Gelation properties of extruded lemon cell walls and their water-soluble pectins

Functionalization of Enzymatically Treated Apple Pomace from Juice Production by Extrusion Processing

Food by-products can be used as natural and sustainable food ingredients. However, a modification is needed to improve the technofunctional properties according to the specific needs of designated applications. A lab-scale twin-screw extruder was used to process enzymatically treated apple pomace from commercial fruit juice production. To vary the range of the thermomechanical treatment, various screw speeds (200, 600, 1000 min⁻¹), and screw configurations were applied to the raw material. Detailed chemical and functional analyses were performed to develop a comprehensive understanding of the impact of the extrusion processing on apple pomace composition and technofunctional properties as well as structures of individual polymers. Extrusion at moderate thermomechanical conditions increased the water absorption, swelling, and viscosity of the material. An increase in thermomechanical stress resulted in a higher water solubility index, but negatively affected the water absorption index, viscosity, and swelling. Scanning electron microscopy showed an extrusion-processing-related disruption of the cell wall. Dietary fiber analysis revealed an increase of soluble dietary fiber from 12.6 to 17.2 g/100 g dry matter at maximum thermo-mechanical treatment. Dietary fiber polysaccharide analysis demonstrated compositional changes, mainly in the insoluble dietary fiber fraction. In short, pectin polysaccharides seem to be susceptible to thermo-mechanical stress, especially arabinans as neutral side chains of rhamnogalacturonan I.

The Influence of Extrusion Processing on the Gelation Properties of Apple Pomace Dispersions: Involved Cell Wall Components and Their Gelation Kinetics

By-products of fruits and vegetables like apple pomace can serve as techno-functional ingredients in foods. Due to their physicochemical properties, e.g., viscosity, water absorption, or oil-binding, food by-products can modify the texture and sensory perception of products like yogurts and baked goods. It is known that, by extrusion processing, the properties of by-products can be altered. For example, by thermo-mechanical treatment, the capacity of food by-products to increase viscosity is improved. However, the mechanism and involved components leading to the viscosity increase are unknown. Therefore, the complex viscosity of apple pomace dispersions and the involved fractions as pectin (a major part of the water-soluble fraction), water-soluble and water-insoluble fraction, were measured. In the investigated range, an increase in the pectin yield and water solubility was observed with increasing thermo-mechanical treatment by extrusion processing. However, pectin and water-soluble cell wall components had only a limited effect on the complex viscosity of apple pomace dispersions. The insoluble fraction (particles) were investigated regarding their swelling behavior and influence on the complex viscosity. An intensification of thermo-mechanical treatment resulted in increasing swelling behavior.

Modification of Apple Pomace by Extrusion Processing: Studies on the Composition, Polymer Structures, and Functional Properties

By-products of fruit and vegetable processing are an inexpensive and sustainable source of dietary fiber, potentially offering valuable functional properties such as water binding and thickening. Due to these favorable properties, they can be utilized to reformulate widely-consumed foods, e.g., bakery products or beverages. In this study, apple pomace was used as a model system to study whether extrusion technology affects food by-product functionality and thus has the potential to broaden the application of by-products in foods. The effect of the process parameters and the extent of thermo-mechanical treatment on the structural and functional properties of apple pomace were analyzed after extrusion trials using various screw speeds, water contents, and barrel temperatures. Compared to the raw material, apple pomace extruded at T_barrel = 100 °C, n = 700 min^-1 and m_H2O = 17% showed an increased water solubility up to 33%. The water absorption increased from 5 to 19 Pa·s and the paste viscosity from 5 to 339 Pa·s by extrusion processing. Analyses of dietary fiber contents and fiber polysaccharide structures revealed that thermo-mechanical stress (n = 700 min^-1, m_H2O = 22%) increased the content of soluble dietary fiber from 12.5 to 16.7 g/100 g dry matter, and that the harshest conditions even enabled the formation of low-molecular-weight dietary fiber. Arabinans (as neutral rhamnogalacturonan I side chains) appeared to be most sensitive to thermo-mechanical stress, whereas xylans (i.e., a group of minor polysaccharides) were an example of a more stable fiber polysaccharide. Also, the degree of methylation of the pectic polysaccharides was strongly reduced from 50% to 15% when thermo-mechanical stress was applied. Imaging and pore size analysis showed that extrusion processing could disrupt the rigid cell wall macromolecular structure.

Radiation Degradation of β-Glucan Extracted from Brewer’s Yeast for Enhancing Growth Promotion and Immunostimulant Activities on Broilers

Water-soluble low molecular weight β-glucan (WSLMG) was successfully prepared via γ-irradiation of insoluble β-glucan extracted from brewer’s yeast cell walls. The WSLMG content in an irradiated sample increased as the irradiation dose increased. The WSLMGs with a molecular weight (Mw) of 49, 25, and 11 kDa, obtained at correlative doses of 100, 200, and 300 kGy, respectively, were tested using growth promotion and immune stimulant effects in broilers. Supplementation with 500 ppm WSLMGs not only increased the survival rate (33.3%) and average body weight (40%) but also reduced the feed conversion rate (35.4%) in tested broilers. In addition, WSLMGs enhanced both nonspecific and specific immune components in the blood of supplemented broilers. The WSLMG with Mw ~25 kDa showed the highest effect on the growth performance and immunomodulatory capability in the immune systems of the tested broilers. In conclusion, this product demonstrates substantial promise as an immunostimulant and growth-promoting additive for poultry.

Health-related effects and improving extractability of cereal arabinoxylans

Arabinoxylans (AXs) are major dietary fibers. They are composed of backbone chains of β-(1-4)-linked xylose residues to which α-l-arabinose are linked in the second and/or third carbon positions. Recently, AXs have attracted a great deal of attention because of their biological activities such as their immunomodulatory potential. Extraction of AXs has some difficulties; therefore, various methods have been used to increase the extractability of AXs with varying degrees of success, such as alkaline, enzymatic, mechanical extraction. However, some of these treatments have been reported to be either expensive, such as enzymatic treatments, or produce hazardous wastes and are non-environmentally friendly, such as alkaline treatments. On the other hand, mechanical assisted extraction, especially extrusion cooking, is an innovative pre-treatment that has been used to increase the solubility of AXs. The aim of the current review article is to point out the health-related effects and to discuss the current research on the extraction methods of AXs.

Palmyra palm (Borassus aethiopum Mart.) fruits: novel raw materials for the pectin industry

BACKGROUND

Preventing post-harvest waste of Palmyra palm (Borassus aethiopum Mart.) fruits is possible by recovery of pectin as a value-added ingredient. Extraction conditions on yield and functionality of Palmyra palm pectin was determined at different temperatures and pH values with 30 min extraction time.

RESULTS

Palmyra palm fruits contain more than 650 g kg^-1 galacturonic acid and produce soft gels with sucrose in acidic media despite a high degree of acetylation (∼5%). Mechanical deformation of pectin gel was similar when extracted at pH 2.5 and 70 °C or under natural pH at room temperature or 70 °C. Pectins isolated at pH 7 exhibited comparable gel softness (G'/G″) with commercial pectin. Palm pectins also showed emulsifying activity greater than 50%, attributed to high protein content of 8 g 100 g^-1 . For pectins extracted at pH near 5.2-5.5, molar mass ranged from 3.00 to 3.38 × 10⁵ g mol^-1 ; intrinsic viscosity ranged from 218 to 297 mL g^-1 ; arabinose was the main neutral sugar; ζ-potential ranged from -23 to -25 mV.

CONCLUSION

Palm fruit offers an inexpensive raw material to extract pectin in environmentally friendly and economical way and yield a pectin with unique gelling, viscosifying and emulsifying properties. © 2016 Society of Chemical Industry.

Extrusion and Extruded Products: Changes in Quality Attributes as Affected by Extrusion Process Parameters: A Review

Extrusion of foods is an emerging technology for the food industries to process and market a large number of products of varying size, shape, texture, and taste. Extrusion cooking technology has led to production of wide variety of products like pasta, breakfast cereals, bread crumbs, biscuits, crackers, croutons, baby foods, snack foods, confectionery items, chewing gum, texturized vegetable protein (TVP), modified starch, pet foods, dried soups, dry beverage mixes etc. The functional properties of extruded foods plays an important role for their acceptability which include water absorption, water solubility, oil absorption indexes, expansion index, bulk density and viscosity of the dough. The aim of this review is to give the detailed outlines about the potential of extrusion technology in development of different types of products and the role of extrusion-operating conditions and their effect on product development resulting in quality changes i.e physical, chemical, and nutritional, experienced during the extrusion process.

Physicochemical and in vitro binding properties of barley β-glucan treated with hydrogen peroxide

This study investigated the changes in content, purity, physical properties, and in vitro binding properties of barley β-glucan by oxidation treatment. Barleys (Hordeum vulgare) were oxidized, using different concentrations of hydrogen peroxide (0.2-1.0% H2O2). The total and soluble β-glucan contents ranged from 8.41% and 4.81% in the control to 9.48% and 6.45% in the 0.6% H2O2 treatment. With increasing H2O2 concentration, the purity of β-glucan increased from 35% to 70%, whereas molecular weight (MW), viscosity, and water-binding capacities decreased to 2.0 × 10(4)Da, 3.9 cP, and 4.45 g water/g β-glucan, respectively. Oil binding capacities ranged from 8.29 g of oil/g in non-oxidized β-glucan to 9.42 g of oil/g in β-glucan oxidized with 0.6% H2O2. The MW, viscosity, and binding capacities of waxy barley β-glucan were higher than those of non-waxy barley β-glucan. Oxidation by hydrogen peroxide improved the physical properties and in vitro binding capacity of barley β-glucan.

Physicochemical Properties of β-Glucan from Acid Hydrolyzed Barley

This study was performed to investigate changes in the content and purity, as well as physical characteristics of β-glucan extracted from acid hydrolyzed whole grain barleys. Waxy and non-waxy barleys (Hordeum vulgare) were hydrolyzed with different concentrations of HCl (0.1~0.5 N) for 1 h. As the HCl concentration increased, the contents of total and soluble β-glucan from acid hydrolyzed barley decreased. However the ratio of soluble/total β-glucan content and purities of β-glucan significantly increased. The ratio of β-(1→4)/β-(1→3) linkages, molecular weight, and viscosity of soluble β-glucan of raw barleys were 2.28~2.52, 6.0~7.0×10(5) g/mol, and 12.8~32.8 centipoise (cP). Those of isolated soluble β-glucan were significantly decreased to 2.05~2.15, 6.6~7.8×10(3) g/mol, and 3.6~4.2 cP, respectively, with increasing acid concentration. The re-solubility of raw barley β-glucan was about 50%, but increased to 97% with increasing acid concentration. Acid hydrolysis was shown to be an effective method to produce β-glucan with high ratio of soluble β-glucan content, purity, water solubility, and low viscosity.

Natural bioactive compounds of Citrus limon for food and health

Citrus genus is the most important fruit tree crop in the world and lemon is the third most important Citrus species. Several studies highlighted lemon as an important health-promoting fruit rich in phenolic compounds as well as vitamins, minerals, dietary fiber, essential oils and carotenoids. Lemon fruit has a strong commercial value for the fresh products market and food industry. Moreover, lemon productive networks generate high amounts of wastes and by-products that constitute an important source of bioactive compounds with potential for animal feed, manufactured foods, and health care. This review focuses on the phytochemistry and the analytical aspects of lemon compounds as well as on the importance for food industry and the relevance of Citrus limon for nutrition and health, bringing an overview of what is published on the bioactive compounds of this fruit.

Antioxidant and Cancer Cell Proliferation Inhibition Effect of Citrus Pectin-Oligosaccharide Prepared by Irradiation

Pectin was dissolved in deionized distilled water (2%, vol/vol) and irradiated at 20 kGy using a Co-60 gamma ray irradiator. The resulting solution was dialyzed and lyophilized. The samples were separated into three groups to estimate their antioxidant and cancer cell proliferation effects: non-irradiated (0 kGy), irradiated (20 kGy), and dialyzed (20 kGy-F, mol wt <10,000) samples. Antioxidant properties of each treatment was tested by a beta-carotene-linoleic acid bleaching assay and electron donating ability and compared for antioxidant index, which indicated that the activity was higher in the order of 20 kGy-F > 20 kGy > 0 kGy. Spleen cell survival effect of the irradiated pectin (20 kGy) and dialyzed (20 kGy-F) samples was higher than the non-irradiated control (0 kGy). The pectins inhibited growth of the cancer cell in the order of 20 kGy- F > 20 kGy > 0 kGy. The Ames test revealed that none of the fractions was mutagenic, and there was no indication of a dose-dependent response for any of the samples. These results suggest that a functional pectin oligosaccharide can be produced by irradiation for the food industry without any chemical treatment.