Preparation of dietary fiber concentrate from Tunisian lemon (Citrus limon L.) by-products: Physico-chemical, functional and antioxidant properties

Dietary fibers constitute an important element of a healthy diet. This study is a contribution to valorize Tunisian lemon (Citrus limon L.) by-products (LB) by preparation of a lemon fiber concentrate (LFC). The suitability of this by-product as a source of dietary fiber for food enrichment was investigated. Lemon fiber concentrate was prepared by LB washing in water at 90 °C for 5 min and then characterized by studying its physico-chemical, functional and antioxidant properties, in comparison with the original LB. The extraction method led to a total dietary fiber yield of 54.42 g/100g. LFC had higher content in total fibers than LB (71.20 versus 63.87 g/100g dry matter (DM), respectively), with predominance of the insoluble fraction (53.58 g/100g DM). LFC had also better functional properties, with higher water holding capacity (13.92 versus 8.51 g/g, respectively), swelling capacity (14 versus 8.75 ml/g, respectively) and oil retention property (6.6 versus 4.43 g/g, respectively). LFC had high content in bioactive compounds, particularly for phenolics (561.09 mg GAE/100 g DM) and flavonoids (408.42 mg QE/ 100 g DM), which gave it good antioxidant properties (antiradical activity: 45.57 % and reducing power: 0.18). The results of this study suggested that LFC may have potential applications for food enrichment.

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

Shale oil is a vital alternative energy source for oil and gas and has recently received an extensive attention. Characterization of the shale oil content provides an important guiding significance for resource potential evaluation, sweet spot prediction, and development of shale oil. In this paper, the mechanism, evaluation and influencing factors of oil retention in shales are reviewed. Oil is retained in shales through adsorption and swelling of kerogen, adsorption onto minerals and storage in shale pores. Quite a few methods are developed for oil content evaluation, such as three-dimensional fluorescence quantitation, two-dimensional nuclear magnetic resonance (2D NMR), solvent extraction, pyrolysis, multiple extraction-multiple pyrolysis-multiple chromatography, logging calculation, statistical regression, pyrolysis simulation experiment, and mass balance calculation. However, the limitations of these methods represent a challenge in practical applications. On this basis, the influencing factors of the oil retention are summarized from the microscale to the macroscale. The oil retention capacity is comprehensively controlled by organic matter abundance, type and maturity, mineral composition and diagenesis, oil storage space, shale thickness, and preservation conditions. Finally, oil mobility evaluation methods are introduced, mainly including the multitemperature pyrolysis, 2D NMR, and adsorption-swelling experiment, and the influencing factors of movable shale oil are briefly discussed. The aim of this paper is to deepen the understanding of shale oil evaluation and provide a basis for further research.

Influence of Thermochemical Treatment on the Surface Properties of Finish Turned Wire Arc Sprayed 17Cr Steel Coatings

Structural features of thermal spray coatings, e.g., porosity, can be beneficial as oil retention volumes in tribological systems in order to improve emergency running properties. While thermal spray coatings can already have a considerable degree of porosity depending on the coating conditions, the finish machining, e.g., by turning, has a significant influence on the final surface properties. Effects like near-surface deformation and subsequent closing of pores during the machining process should be prevented. In the present study, the influence of thermochemical surface hardening on the surface topography of wire arc sprayed 17Cr steel layers after finish turning was investigated. Successful surface hardening by gas nitriding was shown by light microscopic and phase analyses. The surface properties after the various treatment steps were characterized by the surface roughness parameters Ra and Rz, the valley void volume Vvv, and the Abbott curves. A rise of the valley void volume can be beneficial in tribological applications in which a suitable oil retention volume is required. Accordingly, a thermochemical treatment combined with an appropriate subsequent finishing process is suitable to significantly influence the surface properties of thermal spray steel coatings.

Chemical Composition and Functional Properties of Dietary Fibre Concentrates from Winemaking By-Products: Skins, Stems and Lees

The objective of this study was to evaluate, from a technological and nutritional point of view, the chemical composition and functional properties of the industrial winemaking by-products, namely skins, stems and lees. The chemical and physical characteristics, as well as the functional properties (fat and water retention and swelling capacity, antioxidant capacity, and their prebiotic effect), of the dietary fibre of these by-products were studied. The results showed that the skins, stems, and lees are rich in fibre, with the stem fibre containing the highest amounts of non-extractable polyphenols attached to polysaccharides with high antioxidant activity and prebiotic effect. Lee fibre had the highest water retention capacity and oil retention capacity. The results reveal that winemaking by-products could be used as a source of dietary fibre with functional characteristics for food applications.

TRIBOLOGY AND TOPOGRAPHY OF HARD MACHINED SURFACES

In machining automotive industrial parts by hard machining procedures, the topographic characteristics of high accuracy surfaces have high importance. In this paper 2D and 3D surface roughness features of gear bores machined by hard turning and grinding are demonstrated. The 3D roughness parameters, which are considered as more exact than the 2D parameters, were compared to the 2D ones, which are used more widely in industrial practice. The analyzed machining procedure versions were ranked based on the topographic parameters determining the tribological (wear and oil-retention capability) characteristics of the different surfaces.