Spray Drying Techniques for Food Ingredient Encapsulation

C. Anandharamakrishnan, Padma Ishwarya S.

• Publisher: Wiley-Blackwell
• Year: 2015
• Print ISBN: 9781118864197
• eBook ISBN: 9781118864074
• Edition: 1
• Topic: Technik & Maschinenbau
• Subtopic: Lebensmittelwissenschaft

Spray drying is a well-established method for transforming liquid materials into dry powder form. Widely used in the food and pharmaceutical industries, this technology produces high quality powders with low moisture content, resulting in a wide range of shelf stable food and other biologically significant products. Encapsulation technology for bioactive compounds has gained momentum in the last few decades and a series of valuable food compounds, namely flavours, carotenoids and microbial cells have been successfully encapsulated using spray drying.

Spray Drying Technique for Food Ingredient Encapsulation provides an insight into the engineering aspects of the spray drying process in relation to the encapsulation of food ingredients, choice of wall materials, and an overview of the various food ingredients encapsulated using spray drying. The book also throws light upon the recent advancements in the field of encapsulation by spray drying, i.e., nanospray dryers for production of nanocapsules and computational fluid dynamics (CFD) modeling.

Addressing the basics of the technology and its applications, the book will be a reference for scientists, engineers and product developers in the industry.

1
Introduction to spray drying

1.1 INTRODUCTION

“The process of simultaneously atomizing and desiccating fluid and solid substances, and its application to the purpose of the exhaustion of moisture from such substances, and for the prevention of destructive chemical change.”

Samuel R. Percy (1872)

The above words are excerpts from the first ever detailed description of a drying technique, which is now well-known and appreciated as “Spray Drying”. Spray drying is a 140 years young and flourishing drying technique. Throughout all these years, this perpetual process has exhibited an ebullient growth, imbibing innumerable innovations in terms of its operational design and widely varied applications.

Spray drying has its origin in the United States, since the first patented design was registered there in 1872. World War II was a significant chronological event in the history of spray drying, monopolizing the process in the dairy industries for continuous production of milk powder. Since then, the process has adapted itself to a number of design modifications, and today has evolved as an industry-friendly drying technique. Spray drying stands out from other processes involving liquid drying by its ability to handle feedstock of varying nature, producing flowing powders of specific particle size, high productivity and versatile applications.

By definition, “Spray drying is the transformation of feed from a fluid state into a dried particulate form by spraying the feed into a hot drying medium.” (Masters, 1991)

A spray dryer operates on convection mode. The principle of working is moisture removal by application of heat to the feed product and controlling the humidity of the drying medium. Here, the uniqueness is that the evaporation of moisture is promoted by spraying the feed into a heated atmosphere, resulting in improved drying rate. The mechanism can be better understood, when the spray drying process is divided into its constituent unit operations.

A liquid feed entering the spray dryer undergoes a series of transformations before it becomes powder. The changes are due to the influence of each of the four stages (Figure 1.1) involved in spray drying, namely:

1. Atomization of the feed solution.
2. Contact of spray with the hot gas.
3. Evaporation of moisture.
4. Particle separation.

Figure 1.1 Process steps of spray drying. (1) Atomization. (2) Spray – hot air contact. (3) Evaporation of moisture. (4) Product separation.

Each of the above exerts influence on the final product quality. Understanding the process steps, along with the hardware systems involved in it, will enable visualization of the operation on a glimpse of a reading. Hence, subsequent sections will narrate in detail each of the abovementioned unit operations, with a description of the associated hardware components.

1.2 STAGE 1: ATOMIZATION

Atomization is the heart of spray drying, and is the first transformation process that the feed undergoes during spray drying. Although several definitions of atomization exist, one of the initial definitions of the process, by Samuel Percy, is as interesting as it is precise: “bringing fluid or solid substances into a state of minute division”. The breakup of bulk liquid into a large number of droplets drives the rest of the spray drying process by reducing the internal resistances to moisture transfer from the droplet to the surrounding medium. This is because of the enormous increase in surface area of the bulk fluid as the droplet fission proceeds, with its instability increasing in accordance with the intensity of atomization.

Atomization is central to the spray drying process, owing to its influence on shape, structure, velocity and size distribution of the droplets and, in turn, the particle size and nature of the final product. A cubic meter of liquid forms approximately 2 × 10¹² uniform 100 micron-sized droplets, offering a total surface area of over 60,000 m² (Masters, 2002). This greater surface-to-volume ratio enables spray drying to achieve a faster drying rate (as drying time is proportional to the square of the particle dimension). Consequently, there is minimal loss of heat sensitive compounds and, eventually, particles of the desired morphology and physical characteristics are obtained.

1.2.1 Principle of atomization

The working principle of the atomizers is governed by the liquid disintegration phenomenon explained by several researchers. It is worth understanding the progression in the concepts on atomization phenomenon across the years. This will also help in appreciating the science of droplet formation from an atomizer.

Joseph Plateau was the first to characterize liquid instability in 1873, through his experimental observations. A liquid jet, initially of constant r...

Table of contents

• Cover
• Title Page
• Table of Contents
• About the authors
• Preface
• Acknowledgments
• 1 Introduction to spray drying
• 2 Introduction to encapsulation of food ingredients
• 3 Spray drying for encapsulation
• 4 Selection of wall material for encapsulation by spray drying
• 5 Encapsulation of probiotics by spray drying
• 6 Encapsulation of flavorsand specialty oils
• 7 Encapsulation of bioactive ingredients by spray drying
• 8 Spray drying for nanoencapsulation of food components
• 9 Functional properties of spray dried encapsulates
• 10 Analysis of spray dried encapsulates
• 11 Modeling approach for spray drying and encapsulation applications
• 12 Synergistic spray drying techniques for encapsulation
• 13 Industrial relevance and commercial applications of spray dried active food encapsulates
• Index
• Advert Page
• End User License Agreement