Physicochemical and Bioactive Properties of Soluble Dietary Fibers from Blasting Extrusion Processing (BEP)-Extruded Carrot Residues

A Review of the Changes Produced by Extrusion Cooking on the Bioactive Compounds from Vegetal Sources

The demand for healthy ready-to-eat foods like snacks is increasing. Physical modification of vegetal food matrices through extrusion generates significant changes in the chemical composition of the final product. There is a great variety of food matrices that can be used in extrusion, most of them being based on cereals, legumes, fruits, vegetables, or seeds. The aim of this review was to summarize the main effects of the extrusion process on the bioactive compounds content, namely phenolics, terpenes, vitamins, minerals, and fibers of vegetal mixes, as well as on their biological activity. The literature reported contradictory results regarding the changes in bioactive compounds after extrusion, mainly due to the differences in the processing conditions, chemical composition, physicochemical properties, and nutritional value of the extruded material and quantification methods. The thermolabile phenolics and vitamins were negatively affected by extrusion, while the fiber content was proved to be enhanced. Further research is needed regarding the interactions between bioactive components during extrusion, as well as a more detailed analysis of the impact of extrusion on the terpenes since there are few papers dealing with this aspect.

Physicochemical, structure properties and in vitro hypoglycemic activity of soluble dietary fiber from adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) bran treated by steam explosion

To enhance the content of adlay bran soluble dietary fiber (SDF) and improve its functionality, we investigated the influences of steam explosion (SE) on the physicochemical, structural properties, and in vitro hypoglycemic activities of adlay bran SDF. The cellulose, hemicellulose, and lignin contents of adlay bran decreased significantly after SE treatment. When the SE strength was 0.8 MPa for 3 min, the SDF content was 9.37%, which was a significant increase of 27.48% compared to the control. Under these conditions, SDF showed the highest oil-holding capacity (OHC) (2.18 g/g), cholesterol adsorption capacity (CAC) (27.29 mg/g), glucose adsorption capacity (GAC) (15.54 mg/g), glucose dialysis retardation index (GDRI) (36.57%), and α-Amylase activity inhibition ratio (α-AAIR) (74.14%). Compared with SDF from untreated adlay bran, SDF from SE-treated adlay bran showed lower weight molecular. In addition, differential scanning calorimetry (DSC) measurement showed that the peak temperature of SDF from adlay bran treated by SE increased by 4.19°C compared to the untreated SDF sample. The structure of SDF from adlay bran treated by SE showed that the SDF surface was rough and poriferous and the specific surface areas increased. In conclusion, SE pretreatment increases the content of SDF in adlay bran and improves its physicochemical, structural properties, and biological activities, which will be beneficial for the further exploitation of adlay bran.

Properties of plant-derived soluble dietary fibers for fiber-enriched foods: A comparative evaluation

Plant-derived soluble dietary fibers (SDF) have many important physiological functions and the applications of SDF vary based on their properties, which are worth further investigating for fiber-enriched food production. In this study, SDF derived from konjac, apple, chicory, flaxseed, orange, psyllium seed, soybean and oat were purified, and their structural, physicochemical and functional properties were systematically evaluated. Monosaccharide composition analysis showed that these SDF belonged to heteropolysaccharides, of which konjac, psyllium seed, apple, soybean and oat SDF were glucomannan, arabinoxylan, pectin, arabinogalactan and glucan, respectively. The molecular weight of konjac glucomannan (KGM, 5.22 × 10⁶ Da) was the highest, and inulin, soybean arabinogalactan (SA) and oat glucan (OG) had higher water solubility. Moreover, KGM, apple pectin (AP), flaxseed SDF (FS) and psyllium seed arabinoxylan (PA) exhibited better water-holding capacity, swelling capacity, emulsifying activity and stability. Rheological studies and texture profile analysis suggested that KGM had the best viscosity and gelation ability. In addition, AP and orange SDF (OS) showed better α-amylase inhibitory activity, while OS and KGM had higher pancreatic lipase inhibitory activity. Also, KGM and FS displayed fine cholesterol absorption capacity. To summary, these functional properties illustrated the feasibility of SDF to regulate blood sugar and blood lipid levels.

Effects of High-Temperature, High-Pressure, and Ultrasonic Treatment on the Physicochemical Properties and Structure of Soluble Dietary Fibers of Millet Bran

Objectives

The effects of high-temperature, high-pressure, and ultrasonic treatment on the physicochemical properties and structure of soluble dietary fibers in millet bran were studied to provide a comprehensive reference for the utilization of millet bran.

Methods

Different physical methods were used to treat millet bran dietary fibers, and their microstructures and Fourier-transform infrared spectra before and after modification were compared. The physicochemical properties (water-holding capacity, swelling capacity, oil-holding capacity, fat-binding capacity, cation exchange capacity), total antioxidant capacity, and thermal characteristics were also analyzed.

Results

There were no significant changes in the chemical groups of millet bran's soluble dietary fibers after modification, but cracks appeared on the surface of the fibers and the structure became loose and porous. Fiber agglomeration was observed, as well as improved thermal stability. After modification, the water-holding capacity, swelling capacity, oil-holding capacity, fat-binding capacity, and cation exchange capacity of millet bran were improved. When compared to the original soluble dietary fibers, ultrasound-treated fibers showed the most substantial improvement in all four capabilities, with increases of 140, 50, 78.1, 65.7, and 37.8%, respectively, compared with the original soluble dietary fibers (P < 0.05). The total antioxidant capacity of the ultrasound-treated fibers was found to be higher than those of the fibers that underwent the other three treatments (P < 0.05).

Conclusions

The physicochemical qualities and structural characteristics of the soluble dietary fibers in millet bran are affected by all three physical modification methods; however, the physicochemical properties of the ultrasound-treated fibers are most significantly improved.

Impact of Rapeseed Press Cake on the Rheological Properties and Expansion Dynamics of Extruded Maize Starch

Rapeseed press cake (RPC), an oil pressing side product rich in protein and fiber, can be combined with starch and valorized into directly expanded products using extrusion technology. The mechanism of starch expansion has been studied in detail, but the impact of RPC on expansion behavior is poorly understood. However, it can be linked to rheological and physicochemical properties and is a key product quality parameter. Blends with different amounts of RPC (0, 10, 40 g/100 g) were extruded at different barrel temperatures (100, 120, 140 °C) and moisture contents (24 or 29 g/100 g). The initial, intermediate and final sectional, longitudinal and volumetric expansion indices (SEI, LEI, VEI) were monitored directly, 10 s and 24 h after die exit to measure extrudate growth and shrinkage. The viscous and elastic properties of the extruded blends were investigated in a closed cavity rheometer. Starch and blends with 10 g/100 g RPC achieved a high initial SEI followed by significant short-term shrinkage. Blends containing 40 g/100 g RPC did not show any initial expansion. With increasing RPC content, the intermediate SEI decreased, but all samples reached a similar final SEI due to time-dependent swelling of the RPC blends. With increasing RPC content, the elasticity of the starch-based extruded samples significantly increased. Our study shows that comprehensive control and understanding of expansion mechanisms can be achieved only by investigating all stages of extrudate growth and shrinkage. We also found that the closed cavity rheometer is a powerful tool to correlate the rheological properties and expansion mechanisms of biopolymers.

Increasing soluble dietary fiber content and antioxidant activity of wheat bran through twin-screw extrusion pretreatment

As a by-product during flour production, wheat bran is mainly used as raw material for fodder or fermentation. In the present work, wheat bran was extruded with different moisture conditions and the consequently chemical component, absorption capacity, and antioxidant activity of treated wheat bran were analyzed. Results showed that extrusion decreased the particle size and crystallinity of wheat bran, but increased the soluble dietary fiber content of which from 3.08% to 11.78%. Meanwhile, water holding capacity, oil holding capacity for peanut oil and lard, and swelling capacity of WB-W-G-Na reached 5.67 g/g, 3.34 g/g, 3.58 g/g and 4.3 mL/g, respectively. Moreover, DPPH radical scavenging activity of WB-W-G-Na increased from 6.8% to 18.4% and hydroxyl radical scavenging activity increased from 5.3% to 15.9%. Overall, this work provides an excellent pretreatment method for increasing the functional activities of wheat bran in the food industry.

Sequential application of postharvest wounding stress and extrusion as an innovative tool to increase the concentration of free and bound phenolics in carrots

Postharvest wounding stress in carrots induces the accumulation of phenolics, whereas extrusion generates modifications in the nutritional profiles of food matrixes. In the present study, the sequential application of wounding stress and extrusion on total free and bound phenolics as well as on carotenoid profiles of carrots was evaluated. Wounding was applied by shredding carrots and storing the tissue (48 h, 15 °C). The stressed-tissue was dehydrated and extruded at 63 °C or 109 °C and at continuous or expansion screw configurations. Extrudates were milled and sieved before phytochemical analysis. Wounding increased total free (288.1%) and bound (407.6%) phenolic content, whereas the carotenoid content was unaltered. The free and bound phenolics that showed the highest increase due to wounding were the chlorogenic (579.8%) and p-coumaric (390.9%) acids. Extrusion, at 109 °C under expansion screw configuration, further increased the wound-induced accumulation of total free (296.6%) and bound (22.1%) phenolics and induced trans-cis isomerization of β-carotene.

Optimization of the extrusion process for preparation of soluble dietary fiber-enriched calamondin pomace and its influence on the properties of bread

Calamondin pomace is a by-product obtained after calamondin juice extraction. The effects of extrusion variables on the soluble dietary fiber (SDF) of calamondin pomace were investigated by response surface methodology. Bread samples with different contents of extruded calamondin pomace (ECP) additive were produced and their textural and sensory properties evaluated. The optimal conditions for the extrusion of calamondin pomace were found to be a barrel temperature of 129 °C, feed moisture of 16%, and a screw speed of 298 rpm. The results revealed that extrusion increased the SDF of the calamondin pomace because the redistribution of insoluble dietary fiber formed SDF. A monosaccharide profile indicated that total dietary fiber in calamondin pomace processed by extrusion contained a high content of uronic acid and arabinose and a low amount of glucose, suggesting the presence of pectic polysaccharide and trace amounts of cellulose and hemicellulose. Increasing the ECP content decreased the specific volume and altered the textural properties, such as the hardness, gumminess and chewiness of the bread, and the bread became darker and redder in appearance. Sensory evaluation indicated that bread with 5% ECP content had good overall acceptability. Thus, extrusion of calamondin pomace can effectively increase the SDF content and resulting ECP can be used to produce SDF-enriched breads with sensory acceptability.

Enrichment of soybean dietary fiber and protein fortified rice grain by dry flour extrusion cooking: the physicochemical, pasting, taste, palatability, cooking and starch digestibility properties

With the prevalence of chronic conditions in patients due to a dietary imbalance, the demand for inexpensive, nutritious and high dietary fiber extruded rice is increasing rapidly. However, the factors of quality and bioavailability are still the major constraints to its development. In this study, soybean dietary fiber (DF) and protein fortified rice grain were prepared via dry flour extrusion processing. The results showed that the extruded rice had a similar density to that of natural rice and a significantly lower whiteness degree and transparency. Notably, the cooking texture and palatability of extruded rice were affected by the added amount of DF, resulting in rice with a taste value close to 70 in DF 6-9% (w/w) samples. The pasting properties, microstructure, and molecular interactions according to RVA, SEM and FTIR analyses, respectively, were also significantly affected by the DF content. The soluble dietary fiber was significantly increased from 0.0021 g g-1 to 0.216 g g-1 in extruded rice. Importantly, the starch digestibility in vitro showed significantly lower readily digestible starch (RDS) and higher resistant starch (RS) in DF 6-15% (w/w) extruded rice than in natural rice and DF-0 rice, respectively. The glycemic index (GI) was reduced in DF > 6%. In this study, we provide a new high dietary fiber extruded rice product with good texture and palatability, and we reveal the effect of DF on the extruded rice properties.

Modification of carrot (Daucus carota Linn. var. Sativa Hoffm.) pomace insoluble dietary fiber with complex enzyme method, ultrafine comminution, and high hydrostatic pressure

Insoluble dietary fiber (DF) extracted from carrot pomace was modified by complex enzyme method, ultrafine comminution and high hydrostatic pressure and their structural, physicochemical, and functional properties were evaluated. Results showed that complex enzyme method increased the content of soluble DF to 15.07%, and the cholesterol adsorption capacity peaked; ultrafine comminution greatly improved the total antioxidant activities, DPPH radical scavenging capacity and antioxidant abilities in linoleic acid system of DF; high hydrostatic pressure led to a significant increase in capacities of water retention (7.14 g/g, 600 MPa), water swelling (10.02 mL/g, 500 MPa), oil retention (2.35 g/g, 500 MPa), cation exchange (2.29 mmol/g, 600 MPa), and glucose adsorption (2.634 mmol/g, 400 MPa). Furthermore, SEM showed that surface structures of all modified DF were loose. Overall, three kinds of modification methods have shown their respective advantages. Modified DF from carrot pomace can be applied as a functional ingredient in diverse food products.

Physicochemical properties and intestinal protective effect of ultra-micro ground insoluble dietary fibre from carrot pomace

Carrot pomace is an abundant, but underutilized, byproduct from the juice industry.