Optimization of extruder cooking conditions for the manufacture of fish feeds using response surface methodology

Abstract A composite blend consisting of sunflower cake, maize germ, wheat bran, fresh water shrimps and cassava flour was extruded using a single‐screw extruder to produce expanded fish feed pellets. The effects of temperature (80–120 °C), die diameter (2–4 mm), and feed pre‐conditioning time (50–150 s; steam 400 kPa) on properties of the pellets (expansion ratio, bulk density, floatability, durability, water absorption, water solubility, water stability, and in‐vitro protein digestibility) were investigated using response surface methodology. Regression equations describing the effect of each variable on the product responses were obtained. The pellets extruded using a factor combination of 120 °C extruder barrel temperature, 2 mm die diameter, and 100 s of feed pre‐conditioning time gave most desirable pellet floatability (100%), durability index (99%), expansion ratio (2.64), water absorption index (4.12), water solubility index (9.31), water stability (87%), bulk density (479 g/L), and in vitro protein digestibility (69.97%) with a composite desirability of 0.88. Practical applications Extrusion is a modern feed processing method whose use is fast gaining popularity among small feed processors in developing countries. However, extrusion is a process that involves many parameters that need to be optimized for desirable end properties. These findings guide fish feed manufacturers on the optimum conditions for single screw extruders for production of feeds with desirable properties especially for the fish types that are top feeders. In addition, the results offer important insights on how temperature, die diameter, and feed pre‐conditioning, may be manipulated to influence properties of extruded aquafeed when using simple low‐cost small‐scale extruders

Production, properties, and applications of solid self-emulsifying delivery systems (S-SEDS) in the food and pharmaceutical industries

The food and pharmaceutical industries aim to develop innovative delivery systems to meet the increasing consumer demand for healthier and safer food products and to improve the efficacy of drug formulations, respectively. Many bioactive agents with beneficial physiological and pharmacological activities are difficult to deliver because of their poor water solubility, chemical instability, or low oral bioavailability. Nano- and micro-encapsulation technologies are therefore being developed to overcome these limitations. This review article provides an overview of several lipid-based carriers suitable for the encapsulation of nutraceutical and pharmaceutical molecules, including their structures, constituents, production methods, and applications. It then focuses on the preparation, characterization, and application of solid self-micro-emulsifying delivery system (S-SMEDS). Finally, potential challenges of using S-SMEDS and S-SNEDS as delivery systems in the food and pharmaceutical industries are addressed

Electrophysiological analysis of the negative chronotropic effect of endothelin-1 in rabbit sinoatrial node cells

Electrophysiological effects of endothelin-1 (ET-1) were studied in rabbit sinoatrial node (SAN) using conventional microelectrode and whole-cell voltage and current recordings.In rabbit SAN, RT-PCR detected ETA endothelin receptor mRNA. ET−1 (100 nm) increased the cycle length of action potentials (APs) from 305 ± 15 to 388 ± 25 ms; this effect was antagonised by the ETA receptor-selective antagonist BQ−123 (1 μm). ET-1 increased AP duration (APD50) by 22 %, depolarised the maximum diastolic potential (MDP) from −59 ± 1 to −53 ± 2 mV, shifted the take-off potential by +5 mV and decreased the pacemaker potential (PMP) slope by 15 %. Under exactly the same experimental conditions, ET-1 caused a positive chronotropic effect in guinea-pig SAN with a decrease of 13 % in APD50, a shift of −4 mV in the take-off potential and an increase of 8 % in the PMP slope.Rabbit SAN exhibited two major cell types, distinguished both by their appearances and by their electrophysiological responses to ET-1. Whereas the spontaneous pacing rate and the PMP slope were similarly decreased by ET-1 (10 nm) in both cell types, ET-1 depolarised MDP from −67 ± 1 to −62 ± 4 mV in spindle-shaped cells but hyperpolarised it from −73 ± 1 to −81 ± 3 mV in rod-shaped cells. ET-1 decreased APD50 by 8 and 52 % and shifted the take-off potential by +5 and −9 mV in spindle- and rod-shaped cells, respectively.ET-1 decreased the high-threshold calcium current (ICaL) by about 50 % in both cell types, without affecting its voltage dependence, and decreased the delayed rectifier K+ current (IK) with significant shifts (of +4.7 and +14.0 mV in spindle- and rod-shaped cells, respectively) in its voltage dependence. It was exclusively in rod-shaped cells that ET-1 activated a sizeable amount of time-independent inward-rectifying current.The hyperpolarisation-activated current (If), observed exclusively in spindle-shaped cells, was significantly increased by ET-1 at membrane potentials between −74.7 and −84.7 mV whereas it was significantly decreased at more negative potentials. ET−1 significantly decreased the slope of the current-voltage (I–V) relation of the If tail without changing its half-maximum voltage.The overall negative chronotropic influence of ET-1 on the whole rabbit SAN is interpreted as resulting from the integration of its different actions on spindle- and rod-shaped SAN cells through electrotonic interaction