Boon-Beng Lee

Prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method

The aim of this work was to develop prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method. The relationship between the process variables on the shape and size of the alginate drops before and after gelation was established with the aid of image analysis. The results show that a critical Ohnersorge number (Oh)>0.24 was required to form spherical beads. The shape transition of ca-alginate beads could be typically distinguished into three phases along the collecting distance and it was affected by the combined influence of the solution properties, the collecting distance and the drop size. Mathematical equations and a master shape diagram were developed to reveal a clear operating region and the overall process limits within which spherical ca-alginate beads could be formed. In terms of bead size, the overall size correction factor (K) which accounted for the liquid loss factor (k(LF)) and the shrinkage factor (k(SF)), varied between 0.73 and 0.85 under the experimental conditions. The size prediction model correlated well with the experimental data. The approach and the outcome could be used as a model to develop prediction tools for similar bead production systems.

A CRITICAL REVIEW: SURFACE AND INTERFACIAL TENSION MEASUREMENT BY THE DROP WEIGHT METHOD

The drop weight method has been used as a standard method for surface and interfacial tension measurement. However, lack of appropriate guidelines in using this method has resulted in errors. The specific objective of this critical review is to present the experimental setup, the limitations on the correction factors, and the principle of the drop weight method. Mathematical models of correction factors were evaluated by using a proposed error analysis. The use of the proposed Lee-Chan-Pogaku model and HG-Equation 2 for correction factor determination is suggested. However, further investigations would be required to justify the validity of the correction factors at low r/V 1/3 range and their use for viscous fluids. The physics of drop detachment is complicated; more investigations would be required to form a rigid theory of this method.

Surface tension of viscous biopolymer solutions measured using the du Nouy ring method and the drop weight methods

The discrepancy of the existing literature data on the surface tension values of biopolymer solutions could be affected by the measurement technique. The aim of the study was to compare the surface tension values of biopolymer solutions, measured using the du Nouy ring method and the drop weight methods (Harkins–Brown correction factors method and the LCP coefficient method). Four biopolymers were chosen (sodium alginate, carboxymethyl cellulose, xanthan gum and pectin) and the surface tensions of the solutions were measured as a function of biopolymer concentration. The surface tension was found to increase with biopolymer concentration when measured using the du Nouy ring method. On the other hand, the drop weight methods gave an opposite trend. The results verified the discrepancy of the existing literature data. The error may be caused by the correction factors calculation and the solution viscosity when the du Nouy ring method was used. The LCP coefficient method which is independent of correction factors and liquid properties is proposed for measurement of the surface tension of viscous biopolymer solutions.

Alginate liquid core capsule formation using the simple extrusion dripping method

Abstract Liquid core capsules have been widely used in various biotechnological applications. The capsules could be formed by the simple extrusion dripping method. However, the method requires strict control of several process variables in order to form spherical capsules. The aim of this study was to systematically investigate the influence of process variables of the method on the capsule size and shape. The results showed that the capsules diameter was decreased when the concentration of alginate solution was increased. The capsule diameter was increased when the gelation time and dripping tip diameter were increased. The membrane thickness of the capsules was significantly increased by the concentration of calcium chloride, gelation time and dripping tip diameter. However, the concentration of alginate gave the opposite trend on the membrane thickness of the capsules. As a recommendation, uniform and spherical alginate liquid core capsules could be formed when concentration of calcium chloride was >10 g/l, the concentration of alginate solution was >5 g/l and <20 g/l, gelation solution height in between 1.7 cm and 3.2 cm, and stirring rate of the gelation bath was in the range of 400–500 rpm.

Influence of process variables and formulation composition on sphericity and diameter of Ca-alginate-chitosan liquid core capsule prepared by extrusion dripping method

ABSTRACT The influence of process variables and formulation composition on the sphericity and diameter of the alginate capsules which contained dual cations (Ca-and-chitosan) are characterized in this study. Capsule sphericty was not influenced by needle diameter but instead, capsule diameter increased proportionally with the needle diameter. The combined effects of the liquid core solution and alginate solution on the sphericity of the capsules are tabulated. Spherical capsules can be produced when the following criteria were fulfilled: stirring speed is in the range of 240–300 rpm; calcium chloride concentration is >5 g/L; viscosity of liquid core solution is >203 mPa.s; as well as viscosity of alginate solution is in between 47 and 386 mPa.s. The capsule diameter was predicted using a modified Tate’s law equation and an error analysis was conducted to evaluate the equation. The predicted diameter was well correlated with the experimental data with an average absolute deviation <3.6%.

Diameter prediction mathematical models for xanthan gum-alginate capsules produced by extrusion-dripping method

The aim of this work is to compare the applicability of particle diameter prediction mathematical models (i.e. Tate’s Law equation, the modified Tate’s Law equation, the modified Yildirim’s model) to determine diameter of liquid core capsules. The capsules were produced by extruding xanthan gum-calcium chloride solution through a hypodermic needle into sodium alginate solution. The effects of two types of xanthan gum with different concentrations and needle diameters on capsule diameter were investigated in this work. The results showed that there was no significant difference in capsule diameter despite different types and concentrations of xanthan gum were used. However, the diameter of the capsules increased when the diameter of needles increased. As a whole, the produced capsules were in the range of 3.47 mm to 4.86 mm. Among the three studied prediction models, the modified Tate’s Law mathematical equation was the most suitable model for the diameter prediction of the liquid core capsules with AAD of...

A comparative study on liquid core formulation on the diameter on the alginate capsules

Liquid core capsule has vast application in biotechnology related industries such as pharmaceutical, medical, agriculture and food. Formulation of different types of capsule was important to determine the performance of the capsule. Generally, the liquid core capsule with different formulations generated different size of capsule.Therefore, the aim of this project is to investigate the effect of different liquid core solution formulations on the diameter of capsule. The capsule produced by extruding liquid core solutions into sodium alginate solution. Three types of liquid core solutions (chitosan, xanthan gum, polyethylene glycol (PEG)) were investigated. The results showed that there is significant change in capsule diameter despite in different types of liquid core solution were used and a series of capsule range in diameter of 3.1 mm to 4.5 mm were produced. Alginate capsule with chitosan formulation appeared to be the largest capsule among all.

Ca-Alginate Liquid Core Capsule for Lactobacili Fermentation

Lactic acid bacteria (LAB) have been used for food fermented products since ancient time, which not limited to dairy products. Some Asian traditional food is produced through LAB fermentation. LAB consist of the Gram-positive genera including lactobacillus, which produce lactic acid as the end product of a carbohydrate fermentation. Lactobacillus is one of the important LAB that have been widely applied in food fermentation because of their fermentative ability to enhance food safety, nutrition and to improve health related benefits (as probiotics bacteria). Lactobacillus also received much attention for lactic acid production. This is because lactic acid is highly demanded for the production of poly-l-lactate biodegradable plastics in recent days. The viability and microbial growth of Lactobacilli have been known to be inhibited by its end product (i.e. lactic acid). One of the common solutions to overcome the inhibition issue is by using encapsulation technology. Encapsulation offers several advantages for lactobacilli fermentation which included protection to the bacterial from harsh environments (e.g. pH, temperature, shear stress), retaining cells in continuous process, and allowing reuse of the bacteria. Encapsulation can be achieved in two forms; beads or capsules. Apart from beads, the capsules consisted of a defined inner core which surrounded by a semi permeable membrane. The content of the inner core could be in the form of liquid or solid. Liquid core capsules provide plenty of space for microbial growth (in inner core), eliminate cell release to fermentation medium and minimize mass transfer resistance of solutes. The main focus of this review was on the liquid core capsules produced by Ca-alginate bio-gel. In general, Ca-alginate liquid core capsules can be produced using single step methods or multiple steps methods. The details of the method used to produce the liquid core capsules were described and discussed. The use of the capsules for lactobacilli fermentation is limited because they are easily destabilized by chelating agents and eventually dissolved. The counter measures to strengthen the stability of the capsules were discussed. The previous studies showed that the viability, microbial growth and productivity of the encapsulated lactobacilli (in liquid core capsule) were better than those of either free cell and entrapped lactobacilli (in beads). Lastly, the authors give several recommendations to expand the potential of using the liquid core capsules to improve Lactobacilli fermentation.