Montira Nopharatana

Gamma-linolenic acid production of Mucor rouxii by solid-state fermentation using agricultural by-products

Aims:  This study aims to maximize the yield of gamma‐linolenic acid by a filamentous fungus, Mucor rouxii, using low cost production by solid‐state fermentation.

The Bioreactor Step of SSF: A Complex Interaction of Phenomena

As argued in Chap. 1, mathematical models of bioreactor operation will be important tools in the development of bioreactors for solid-state fermentation (SSF) processes. These mathematical models must describe quantitatively the various phenomena within the SSF process that can potentially limit the performance of the bioreactor. One of the key early steps in modeling is to identify what these phenomena are, and to unite them in a qualitative description of the system, at an appropriate level of detail (an idea that will be developed further in Chap. 13). The current chapter provides a basis for this by describing SSF processes qualitatively, from several different perspectives. The current chapter presents:

Mathematical Modeling of Biomass and Enzyme Production Kinetics by Aspergillus niger in Solid-State Fermentation at Various Temperatures and Moisture Contents

The effect of temperature and substrate moisture content on the growth and production of amylase, protease and phytase by Aspergillus niger during solid-state fermentation was investigated. A mathematical model regarding the kinetics of growth and enzyme production was performed to calculate the parameters at different temperatures and substrate moisture contents. The growth kinetics of A. niger could be described by the logistic growth model; the mathematical modeling parameters regarding maximum specific growth rate (μmax) and maximum biomass concentration (Xmax) were obtained by fitting the experimental data to the logistic model. The enzyme production kinetics could be described by the Luedeking-Piret model. The mathematical modeling parameters which included the growth-associated formation constant of the product i (αi) and the non-growth-associated formation constant of the product i (βi) were calculated. The production of amylase, protease and phytase was shown to be exclusively growth-associated. The effect of temperature on μmax, Xmax and αi could be described by the cardinal temperature model with inflection (CTMI). Both growth and enzyme formation were clearly influenced by temperature and the optimum culture conditions for growth and enzyme production by A. niger were determined to be approximately 34°C with a substrate moisture content ranging from 40 to 60%.

Reduction of the polycyclic aromatic hydrocarbon (PAH) content of charcoal smoke during grilling by charcoal preparation using high carbonisation and a preheating step

ABSTRACT Charcoal-grilling may lead to contamination of food with carcinogenic polycyclic aromatic hydrocarbons (PAHs) during the grilling process. The objective of this work was to determine the effect of charcoal preparation on 16 USEPA priority PAHs in the smoke produced during the grilling process. Firstly, mangrove charcoal was prepared at carbonisation temperatures of 500, 750 and 1000°C. The charcoal were then preheated by burning at 650°C. This preheating step is usually used to prepare hot charcoal for the grilling process in the food industry. In this study, charcoal was preheated at different burning times at 5, 20 min and 5 h, at which time partial and whole charcoal glowed, and charcoal was completely burnt, respectively. Finally, PAHs in the smoke were collected and determined by GC/MS. The result showed that charcoal prepared at a carbonisation temperature of 500°C had higher levels of PAHs released into the smoke. In contrast, charcoal produced at 750 and 1000°C had lower PAHs released for all burning times. In addition, PAHs released for 5, 20 min and 5 h of burning time were about 19.9, 1.2 and 0.7 µg g−1 dry charcoal for charcoal produced at 500°C, and about 0.9–1.4, 0.8–1.2 and 0.15–0.3 µg g−1 dry charcoal for charcoal produced at 750 and 1000°C, respectively. Therefore, this research suggests that food grilled using charcoal carbonised at a high temperature of about 750°C presents a lower risk of PAH contamination. In addition, in the preheating step, whole charcoal should fully glow in order to reduce the PAH content in charcoal before grilling.

Development of an Oscillating Drum Granulator Prototype for Cassava Pearl

This paper presents an oscillating drum granulator prototype for cassava pearl. Effects of filling degree and oscillating speed on cassava pearl granulation were investigated. A stainless steel drum granulator with 50 cm diameter and 16 cm length was developed. The stainless steel joints with a cotton-transmitting belt were used to connect the drum to an oscillator arm to simulate the flexibility of a traditional cloth cradle granulator. The filling degree and oscillating speed were varied from 1, 2 and 3 kg and from 87 and 100 rpm, respectively. During granulation, samples were taken at 4, 8, 12 and 16 minutes to determine the particle size distribution, mass mean diameter, granule density, hardness and sphericity. The results indicated that both the filling degree and oscillating speed played an important role on cassava pearl granulation. The filling degree of 3 kg and oscillating speed of 100 rpm was suggested since it yielded similar properties of cassava pearls to those obtained from the traditional process. This prototype granulator could successfully produce 2.4-mm pearls with comparable characteristics to the standards. Comparing to a traditional granulator, the oscillating drum granulator is easier to clean and more GMP compliant.

Effects of Pneumatic Conveying Drying Conditions on Damaged Starch Content and Particle Size of Cassava Starch

This research aimed to investigate the effects of pneumatic conveying drying conditions on damaged starch content and particle size of cassava starch using response surface methodology. Three parameters of interest, i.e. drying air temperature (120, 160, and 200oC), drying air velocity (20, 30, and 40 m/s), and feed moisture content (40, 50, and 60% d.b.), were varied. Experimental results showed that damaged starch content and average particle size of cassava starch before drying were approximately 0.45% and 21.47µm, respectively. However, after drying, the values were altered to approximately 0.69 to 6.84% and 15.40 to 31.67 µm, respectively. The drying air temperature, drying air velocity, and feed moisture content significantly affected the changes. The results indicated that cassava starch granules were damaged and then agglomerated into large particle during pneumatic conveying drying depending on operation conditions.