05). Fourier transform-infrared spectroscopy and X-ray diffraction analyses revealed that the flour underwent hydrogen bond breaking and formed hydrogen bonds with maltitol at high temperatures, forming maltitol starch-protein / lipid complexes, resulting in decreased crystallinity, short-range ordering, random coil, -helix and enthalpy, while the non-crystalline region area and -sheet increased. Additionally, the viscosity and storage modulus of the flour increased following pregelatinization. Conversely, as maltitol concentration increased, both viscosity and storage modulus decreased, facilitating the expansion of puffing volume due to the instantaneous total drainage of water upon pressure release. Furthermore, SBP effectively preserved the color and anthocyanin content of the chips. These findings may provide valuable insights for regulating oil-free puffing quality of starchy foods.

Evaluating microwave energy impact on 3G snacks: A study on dielectric properties and expansion

Third-generation (3G) snacks, a food type of widespread interest in the industry, have a longer shelf life than second-generation (2G) snacks. The primary regeneration process for these snacks involves frying and microwaving. However, only a few studies have detailed the effects of microwave irradiation on these products. This study aims to analyse the influence of the type of material, compression, and microwave power on the expansion capabilities of the pellets. Four raw materials (rice flour, rice semolina, corn semolina, and wheat starch) were combined with water to achieve uniform moisture content and extruded into pellets with different compression ratios (1:1, 2:1, and 3:1). The elaborated samples were processed at different microwave powers (heating rates of 2 and 10 °C/s) using an instrument capable of accurately delivering microwave energy to food samples while monitoring key process parameters, including dielectric properties. Samples with high starch content, low protein content, and low fibre content, in conjunction with higher compression ratios exhibited a more pronounced expansion.

Effect of Extrusion Temperature and Feed Moisture Content on the Microstructural Properties of Rice-Flour Pellets and Their Impact on the Expanded Product

Extrusion can lead to an expanded product or to a slightly expanded pellet, known as a third-generation (3G) snack. In this case, expansion occurs subsequently, in an independent thermal device (e.g., oven), out of the extruded pellet. During both processes, several structural changes occur which are linked to processing conditions, including cooking temperature, screw speed, formulation, and initial moisture content. However, a clear relationship between processing variables and the structure of pellets and expanded products has not yet been identified. Accordingly, this work aimed to study the effect of extrusion temperature (110, 135, and 150 °C) and moisture content (27, 29, and 31%) in rice-flour pellets and their microwave expansion, through a microstructural approach using micro-CT. The results showed that the lowest moisture content (27%) and the highest extrusion temperature (150 °C) led to the highest pellet volume and the highest wall thickness, which in turn led to the highest expansion after microwave heating (50 s, 800 W). Interestingly, no significant differences were observed when analyzing the ratio between the volume of the expanded products and the volume of the pellet (~2.4) when using the different processing conditions.

Optimization of the preparation process of mung bean puffed infant rice cereal and evaluation of the structure and digestion characteristics of starch

The present study was carried out to produce a high quality puffed infant rice cereal from rice and mung bean through extrusion technology. Experiments were designed using 3 independent variables (i. e. 14–18% feed moisture, 400–550 r/min screw speed and 125–175 °C barrel temperature) and 3 response variables (i. e. bulk density, water solubility index and degree of gelatinisation) at five different levels of central composite rotatable design (CCRD). The results of optimization demonstrated that 14% feed moisture, 400 r/min screw speed and 175 °C barrel temperature could generate rice-mungbean extrudates with desirable functional properties. The selected extrudate samples were further examined using scanning electron microscope (SEM), rapid viscosity analyzer (RVA), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) analysis, in vitro digestibility and fundamental nutrient analysis. Notably, the initial oval-shaped particle structure of starch in the raw materials disappeared, the surface debris and roughness increased, and the density decreased. The time required for the gelatinization of puffed infant rice cereal was the shortest, which was in agreement with the positioning of ready-to-eat weaning food for infants. Moreover, the puffed infant rice cereal displayed higher peak viscosity and breakdown value, smaller retrogradation value and greater top taste value compared to the commercial infant rice cereal. Besides maintaining the initial characteristic peak of starch, the puffed infant rice cereal demonstrated characteristic absorption peaks of COO- in the vicinity of 1546 cm−1 and 1437 cm−1, indicating the formation of carboxylate during extrusion. In addition, the puffed infant rice cereal exhibited firm diffraction peaks at the diffraction angles of 7.4°, 12.5° and 20.5°, indicating that a certain amount of starch changed from type A to type V. Furthermore, the digestive rate of puffed infant rice cereal was higher than that of commercial infant cereal (90.21 versus 86.96%, respectively; p < 0.05). Altogether, our findings reveal that the developed puffed infant rice cereal meets the standards set by the Codex Alimentarius Commission (CAC; 74-1981).

Effect of different flours on quality of legume cakes to be baked in microwave-infrared combination oven and conventional oven

The objective of this study was to compare the quality of legume cakes baked in microwave-infrared combination (MW-IR) oven with conventional oven. Legume cake formulations were developed by replacing 10 % wheat flour by lentil, chickpea and pea flour. As a control, wheat flour containing cakes were used. Weight loss, specific volume, texture, color, gelatinization degree, macro and micro-structure of cakes were investigated. MW-IR baked cakes had higher specific volume, weight loss and crust color change and lower hardness values than conventionally baked cakes. Larger pores were observed in MW-IR baked cakes according to scanning electron microscope (SEM) images. Pea flour giving the hardest structure, lowest specific volume and gelatinization degree was determined to be the least acceptable legume flour. On the other hand, lentil and chickpea flour containing cakes had the softest structure and highest specific volume showing that lentil and chickpea flour can be used to produce functional cakes.

Effects of salt on the expansion of starchy snacks: a multiscale analysis

We investigate the effect of salt on the expansion of starchy snacks during frying by means of a multiscale simulation model.