International Journal of Food Engineering

Vapour Transport Mechanism in Osmotic Distillation Process

Ratchaneekorn Thanedgunbaworn — Fri, 20 Nov 2009 14:17:08 PST

Osmotic distillation experiments were carried out using pure water as feed in order to investigate the mass transfer mechanism in the membrane. In the experiment, the hollow fibre modules with packing density of 30.6 and 61.2% were employed. The Dusty gas model was used to estimate the transport of vapour through the membrane. The results revealed that the water vapour transport in the membrane pores in this study followed the Knudsen-molecular diffusion transition model. The value of membrane mass transfer coefficient evaluated by the transition model was found to be 0.863 kg/m2.h.Pa which was in good agreement with the experimental value. The packing density of the module did not affect the membrane mass transfer coefficient. On the other hand, the membrane mass transfer coefficient depended on the temperature.

Rapid Detection Techniques for Biological and Chemical Contamination in Food: A Review

Yali Tang — Thu, 12 Nov 2009 13:03:13 PST

The contamination problem in food safety is still a major concern not only for developing countries but also for the industrialized world. To guarantee the food safety, the advanced examination technique is needed urgently. However, the traditional methods have some typical drawbacks which include: high costs of implementation, long time of analysis and low samples throughput, and the need for high qualified manpower. The availability of fast, reliable and simple to use detecting tools for food products is therefore a target both for the safeguard of customer's health and production improvement. This article overviews the progress of the rapid detection methods for biological and chemical contamination in food.

Use of Cassava Peel as Carbon Source for Production of Amylolytic Enzymes by Aspergillus niveus

Tony Marcio Silva — Tue, 03 Nov 2009 14:26:11 PST

Aspergillus niveus produced high levels of α-amylase and glucoamylase in submerged fermentation using the agricultural residue cassava peel as a carbon source. In static conditions, the amylase production was substantially greater than in the agitated condition. The optimized culture conditions were initially at pH 5.0, 35�C during 48 hours. Amylolytic activity was still improved (50%) with a mixture of cassava peel and soluble starch in the proportion 1:1 (w/w). The crude extract exhibited temperature and pH optima approximately 70�C and 4.5, respectively. Amylase activity was stable for 1 h at 60�C, and at pH values between 3.0 and 7.0. The enzyme hydrolysed preferentially maltose, starch, penetrose, amylose, isomaltose, maltotriose, glycogen and amylopectin, and not hydrolysed cyclodextrin (α and �), trehalose and sucrose. In the first hour of reaction on soluble starch, the hydrolysis products were glucose and maltose, but after two hours of hydrolysis, glucose was the unique product formed, confirming the presence in the crude extract of an α-amylase and a glucoamylase.

Recognition and Classification of Food Grains, Fruits and Flowers Using Machine Vision

Dayanand G. Savakar — Wed, 28 Oct 2009 19:58:30 PDT

In this paper, we have presented different methodologies devised for recognition and classification of images of agricultural/horticultural produce. A classifier based on BPNN is developed which uses the color, texture and morphological features to recognize and classify the different agricultural/horticultural produce. Even though these features have given different accuracies in isolation for varieties of food grains, mangoes and jasmine flowers, the combination of features proved to be very effective. The average recognition and classification accuracies using colour features are 87.5%, 78.4% and 75.7% for food grains, mango and jasmine flowers, respectively, and the average accuracies have increased to 90.8%, 80.2% and 85.8% for food grains, mangoes and jasmine flowers ,respectively, using texture features. The average accuracies have increased to 94.1%, 84.0% and 90.1% for food grains, mangoes and jasmine flowers, respectively. The results are encouraging and promise a good machine vision system in the area of recognition and classification of agricultural/horticultural produce.

Modeling and Optimization of the Sugar Extraction Process

Rahmat Sotudeh-Gharebagh — Wed, 07 Oct 2009 23:25:17 PDT

In this work, a mathematical model is first developed for the sugar extraction process under steady state conditions. The process takes place in a vertical tower in which hot water and beet cossettes are entered counter currently and the juice is enriched with sugar. The amount of sugar extracted and also the amount of sugar loss at the exit would be increased by an increase in the tower length, the beet residence time or the amount of fresh water consumed. However, this would lead to an increase in the amount of non-sugars within the extractor which is highly undesirable and requires much more in operating costs. To avoid this, the tower length and beet residence time should be at their optimal values in addition to draft, which is the percent ratio of raw juice extracted to the beet processed. This study determines these optimal values in a way to minimize the total operating costs based on the mathematical model using the genetic algorithm method. The results of this study can be used as a framework to optimize the performance of industrial extractors.

Production of Shelf-Stable Annurca Apple Juice with Pulp by High Pressure Homogenization

Francesco Dons� — Tue, 06 Oct 2009 17:43:37 PDT

Annurca apple juice was processed by high pressure homogenization (HPH) to inactivate the endogenous microbial flora, with the aim of maintaining the organoleptic properties and the polyphenolic content of the fresh juice. In particular, it was shown that the shelf life of clear juice can be prolonged for many weeks of storage both at 4�C and 37�C upon HPH treatment at 250 MPa. Instead, the juice with pulp required higher pressure levels (300 MPa) for microbial stabilization both at 4�C and 37�C. The sample stored at 37�C exhibited a physical instability, with deviation in color and pH, which reduced the shelf life, but the samples stored at 4�C exhibited an excellent microbial stability and no observable variation of pH and color, suggesting that HPH can represent a good option for non thermal pasteurization of Annurca apple juice.Interestingly, the HPH treatment delivered also significant changes to the distribution of suspended particles, whose comminution had a measurable effect on viscosity.

3-D Imaging of Deep-Fat Fried Chicken Nuggets Breading Coating Using X-Ray Micro-CT

Akinbode A. Adedeji — Tue, 22 Sep 2009 05:38:55 PDT

Food coatings are used to add value to deep-fat fried foods and to control heat and mass transfer during frying. They impart special characteristics such as crispiness and flavor to fried products while they also form a barrier to moisture and fat transfer during frying. Development of structure during frying plays an important role in defining the performance of batter/bread coatings. Food structural properties such as porosity have been associated with fat uptake in fried foods. A good understanding of the microstructural properties is necessary in order to produce high quality fried foods. X-ray micro-computed tomography (X-ray micro-CT) is a unique technique for imaging food non-invasively, requiring no or minimal sample preparation and 3-D rendition of high resolution images. The technique is capable of providing morphological details under a natural environment, which gives some advantages over the conventional imaging techniques such as microscopy. Study on chicken nuggets provided useful information relating frying conditions to structural changes in the breading-batter coating using X-ray micro-CT technique. Chicken nuggets were fried at 180�C for different frying durations after which the products were scanned using X-ray micro-CT. Images were reconstructed and analyzed, and 2-D and 3-D renditions of the coating images confirmed porosity changes with frying time. Numerical slicing of the 3-D images with image analysis software showed the degree of interconnectivity of pores, pore shape and pore count under different conditions of frying. The effect of frying time on microstructural parameters is significant. X-ray micro-CT shows great prospect in characterizing microstructural properties of foods especially coated fried products. This technique could be used in optimizing mass transfer during deep-fat frying by providing quantitative information on structural properties such as porosity, pore size distribution and pore connectivity.

Effects of Flaxseed Gum Addition and Drying Conditions on Creep-Recovery Properties and Water Vapour Transmission Rate of Starch-Based Films

Xin-yu Li — Tue, 22 Sep 2009 05:38:51 PDT

This study investigated the effect of different concentrations of flaxseed gum (0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%) and various drying conditions (40 �C, 60 �C, 80 �C) on creep-recovery property and water vapor transmission rate (WVTR) of a starch-based films composed of cornstarch, flaxseed gum and glycerol. In creep-recovery tests, the data were modeled by Berger model. Results showed that E₂ and η₁ of different flaxseed gum concentrations all decreased with an increase of flaxseed gum concentration first and then increased in both creep and recovery tests. Increasing drying temperature decreased E₂ and η₁ in both creep and recovery tests. The addition of flaxseed gum increased WVTR compared with the flaxseed gum free sample. Films under different drying conditions displayed similar WVTR.

Model of Steam and Water Extraction of Essential Oil of Eucalyptus Citriodora Using a Complete 2n Factorial Plan

Thomas Silou — Tue, 08 Sep 2009 16:32:04 PDT

The steam and water distillation of leaves of Eucalyptus citriodora was modeled using a complete 2n factorial plan. Eight experiments were carried out, with three easily interpretable variables, for steam distillation and for a first degree polynomial model. The average essential oil yield was 2.3%. Positive effects decreased in the order: duration of the extraction, heating power and state of division of the plant. Interactions were negligible. Extraction conditions had no practical impact on citronellal content, which yielded an average content of 83.26% with a range of 80.2-85.4%. Weak negative effects were observed on duration of heating and state of division of plant material. Sixteen experiments were conducted on four variables for water distillation. The extracted essential oil yield was increased by 28%. Effects on citronellal content were the same as with steam extraction. Hence, water distillation is better suited for small-scale extraction given the simplicity of the equipment required and the significant gain in extraction yield.

Pulsed Infrared Roasting of Groundnuts and its Quality

Sanjeet Kumar — Wed, 26 Aug 2009 17:46:08 PDT

The application of high intensity, pulsed infrared radiation for roasting of groundnuts is attempted and the product quality is compared with that of the conventionally roasted samples. Product qualities such as lightness (color), compressive strength (texture) and free fatty acid content are analyzed for different combinations of roasting duration (4-12 min) and temperature (160-200�C), selected based on central composite rotatable design (CCRD). Pulsed infrared roasting at 178-188�C for 6.8-9.2 min resulted in optimum product quality in terms of color, texture and free fatty acid content. The other parameters such as oil and moisture content, peroxide value and sensory characteristics of roasted nuts are also evaluated for the select temperature-duration combinations. The oil yield increased marginally with roasting duration and temperature. Peroxide number, an indicator of the stability of fat, did not vary during infrared roasting. Groundnuts processed at 180�C for 8 min scored high in terms of sensory attributes. Infrared roasting resulted in better product quality as compared to drum and sand roasting.