Advances in Food Science and Technology (PDF)

Paper No. 16 Paper Title: Advances in Food Science and Technology Module No. 21 Module: Developments in Flavour Stabilization 21.1 Introduction Flavour is one of the most important attribute to judge the quality of food product. It is generally defined in terms of three components; odour, taste...

Paper No. 16 Paper Title: Advances in Food Science and Technology Module No. 21 Module: Developments in Flavour Stabilization 21.1 Introduction Flavour is one of the most important attribute to judge the quality of food product. It is generally defined in terms of three components; odour, taste and aroma. These components propel the popularity of food products and drive the consumers to purchase them. A person wants to buy the food that has some optimal taste on consumption. So it becomes essential to protect and control release of aroma components for desired flavour perception. But due to changes in physical and chemical properties, quality of food keep changes with time and unfortunately flavour compounds are readily lost during the storage. Starting from the raw material storage to final product development food has to undergo variety of operations which could reduce its potency and alter its flavour profile for e.g., exposure to heat, stress, moisture, presence of other solvents, ingredients etc. Flavour loss continues to occur even after post manufacturing process i.e., during transportations, post manufacturing storage and also before consumption (when food is warmed using heat). Thus in many food applications it is desirable to use some strategies to stabilize and protect the flavour to deliver it at the right time, at the right quantity and at the right rate to maintain the taste of food and hence food quality. 21. 2. Stabilisation of flavour Stabilisation of flavour is important and challenging task for food researchers. Complexation of aroma compounds can reduce the chances of flavours losses by lowering the rate of evaporation and its controlled release during the processing and storage. Researchers today actively trying to use different favourable material suitable for the better protection of flavour. Flavour is stabilised mainly for three important reasons a) Preserving and protecting the volatile or liable flavour molecules from Oxidation, Water, Evaporation, Chemically interacting species etc. b) Mask bitterness of sweeteners or reduce odour to improve factory conditions. c) Triggering and controlled release of flavours in order to achieve the better performances. (Example: flavour release in chewing gums). A large number of foods stabilisation materials are available for food industries today to retain the flavour in its actual form. For example, polysaccharides, Proteins, Fats and Fatty acids, and waxes etc. Use of hydrocolloids is most opted way suggested by researchers to overcome this problem. Table 1: List of different stabilizing material used for flavour protection. (Source: Hydrocolloids in Flavour Stabilization by Milda E. Embuscado). S.N Material Examples 1 Polysaccharides Starch, algin and alginates. Agar and agarose, pectins, carrageenan, or hydrocolloids gum Arabic, galctomannana, cellulose and cellulose derivatives (methyl and ethyl-cellulose and carboxymethyl cellulose (CMC), Maltodextrin and other gums 2 Proteins Proteins—Gelatin, casein, zein, whey, soy, and albumin. 3 Fats and fatty Mono-, di-, and triglycerides, lauric, capric, acids palmitic, and stearic acids and their salts 4 waxes Shellac, polyethylene glycol, carnauba wax, or beeswax 21. 3 Encapsulating materials The major flavour encapsulating materials which are generally used are discussed below: a) Starch : modified starch b) Gums or modified gums c) Cyclodextrin a) Modified Starch Starch is the most easily available and cheap source used for the inclusion of flavouring molecules. It is composed of amylose and amylopectin and having glucose as a structural unit. Amylose is predominately linear polymer of α-(14)-D-glucose units while amylopectin is a branched chain polymer of α-(16)-D-glucose and α-(14)-D-glucose units having different molecular weight. It is the branched structure of amylopectin which makes it highly compact thus affecting the physiochemical properties like viscosity and appearance. Amylopectin is present in all starches, constituting about 75% of most common starches.  Fig: 1: structure of amylopectin and amylase having branched and linear structure Starches offer a range of advantages over other encapsulating agents 1. Excellent emulsification and encapsulation performance 2. Low viscosity at high solids: Provides faster spray - drying rates and lower energy consumption 3. Low surface oil and excellent oxidation resistance ensures excellent flavour preservation and stabilisation of sensitive ingredients 4. Excellent stabilisation power- prevents coalescence, agglomeration and separation. Many flavours are prone to oxidation rapidly once they come in to contact of oxygen resulting in to off flavour of product. So it becomes necessary that the encapsulating material should be able to form impermeable films and fine emulsions. N-Lok a waxy maize based starch has been developed to provide the flavour industry with a product characterised by low viscosity, good emulsion qualities and enhanced oxidation barrier properties. It is able to carry and protect the flavour oil and encapsulation effectively. b) Gums and Modified Gums Gums are another class of carbohydrates used for the stabilisation of flavour because of its natural ability to produce stabilize emulsions. It is prepared from the gummy exudates flowing naturally or obtained by incision from the stems and branches of Acacia senegal and Acacia seyal trees. Gum arabic is a natural film-forming gum widely used to stabilize flavours and is also known as gum arabic. The excellent emulsification and stabilization properties of gum arabic are due to its hydrophilic carbohydrate, hydrophobic protein component, and its molecular flexibility. Gum arabic mainly consists mainly of high molecular weight polysaccharides and their salts (Ca2+,Mg2+,K+) and on hydrolysis yielded arabinose, galactose, rhamnose, and gluconic acid. The compact structure of gum Arabic is excellent for encapsulations of flavours as it emulsifies, and has low viscosity, bland flavours and protects against flavour oxidation. This low viscosity is desirable for spray drying operation. Gum arabic is pH stable and provides good retention of volatiles during spray drying. A. senegal trees are considered the best quality gum for emulsification and flavour encapsulation. Gum arabic is typically used as the gold standard or reference when evaluating a flavour encapsulation ingredient. Table 2: Different starch and gums examples. (Source: Hydrocolloids in Flavour Stabilization by Milda E. Embuscado) Examples of starch and gums encapsulating material Starch Gums Dextrinized OSAn waxy cornstarch, Gum arabic Methyl ethyl cellulose Dextrinized OSAn tapioca Modified gum arabic Sodium alginate cornstarch, Carrageenan Dextrins from cornstarch or tapioca, Guar gum OSAn waxy cornstarch Gelatin (enzymatically hydrolyzed) Carboxymethylcellulose OSAn waxy cornstarch (acid Hydroxypropyl cellulose hydrolyzed) Maltodextrins, Hydroxypropyl methyl OSAn starch + corn syrup solids Cellulose Absorbent cornstarch Methyl cellulose (OSA= octenyl succinate) c) Cyclodextrin Cyclodextrin is a enzymatically derived cyclic polymers of glucose available in (α, β, γ) forms. The unique structures of cyclodextrins enables them to form an inclusion complex, entrapping the whole or part of guest molecule inside its cavity by different binding forces such as: van der waals forces, dipole-dipole interactions and hydrogen bonding. Actually the center of cyclodextrin is hydrophobic and suitable for the hydrophobic portion of the flavour molecule. For the better encapsulation the geometry of molecule must be compatible to the structure of cyclodextrin. For example: eugenol is included very effectively into β-cyclodextrin but isoeugenol is not. Studies shows that biscuits made with butter flavour beta-cyclodextrin complex helps to retain the flavour even after two months storage as compare to control (without cyclodextrin) which lost its flavour after only two weeks and this is due to the better oxidative stability of cyclodextrin. High cost of cyclodextrin restricts its applicability in the industries as compare to other encapsulating materials available. 21.4 Techniques for flavour stabilisation The primary industrial effort to retain the flavour compounds involves the techniques given below. Owing to the wide range in techniques used for this purpose, only major processes are discussed here. a) Spray Drying b) Phase separation or coacervation processes c) Extrusion d) Molecular inclusion method e) Fluidised bed processing (coating, agglomeration) f) encapsulation a) Spray Drying The production of encapsulates can be done in many ways but spray – drying is most effective way of stabilizing and protecting the flavour. Hydrocolloids generally used in spray drying are gum acacia, modified starch or maltodextrin matrix. In this technique a homogenised mixture of solvent, flavour, and encapsulating matrix is prepared initially. Homogenisation is a critical step in that it breaks the flavour emulsion into smaller sized droplets that result in better flavour retention during the drying process. The emulsion formed helps to stabilize the liquid flavour with a thin protective layer of encapsulating agent (wall material) when the emulsion is subjected to rapid drying. The emulsion dries quickly resulting to very larger surface area to volume ratio. This encapsulating matrix (wall material) prevents volatilization and chemical  degradation and is primary determinant of oxidative stability. It improves the physicochemical and handling properties of flavour, improves its safety and textural appearance. b) Phase separation or coacervation processes This technique employs a conventional three phase system. i) Solvent: manufacturing vehicle ii) Wall material: flavour carrier iii) Core material : Flavour Principle: Coacervation is polymer complexation and colloidal system that involves the change in the thermodynamic conditions for the separation of colloidal solution in to two different liquid phases. The phase having higher colloidal concentration known as coacervate. Coacervation involves the three basic steps: 1) Formation of droplet, by emulsification of core material in gelatine or gum arabic solution. 2) Formation of wall around the droplet, by adding the above solution in to the system. 3) separation/isolation of particle. Gum Arabic or gelatine used to prepare the rich coacervate. Coacervation produces a water- insoluble capsule that has controlled release properties along with the shell structure. Then the microcapsules are collected and dried after through washing. Applications of flavour coacervates include chewing gum, instant soups and sauces, spreads, baked goods etc. Drawbacks: Require precise equipments and much expensive c) Extrusion Extrusion is another practice which is performed to encapsulate the flavour. Hydrocolloid plays a vital role in extrusion process with modified starches as carrier matrix. Once the carrier matrix is melted liquid flavour is mixed in to it and the resulting viscous material is allowed to feed through the extruder under high pressure. The extruded product is subject to cool immediately resulting in to hard structure. This method is best suitable for the highly sensitive flavours like the citrus oils and has batter shelf life. Extrusion provides the large particle size and excellent protection against oxidation with controlled release properties. Like spray drying there are some problems associated with the extrusion process such as: loss of flavour components as result of structural defects and cracks.  d) Molecular inclusion method As the name suggested this technique involves the entrapment of flavour molecule in to the cavity. This capability is well acquired by cyclodextrin (α,β,γ). The interaction generally occurs with lipophilic molecules. e) Fluidised bed coatings Fluidised bed granulation process (also known as agglomeration) A fluidised bed works by initially fluidising a dry flavouring and then spraying the coating material onto it. Particles in the path of the spray get slightly wet and sticky. These particles interact with the other particles in the bed of material and forms a coating layer over the surface and protect the flavour loss. Fluidised bed processing is well known for the controlled release of the flavour. 21.5 Conclusion Encapsulation and slow release covers the latest developments in flavour stabilisation and successfully applied in the flavour industry. There are various technologies available in the industry but not a unique solution. From the array of encapsulation and emulsification choices to choose from hydrocolloids provides the best, effective, and economical alternative to conventional systems. In addition to improving the quality of food product hydrocolloids guarantee manufacturer simpler and most cost effective option.