1. Introduction

Consumers are increasingly aware of what they eat and demand for more natural food, with less synthetic additives and preservatives. Further, food researchers and producers seek ways to develop effective and stable systems for foodborne pathogen control, based on natural antimicrobials. Among the wide variety of natural antimicrobials explored, essential oils have shown considerable effectiveness in many studied conditions. They are found in plant organs such as flowers, buds, fruits, stem, root, and leaves and are constituted by volatile components that provide them with several properties, including antimicrobial activity [1, 2]. Some essential oils, such as cinnamon, thyme, clove, oregano, and mustard essential oils, have been reported as very effective against mold and bacteria [3–5]. Cinnamon essential oil is mainly composed of cinnamaldehyde (76.34%), which is also the major component responsible for its antimicrobial activity. Other compounds with

antimicrobial activity can be found in the essential oil, namely, caryophyllene, caryophyllene oxide, linalool, and geraniol, among others, and might work synergistically with cinnamaldehyde for cinnamon essential oil antimicrobial effect. Some studies have demonstrated cinnamon essential oil inhibitory effect against food spoilage molds such as Aspergillus flavus, Aspergillus niger, Colletotrichum gloeosporioides, Rhizopus nigricans, and Penicillium expansum, as well as against some mesophilic aerobic bacteria [4, 6–9].

In an aqueous environment, conditions such as temperature and pH affect active compound release [21], while in the vapor phase, temperature and relative humidity might be relevant. The considerable amount of water held within bead structural network also influences encapsulated compound release to the surrounding environment [21], and so it is important to study bead water release and its relation to

Alginate Beads with Essential Oil: Water and Essential Oil Release Behavior

The objective of this study was to evaluate water and essential oil release from alginate beads containing cinnamon essential oil during storage in different pack-

The cinnamon essential oil was obtained from Laboratorios Hersol S.A. de C.V. (Mexico City, Mexico), and soybean oil (Nutrioli®) was bought in a local supermarket. While trans-cinnamaldehyde standard was provided by Sigma-Aldrich (St Louis, USA), sodium alginate was acquired from Sigma-Aldrich (Toluca, México).

For the preparation of alginate beads with essential oil, sodium alginate (3% w/v) was dispersed in distilled water, with constant stirring at 50°C, until obtaining a homogeneous dispersion. Then, Tween 80 (0.2% v/v) was incorporated into the dispersion, followed by cinnamon essential oil (5% v/v). The mixture was emulsi-

The oil in water emulsion obtained was loaded into a 10 mL syringe. This was adapted to a piston pump (Cole-Parmer, USA), and the emulsion was pumped at a 0.1 mL/min flow, into a calcium chloride solution (1 M). After extrusion of 3 g of gel (approximately 30 min), the formed beads were recovered, rinsed with distilled

Beads with soybean oil (Nutrioli®) were prepared using the same procedure described above, substituting the weight of essential oil for the same weight of soybean oil. Since the essential oil was added to the alginate gel in volumetric proportions, cinnamon essential oil and soybean vegetable oil densities had to be determined, to guarantee that the same weight of these components was used in the respective gels, to allow weight loss comparison between the two types of beads

The beads' average diameter was determined with a vernier caliper using 10

A dew point hygrometer (AQUA LAB, 4TEV, Decagon Devices, Inc., USA) was used for alginate beads with cinnamon essential oil water activity determination. Once the equipment was switched on, it was left to equilibrate for 15 min. Subsequently, approximately 1 g of beads was placed in the sample pan and introduced in

fied at 1778 rpm, for 4 min using a high-speed mixer (Silverson L4R).

water, and dried in a laminar flow chamber for 1 hour.

2.3 Diameter of alginate beads with cinnamon essential oil

beads each time. The experiment was performed in duplicate.

2.4 Water activity of alginate beads with cinnamon essential oil

other component release.

2. Methodology

2.1 Materials

obtained.

107

aging conditions and temperatures.

DOI: http://dx.doi.org/10.5772/intechopen.90099

2.2 Alginate bead preparation by extrusion

Due to the essential oil active components' volatility, essential oils can be effective against microbial growth when applied in vapor phase, which is advantageous for food preservation without affecting their sensory attributes. Besides, when applied in the vapor phase, lesser concentrations than direct applications are needed to inhibit microbial growth [10]. Additionally, the use of carrier polymers capable of holding and yet releasing essential oil in the vapor phase has been suggested for food preservation.

Considering the above, it is interesting to contemplate the development of active packaging systems with essential oil for food microbial control in the vapor phase, in which essential oils are incorporated in carriers. Active packages are defined as those that interact with the food they hold to increase the food product shelf life [8]. Antimicrobial active packages containing essential oil can be projected to release volatile essential oil components into the package headspace, which eventually reaches food surface. Once in contact with foodborne microbe on food surface, lag phase can be extended, and complete microbe growth inhibition is possible. The essential oil effect on foodborne microbe will, however, depend on food composition, which can support or prevent microorganism growth.

Some researchers have recently tried essential oil incorporation in films, while others propose their encapsulation in different polymeric matrices. Alginate is a polysaccharide obtained from brown algae widely used for the encapsulation of active compounds due to its biocompatibility, low toxicity, and low cost [11–13]. In food science and technology, it is, indeed, one of the most used polymers for the immobilization of enzymes, organic acids, amino acids, and essential oils [14]. In combination with bivalent (Ca2+ Ba2+, Fe2+, Sr2+) or trivalent (Al3+) cations, it forms soft and thermally stable gels, which is important in the preparation of alginate beads by extrusion [11, 15]. Extrusion is one of the simpler and most used methods to encapsulate active components in alginate beads [11] and consists of dropping alginate hydrogel containing the compounds of interest, with a needle, into a cation solution. Immediate gelation occurs due to the ionic interaction [16]. Some properties of the beads might affect encapsulation efficiency such as bead size, shape, surface morphology, and transfer properties of the polymer. The more spherical the beads, the stronger the beads and the lesser prone to fracture [11]. On the other hand, the physical properties of the hydrogel improve with increasing alginate molecular weight and with increasing cation concentration [12, 14]. Cation solution ionic force, surface tension, and viscosity, as well as needle internal diameter and dropping height, might also affect encapsulation efficiency. Some authors have tried this method for essential oil encapsulation with promising results [16, 17].

The success of an antimicrobial active package with essential oil depends on carrier polarity, permeability, and porosity but also on the volatility and molecular weight of the essential oil volatile components [18, 19]. Carrying material must be permeable and at the same time should have such barrier properties that avoid excessive or undesired loss of active components [20]. For these reasons, migration tests, run under conditions like those used for food storage, provide insights on the migration potential of the active compound in an active package.

Alginate Beads with Essential Oil: Water and Essential Oil Release Behavior DOI: http://dx.doi.org/10.5772/intechopen.90099

In an aqueous environment, conditions such as temperature and pH affect active compound release [21], while in the vapor phase, temperature and relative humidity might be relevant. The considerable amount of water held within bead structural network also influences encapsulated compound release to the surrounding environment [21], and so it is important to study bead water release and its relation to other component release.

The objective of this study was to evaluate water and essential oil release from alginate beads containing cinnamon essential oil during storage in different packaging conditions and temperatures.
