Determination Of The Mass Transfer Characteristic Of Thermal Drying And Osmotic Dehydration Of Pumpkin And Bitter Leaf

Project and Seminar Material for Microbiology

Determination Of The Mass Transfer Characteristic Of Thermal Drying And Osmotic Dehydration Of Pumpkin And Bitter Leaf


Abstract


The experiment was carried out and three osmotic solutions were prepared, “hypertonic solution 60% concentrated, hypotonic solution 40% concentrated and isotonic solution 50% concentrated” and oven drying was also carried in the course of the experiment, the effect of sodium chloride (osmotic agent) concentration, temperature and immersion time on overall mass transfer coefficient, effective diffusivity, drying rate weight loss and shrinkage ratio on oven drying and osmotic dehydration of Pumpkin and bitter leaf. Results showed that both pumpkin and bitter leaf had a highest mass transfer coefficient in oven drying at highest temperature of 80oC, for pumpkin leaf 0.149(m/min), bitter leaf was 0.149(m/min), the results were also obtain for osmotic dehydration at 80Oc at highest concentration (Hypertonic solution) had the highest mass transfer coefficient, for pumpkin leaf was 0.015(m/min) for bitter leaf was obtained to 0.032(m/min).

For osmotic dehydration, both samples weight loss percent (WL%) for hypertonic solution at 800C for 90mins had the highest weight loss percent, but the shrinkage ratio decrease with increase in time.The mass transfer during oven drying of pumpkin and bitter leaf was described using Fickian equation of diffusion with drying taking place in the falling rate period, the effective moisture diffusivity value showed temperature dependence on both samples. Effective diffusivity values were also determined for oven drying at different temperature, and the values increases as the temperature increases, for pumpkin and bitter leaf at 600C, 700C and 800C, the effective diffusivities were 1.0E-09, 1.87106E-09 and 2.1843E-09m2/min and 8.52966E-10, 1.00015E-9 and 2.45308E-08m2/min.


Table of Contents


  • Title Page
  • Certification
  • Dedication
  • Acknowledgement
  • Table of Content
  • List of Figure
  • List of Tables
  • Abstract:

Chapter One:

Introduction

  • 1.1 Background:
  • 1.2 Mass Transfer Phenomena During Osmotic Dehydration:
  • 1.3 Condition for Drying
  • 1.4 Statement of the Research Problem:
  • 1.5 Propose Solution
  • 1.6 Aim
  • 1.7 Objectives of the Study:
  • 1.8 Relevance of Study
  • 1.9 Method and Scope

Chapter Two:

Literature Review

  • 2.1 General Over View
  • 2.2 Basic Terminology in Drying Terms:
  • 2.2.1 Adiabatic Saturation Temperature
  • 2.2.2 Bound Moisture
  • 2.2.3 Constant Rate Drying Period:
  • 2.2.4 Dew Point:
  • 2.2.5 Drying Bulb Temperature
  • 2.2.6 Equilibrium Moisture Content:
  • 2.2.7 Critical Moisture Content
  • 2.2.8 Falling Rate Period:
  • 2.2.9 Free Moisture
  • 2.2.10 Humid Heat
  • 2.2.11 Absolute Humidity
  • 2.2.12 Relative Humidity
  • 2.2.13 Unbound Moisture
  • 2.2.14 Water
  • 2. 2.15 Wet Bulb Temperature:
  • 2.3 Advances in Food Drying
  • 2.3.1 Uses of Advanced Computational Tools:
  • 2.4 Quality Change During Drying:
  • 2.4.1 Browing:
  • 2.4.2 Case Hardening:
  • 2.4.3 Rehydration
  • 2.5 Classification of Industrial Dryers
  • 2.5.1 Conduction and Convection Dryer
  • 2.5.2 Radiation and Convection Dryers
  • 2.6 Description of Dryer
  • 2.6.1 Tray Dryer
  • 2.6.2 Band (Belt) Dryers
  • 2.6.3 Rotary Dryers
  • 2.6.4 Roller Dryers
  • 2.6.5 Fluidized Bed Dryers
  • 2.6.6 Spray Dryers
  • 2.7 Osmotic Dehydration
  • 2.8 Application of Osmosis in Food Processing:
  • 2.9 Parameters Influencing the Osmotic Process
  • 2.10 Raw Materials Characteristics for Osmotic Dehydration:
  • 2.10.1 Quality of Raw Material
  • 2.10.2 Shape, Size and Thickness of the Fruit Pieces
  • 2. 11 Type of Osmotic Agent
  • 2.12 Contacting Time:
  • 2.13 Osmotic Process Parameter
  • 2.13.1 Immersion Time
  • 2.13.2 Temperature of the Osmotic Solution
  • 2.13.3 Concentration of Osmotic Solution
  • 2.13.4 Agitation / Circulation
  • 2.13.5 Fruit Pieces to Osmotic Solution Ratio:
  • 2.14 Kinetic of Osmotic Dehydration
  • 2.15 Mass Transfer Phenomena During Osmotic Dehydration
  • 2.16 Drying Behavior of Osmotic Concentrated Fruits
  • 2.17 Packaging of Osmotic Dehydrated Products
  • 2.18 Storage of Osmotic Dehydrated Products
  • 2.19 Microbial Studies of Osmotic Dehydrated Products
  • 2.20 Advantages of Osmotic Dehydration

Chapter Three:

Apparatus / Equipment and Methodology

  • 3.1 Osmotic Dehydration
  • 3.2 Method of Osmotic Dehydration
  • 3.3 Oven Drying
  • 3.4 Method of Oven Drying
  • 3.5 Moisture Ratio (MR)
  • 3.6 Estimation of Effective Diffusivity
  • 3.7 Drying Model

Chapter Four:

Result and Discussion

  • 4.1 Water Loss (Wl%) During Osmotic Dehydration of the Samples
  • 4.2 Mass Shrinkage Ratio During Osmotic Dehydration of the Samples
  • 4.3 The Mass Transfer Coefficient During Osmotic Dehydration
  • 4.4 Oven Drying
  • 4.5 The Mass Transfer Coefficient During Oven Drying

Chapter Five:

Conclusion and Recommendation

  • 5.1 Conclusion
  • 5.2 Recommendation
  • Reference
  • Appendix

List of Figure


  • Fig 1: Response of Weight Loss (Wl%) to Different Solute Concentration and Immersion Time for Dehydration of Bitter Leaf:
  • Fig 2: Response of Weight Loss (Wl%) to Different Solute Concentration and Immersion Time for Dehydration of Pumpkin Leaf:
  • Fig3: Response of Mass Shrinkage Ratio (Sr) to Different Solute Concentration and Immersion Time for Dehydration of Bitter Leaf:
  • Fig4: Response of Mass Shrinkage Ratio (Sr) to Different Solute Concentration and Immersion Time for Dehydration of Pumpkin Leaf:
  • Fig5: Effect of Moisture Content on Drying Rate at Different Temperatures for Pumpkin Leaf
  • Fig6: Of Moisture Content on Drying Rate at Different Temperatures for Bitter Leaf
  • Fig7: Effect of Moisture Ratio in(Mr) With Time Respect With Temperature for Pumpkin Leaf
  • Fig8: Effect of Moisture Ratio in(Mr) With Time Respect With Temperature for Pumpkin Leaf
  • Fig9: Effect of Moisture Ratio With Time Respect With Temperature for Bitter Leaf
  • Fig10: Effect of Moisture Ratio With Time Respect With Temperature for Pumpkin Leaf

List of Tables


  • Tab 1: The Mass Transfer Coefficient of Bitter Leaf During Osmotic Dehydration (Hypertonic Solution)
  • Tab 2: The Mass Transfer Coefficient of Bitter Leaf During Osmotic Dehydration (Hypotonic Solution)
  • Tab 3: The Mass Transfer Coefficient of Bitter Leaf During Osmotic Dehydration (Isotonic Solution)
  • Tab 4: The Mass Transfer Coefficient of Pumpkin Leaf During Osmotic Dehydration (Hypertonic Solution)
  • Tab 5: The Mass Transfer Coefficient of Pumpkin Leaf During Osmotic Dehydration (Hypotonic Solution)
  • Tab 6: Mass Transfer Coefficient of Pumpkin Leaf During Osmotic Dehydration (Isotonic Solution)
  • Tab 8: Effective Diffusivity of Pumpkin Leaf at Different Temperature
  • Tab 9: Effective Diffusivity of Bitter Leaf at Different Temperature
  • Tab 10: R2 and K Constant Value of Lewis Model for Oven Drying of Pumpkin Leaf
  • Tab 11: R2 and K Constant Value of Lewis Model for Oven Drying of Bitter Leaf
  • Tab 12: The Mass Transfer Coefficient During Oven Drying of Pumpkin Leaf at Different Temperature
  • Tab 13: The Mass Transfer Coefficient During Oven Drying of Bitter Leaf at Different Temperature

Chapter One


1.0 Introduction

1.1 Background

Fruits and vegetables contribute a crucial source of nutrients in daily human diet, the world fruit production is estimated to be 434.7 million metric tones and vegetables 90.0 million metric tones. India is the second largest fruits and vegetable producer and its annual production is 44 million metric tones from an area of 3, 949, 000 haduring 2000-2002 (Srivastava& Kumar, 2002). Fruits and vegetables losses in the developing countries are considerably high. In India, post harvest losses of fruits and vegetables are estimated as more than 25 percent. Many processing techniques can be employed to preserve fruits and vegetables by drying and dehydration is one of the most important operations that are widely practiced because of considerable saving in packaging, storageetc

Vegetables contain nearly 70% to 95% of moisture which make them highly perishable. If this moisture is reduced to some extent, bulk transportation of the final product can be made to other parts of the country where it is not available. Also the shelf life of the product is increased. Conventionally sun drying and hot air drying is used to dry and preserve the product. This produced discolored and shrieked products which were of not interest to patronage. When osmotic dehydration is used prior to drying steps it is evident that it conserves energy and reduces the heat damage to the product in terms of color, flavor and aromaetc

Osmotic dehydration aims at extending life of food by removing water without phase transition [Kowalska and Lenart 2001, Matuska et al. 2006]. The process is carried out by immersing the raw material in a hypertonic solution (solution with high concentration of sugars, sodium chloride, etc.).

Osmotic dehydration is used for foods with a tissue structure, such as shredded fruit and vegetables [Torreggiani 1993]. The method is based on the natural phenomenon of osmosis through cell membranes of biological material [Shi and Le Maguer 2002]. In the osmotic dehydration the process of water flow to the outside of food material takes place, and entering of substances dissolved in a hypertonic solution into the product. Since the cell membrane is not perfectly selective, the solutes present in cells (organic acids, sugars, minerals, fragrances, and colorants) can pass with water into the hypertonic solution [Derossi et al. 2008].


1.2 Mass Transfer Phenomena During Osmotic Dehydration

There are three major types of counter current mass transfer in osmotic concentration process (Karthiayani, 2004;Tiwari, 2005) (Figure 2).

  1. Important water out flow from product to solution.
  2. A solute transfer, from the solution to the product; it makes thus possible to introduce the desired amount of an active principle, a preservative agent, any solute or nutritional interest, or a sensoryquality improvement of the product.
  3. Leaching out of products own solutes (sugar, organic acids, minerals, vitamins etc.), which is quantitatively negligible when compares with the first two types of transfer, but essential with regard to the composition of final product

Drying of fruits and vegetables such as pumpkin, fruit pepper and bitter leaves e.t.c is one the most time and energy consuming process in the modern food industry [sunjka et al 20004]. However these fruit and vegetable are usually in short supply during dry season because they are perishable crops which deteriorate within a few days after harvest (which occur mainly in rainy season). Preserving these crops in their fresh state for months has been a problem that is yet unsolved [famurewa et al 2006; Agarryetal 2006].

Drying processes play an important role in the preservation of agricultural products. They are defined as a process of moisture removal due to simultaneous heart and mass transfer in which energy must be supplied [waewsak et al 2006]


1.3 Conditions for Drying

The general condition include the following:

  1. Heat is transfer by evaporation of liquid or moisture from the surface of the solid
  2. Mass is equally transferred

1.4 Statement of the Research Problem

Most of the work done on this subject have been on the change that occur in the nutritional properties and mass transfer at different temperature, immersion time and concentration of the solution


1.5 Propose Solution

This works tends to do proper investigation on the drying rate and mass transfer characteristic in different osmotic solution and thermal drying of vegetable to bring it to the awareness of the public, this work tends to bring out the importance of choosing the best optimum temperature and best osmotic solution for thermal drying and osmotic dehydration


1.6 Aim of Study

The aim of this research work is to investigate the mass transfer characteristic of pumpkin and Bitter leaf


1.7 Objectives of the Study

The following objectives were use to achieved the aim.

  1. To investigate the effect of temperature on drying rate of pumpkin and bitter leaf
  2. To investigate the effect of osmotic concentration of pumpkin and Bitter leaf
  3. To investigate the effect of time for drying rate and osmotic dehydration for Pumpkin and Bitter leaf
  4. To determine the optimum condition of thermal drying and osmotic dehydration.

1.8 Relevance of Study

This is necessary to determine the suitability of the drying process that will help in mass transfer, and it also provide a suitable method that will help reduce crop loss in Nigeria.


1.9 Method and Scope

The method used in this work include;

  1. Osmotic solution (hypertonic, Isotonic and hypotonic solution) using NaCL as the osmotic agent , were prepared at different temperature interval the solution was stirred until complete dissolution, the samples were pumpkin and bitter leaf
  2. Samples of pumpkin and bitter leaves were weight and spread on a metal tray which was then place in a laboratory oven. The drying was carried out at different temperature of 600C, 700C and 800C
  3. The effective diffusivity was determine by using fickian equation

The scope of this research is limited to the study of mass transfer coefficient during thermal drying and osmotic dehydration of pumpkin and Bitter leaf


Chapter Five


Conclusion and Recommendation

5.1 Conclusion

The drying characteristic of pumpkin and Bitter leaf were carried out by using osmotic dehydration and thermal drying. Based on my finding , the overall mass transfer coefficient of osmotic dehydration and Oven drying were concluded that solute (NaCL) concentration (Hypertonic solution) to increase in overall mass transfer coefficient, also as at temperature of (80oC) both contributes significantly to osmotic dehydration of pumpkin and Bitter leaf, and the highest value of weight loss was obtain at Hypertonic solution at 800C in 90mins also shrinkage ratio decreases with increase in immersion time on the experiment

From the result for oven drying it can be concluded that temperature was found to be main factor influenced the mass transfer of pumpkin and bitter leaf, at high temperature from 600C___ 800C moisture diffusion of both pumpkin and bitter leaf increased, the lowest moisture diffusion for pumpkin and bitter leaf was 1.0E-09m2/min and 8.52966E-10m2/min whilst its maximum diffusivity were 2.1843E-09m2/min and 2.45309E-08m2/min


5.2 Recommendation

As recommendation that can help in future studies in the osmotic dehydration and thermal drying of vegetables and fruits, because, like osmotic dehydration have potential advantages of less heat damage, good blanching effect, less enzymatic browning , better retention of flavor and energy saving because no phase change, researcher should put this into consideration because most industrial application, and technical economy studies, more food processors are applying this new technique to improve product quality and increase market potential also for the oven drying recommended those parameter that might effect the rate of diffusivity and mass transfer coefficient of our finding would be properly control


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