2. Methodology

#### 2.1 Materials

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

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

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 composi-

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

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.

tion, which can support or prevent microorganism growth.

mesophilic aerobic bacteria [4, 6–9].

Technology, Science and Culture - A Global Vision, Volume II

food preservation.

[16, 17].

106

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).

#### 2.2 Alginate bead preparation by extrusion

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

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

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 obtained.

#### 2.3 Diameter of alginate beads with cinnamon essential oil

The beads' average diameter was determined with a vernier caliper using 10 beads each time. The experiment was performed in duplicate.

#### 2.4 Water activity of alginate beads with cinnamon essential oil

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 the sample port. This was closed, and instructions were given to start the measurements. The experiment was run in duplicate, with three replicas each time.

Cinnamaldehyde peak areas obtained by GC–MS were related to cinnamaldehyde concentration in the beads, using a calibration curve. For the construction of the curve, six ethyl acetate solutions with different concentrations of cinnamaldehyde standard were prepared and submitted to GC analysis. The conditions hold in the chromatograph were the same as described for the samples obtained from

disintegrated alginate beads. For each solution injected, a cinnamaldehyde peak area was obtained, and the calibration curve was attained by plotting cinnamaldehyde

The densities of cinnamon essential oil and soybean vegetable oil, at room temperature, were determined using a 10 mL capacity glass pycnometer. This was first weighted empty. Then, the pycnometer was filled with distilled water, cleaned outside with a paper tissue, and weighted again. Finally, the pycnometer was entirely filled with either oil, cleaned outside with a tissue, and weighted. The

<sup>ρ</sup><sup>S</sup> <sup>¼</sup> S gð Þ� E gð Þ

where S is the weight of the pycnometer with either oil, E is the empty pycnometer weight, W is the weight of the pycnometer with water, and ρ<sup>S</sup> and ρ<sup>w</sup>

The obtained alginate beads with essential oil had an average diameter of 1.96 � 0.09 mm, which can facilitate their handling and incorporation in the food

Weight loss over time was monitored in beads stored in both hermetic and perforated fruit packages. The high water activity of the alginate beads with cinnamon essential oil (0.971 � 0.002) contributed to their loss of water in the headspaces of the studied packages, which relative humidity was between 53.5 and 89.5%. For the same container type, storage at 25°C allowed higher weight loss than at 4°C (Figure 1). The literature suggests that at higher temperatures, the release rate of both water and essential oil component, such as cinnamaldehyde, is higher. At higher temperatures, their molecular motion facilitates their diffusion; also, gel expansion increases the mobility of the polymer, which also promotes component

Figure 1 also shows that the effect of temperature in weight loss is smaller in the perforated food packages than in the hermetic one. In the fruit package, due to its perforation, regardless of the temperature, the air volume with which the beads keep contact is higher than it is in beads contained in the hermetic package. Since air saturation and equilibrium are not as easily reached in perforated fruit package as they are in the hermetic package, the mass gradient allows more rapid water and essential oil diffusion from the beads. In the hermetic package, the amount of air is

W gð Þ� E gð Þ � <sup>ρ</sup><sup>w</sup> (1)

concentrations in the solutions against their respective peak areas.

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

2.8 Cinnamon essential oil and soybean vegetable oil density

densities were calculated using Eq. (1):

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

3. Results and discussion

3.1 Alginate bead diameter

package, due to their relatively large size.

diffusion through bead pores [22].

109

3.2 Alginate beads weight loss monitoring

represent, respectively, oil and distilled water density.

## 2.5 Alginate beads weight loss monitoring

### 2.5.1 In hermetic package

Three lidless Petri dishes were filled with approximately 0.5 g of alginate beads with cinnamon essential oil and placed into a 1.7 L plastic hermetic package. This was closed and stored at 25°C and the bead was weight registered overtime. The experiments were also run at 4°C. All experiments were carried out in duplicate. The same procedures were followed for alginate beads with soybean oil.

### 2.5.2 In perforated fruit package

Approximately 0.5 g of alginate beads with cinnamon essential oil were deposited in a Petri dish and placed into a 485 mL perforated fruit package. This was closed and stored at 25°C, and the bead weight was registered overtime. The same set of experiments was also run at 4°C. All experiments were carried out in duplicate, with three replicas each time. The same procedures were repeated for soybean oil beads.

## 2.6 Determination of relative humidity inside hermetic and perforated fruit packages

A fiber hygrometer (Durotherm, Haiterbach, Germany) was placed, without its basal container, inside an empty hermetic or perforated fruit package. The package was closed and stored at 25°C. The relative humidity value displaced by the equipment was registered until it reached a constant value. Once constant, the value was taken as the relative humidity of the environment inside the package. The same experiments were run at 4°C. The measurements were taken in duplicate.

#### 2.7 Cinnamaldehyde release from alginate beads with cinnamon essential oil

Lidless Petri dishes were filled with approximately 0.5 g of cinnamon essential oil alginate beads; three of them were placed into a 1.7 L plastic hermetic package and one in a 485 mL perforated fruit package. The packages were closed and stored at 4°C for 7, 14, or 21 days.

After the storage time, approximately 0.5 g of alginate beads from each condition (hermetic or perforated fruit package) were left overnight in a 40 mL sodium citrate solution (0.055 M) in a closed glass flask and under gentle stirring (578 rpm) with a magnetic stirrer. When the beads were completely disintegrated, 10 mL ethyl acetate was added to recover the essential oil released from the beads. Stirring with a magnetic stirrer was maintained at 578 rpm for 15 min. The ethyl acetate phase was recovered, and its cinnamaldehyde concentration was quantified using an Agilent 6850 N gas chromatograph (GC) (Agilent Technologies, Saint Catherine, California, USA) coupled to an Agilent 5975 C mass detector (MS) (Agilent Technologies, Sta. Clara, CA), as described by Aguilar-González et al. [3]. The GC unit contained an Agilent HP-5 column (30 cm 0.25 cm, 0.25 μm film thickness) in which helium was used as carrier gas at a 1.1 mL/min flow. The injector temperature was 250°C, and the oven temperature was held at 300°C, with the following temperature rate: 60°C for 2 min, followed by increasing temperature (10°C/min) until 250°C, being this temperature finally held for 10 min.

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

Cinnamaldehyde peak areas obtained by GC–MS were related to cinnamaldehyde concentration in the beads, using a calibration curve. For the construction of the curve, six ethyl acetate solutions with different concentrations of cinnamaldehyde standard were prepared and submitted to GC analysis. The conditions hold in the chromatograph were the same as described for the samples obtained from disintegrated alginate beads. For each solution injected, a cinnamaldehyde peak area was obtained, and the calibration curve was attained by plotting cinnamaldehyde concentrations in the solutions against their respective peak areas.

### 2.8 Cinnamon essential oil and soybean vegetable oil density

The densities of cinnamon essential oil and soybean vegetable oil, at room temperature, were determined using a 10 mL capacity glass pycnometer. This was first weighted empty. Then, the pycnometer was filled with distilled water, cleaned outside with a paper tissue, and weighted again. Finally, the pycnometer was entirely filled with either oil, cleaned outside with a tissue, and weighted. The densities were calculated using Eq. (1):

$$\rho\_{\rm S} = \frac{\rm{S}\left(\rm{g}\right) - \rm{E}\left(\rm{g}\right)}{\rm{W}\left(\rm{g}\right) - \rm{E}\left(\rm{g}\right)} \times \rho\_{\rm{w}} \tag{1}$$

where S is the weight of the pycnometer with either oil, E is the empty pycnometer weight, W is the weight of the pycnometer with water, and ρ<sup>S</sup> and ρ<sup>w</sup> represent, respectively, oil and distilled water density.

#### 3. Results and discussion

the sample port. This was closed, and instructions were given to start the measure-

Three lidless Petri dishes were filled with approximately 0.5 g of alginate beads with cinnamon essential oil and placed into a 1.7 L plastic hermetic package. This was closed and stored at 25°C and the bead was weight registered overtime. The experiments were also run at 4°C. All experiments were carried out in duplicate.

Approximately 0.5 g of alginate beads with cinnamon essential oil were deposited in a Petri dish and placed into a 485 mL perforated fruit package. This was closed and stored at 25°C, and the bead weight was registered overtime. The same set of experiments was also run at 4°C. All experiments were carried out in duplicate, with three replicas each time. The same procedures were repeated for soybean

2.6 Determination of relative humidity inside hermetic and perforated fruit

2.7 Cinnamaldehyde release from alginate beads with cinnamon essential oil

Lidless Petri dishes were filled with approximately 0.5 g of cinnamon essential oil alginate beads; three of them were placed into a 1.7 L plastic hermetic package and one in a 485 mL perforated fruit package. The packages were closed and stored

After the storage time, approximately 0.5 g of alginate beads from each condition (hermetic or perforated fruit package) were left overnight in a 40 mL sodium citrate solution (0.055 M) in a closed glass flask and under gentle stirring (578 rpm) with a magnetic stirrer. When the beads were completely disintegrated, 10 mL ethyl acetate was added to recover the essential oil released from the beads. Stirring with a magnetic stirrer was maintained at 578 rpm for 15 min. The ethyl acetate phase was recovered, and its cinnamaldehyde concentration was quantified using an Agilent 6850 N gas chromatograph (GC) (Agilent Technologies, Saint Catherine, California, USA) coupled to an Agilent 5975 C mass detector (MS) (Agilent Technologies, Sta. Clara, CA), as described by Aguilar-González et al. [3]. The GC unit contained an Agilent HP-5 column (30 cm 0.25 cm, 0.25 μm film thickness) in which helium was used as carrier gas at a 1.1 mL/min flow. The injector temperature was 250°C, and the oven temperature was held at 300°C, with the following temperature rate: 60°C for 2 min, followed by increasing temperature (10°C/min) until

A fiber hygrometer (Durotherm, Haiterbach, Germany) was placed, without its basal container, inside an empty hermetic or perforated fruit package. The package was closed and stored at 25°C. The relative humidity value displaced by the equipment was registered until it reached a constant value. Once constant, the value was taken as the relative humidity of the environment inside the package. The same experiments were run at 4°C. The measurements were taken in duplicate.

ments. The experiment was run in duplicate, with three replicas each time.

The same procedures were followed for alginate beads with soybean oil.

2.5 Alginate beads weight loss monitoring

Technology, Science and Culture - A Global Vision, Volume II

2.5.1 In hermetic package

2.5.2 In perforated fruit package

oil beads.

packages

at 4°C for 7, 14, or 21 days.

108

250°C, being this temperature finally held for 10 min.

#### 3.1 Alginate bead diameter

The obtained alginate beads with essential oil had an average diameter of 1.96 � 0.09 mm, which can facilitate their handling and incorporation in the food package, due to their relatively large size.

#### 3.2 Alginate beads weight loss monitoring

Weight loss over time was monitored in beads stored in both hermetic and perforated fruit packages. The high water activity of the alginate beads with cinnamon essential oil (0.971 � 0.002) contributed to their loss of water in the headspaces of the studied packages, which relative humidity was between 53.5 and 89.5%. For the same container type, storage at 25°C allowed higher weight loss than at 4°C (Figure 1). The literature suggests that at higher temperatures, the release rate of both water and essential oil component, such as cinnamaldehyde, is higher. At higher temperatures, their molecular motion facilitates their diffusion; also, gel expansion increases the mobility of the polymer, which also promotes component diffusion through bead pores [22].

Figure 1 also shows that the effect of temperature in weight loss is smaller in the perforated food packages than in the hermetic one. In the fruit package, due to its perforation, regardless of the temperature, the air volume with which the beads keep contact is higher than it is in beads contained in the hermetic package. Since air saturation and equilibrium are not as easily reached in perforated fruit package as they are in the hermetic package, the mass gradient allows more rapid water and essential oil diffusion from the beads. In the hermetic package, the amount of air is

Figure 1.

Cinnamon essential oil bead weight variation over time. The values are percentages of the initial bead weight.

not easily renewed, and so in this case temperature effect on weight lost from beads is more pronounced.

essential oil release. In point of fact, water release from the two kinds of beads could be different due to the different compositions of the beads, which might entrap water differently. On the other hand, the difficulty to maintain relative humidity stable inside the packages during measurements could threaten the accuracy of the

Percentage of initial cinnamaldehyde present in bead lost after 7, 14, and 21 days of incubation at 4°C.

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

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

As for temperature and humidity effect, the results are not clear enough to draw

Figure 3 provides a more accurate determination of the essential oil loss at 4°C. This temperature was chosen for the trial since a considerable fraction of minimally processed or ready-to-eat food is kept at this temperature before consumption. Essential oil loss is faster in perforated fruit package than in hermetic one. While after 7 days of storage, beads in the perforated fruit package lost 74% of its initial cinnamaldehyde concentration, the ones in the hermetic package lost 43%. In the first case, the diffusion increases sharply until 14 days and then maintains, while in the second case there is a sharp increase, followed by a slow increase, and then

Finally, the results for essential oil loss at 4°C, presented in Figure 3, agree with the results for weight loss at the same temperature exhibited in Figure 1, since both

The density of the cinnamon essential oil used in this study was slightly higher than water density, presenting a value of 1.02 g/L. This value is not in accordance with the literature which normally reports essential oil densities lower than water's [23]. Soybean essential oil density was 0.92 g/L, which was lower than water's, as expected, and similar to what was reported in the literature (0.91 g/L) [24].

The study of water release behavior from beads is important to guarantee the best storage condition for the beads and to keep them from losing their appearance qualities. If beads' water loss is considerable, their aspect changed from white shiny beads to yellowish dried beads (data not shown). Therefore, during storage, beads should be kept in considerably high humidity environments where a rapid equilibrium with the atmosphere is achieved if one wants to avoid substantial water loss. The results obtained suggest storage in hermetic environment with limited head-

method.

Figure 3.

a conclusion.

4. Conclusions

111

diffusion tends toward equilibrium.

space air content and low temperature.

cases indicate higher releases in perforated fruit package.

3.4 Cinnamon essential oil and vegetable soybean oil density

Lastly, bead water loss, and consequently the weight loss, is sharper when the relative humidity is the lowest. Figure 1 indicates higher weight loss for the perforated package at 25°C, followed by hermetic package at 25°C, perforated package at 4°C, and hermetic package at 4°C, and the relative humidities in the headspace of these containers were 53.5, 76.0, 86.0, and 89.5%, respectively.

#### 3.3 Bead essential oil loss monitoring

Figure 2 provides a rather empirical way to estimate essential oil release from the bead. The graphs represent the difference between the weight loss from beads with essential oil, where both water and essential oil can be lost to the environment, and the weight loss from beads with soybean oil where, in principle, water is the only element with worth noticing volatility. Therefore, monitoring the weight difference between essential oil beads and vegetable oil beads over time could be a way to estimate the essential oil loss from cinnamon beads. The graphs represent the cumulative difference between weight loss from soybean oil beads and weight lost from essential oil beads, over time.

Figure 2 suggests an increase in essential oil release over time, for the four studied cases. These results, however, should be only indicative of the trend observed for essential oil released and should not be taken as exact values for

Figure 2.

Differences between the percentage of weight loss in soybean oil beads and the percentage of weight loss in essential oil beads. The values are cumulative over time.

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

Figure 3.

not easily renewed, and so in this case temperature effect on weight lost from beads

Cinnamon essential oil bead weight variation over time. The values are percentages of the initial bead weight.

Lastly, bead water loss, and consequently the weight loss, is sharper when the relative humidity is the lowest. Figure 1 indicates higher weight loss for the perforated package at 25°C, followed by hermetic package at 25°C, perforated package at 4°C, and hermetic package at 4°C, and the relative humidities in the headspace of

Figure 2 provides a rather empirical way to estimate essential oil release from the bead. The graphs represent the difference between the weight loss from beads with essential oil, where both water and essential oil can be lost to the environment, and the weight loss from beads with soybean oil where, in principle, water is the only element with worth noticing volatility. Therefore, monitoring the weight difference between essential oil beads and vegetable oil beads over time could be a way to estimate the essential oil loss from cinnamon beads. The graphs represent the cumulative difference between weight loss from soybean oil beads and weight lost

Figure 2 suggests an increase in essential oil release over time, for the four studied cases. These results, however, should be only indicative of the trend observed for essential oil released and should not be taken as exact values for

Differences between the percentage of weight loss in soybean oil beads and the percentage of weight loss in

these containers were 53.5, 76.0, 86.0, and 89.5%, respectively.

Technology, Science and Culture - A Global Vision, Volume II

is more pronounced.

Figure 1.

Figure 2.

110

3.3 Bead essential oil loss monitoring

from essential oil beads, over time.

essential oil beads. The values are cumulative over time.

Percentage of initial cinnamaldehyde present in bead lost after 7, 14, and 21 days of incubation at 4°C.

essential oil release. In point of fact, water release from the two kinds of beads could be different due to the different compositions of the beads, which might entrap water differently. On the other hand, the difficulty to maintain relative humidity stable inside the packages during measurements could threaten the accuracy of the method.

As for temperature and humidity effect, the results are not clear enough to draw a conclusion.

Figure 3 provides a more accurate determination of the essential oil loss at 4°C. This temperature was chosen for the trial since a considerable fraction of minimally processed or ready-to-eat food is kept at this temperature before consumption. Essential oil loss is faster in perforated fruit package than in hermetic one. While after 7 days of storage, beads in the perforated fruit package lost 74% of its initial cinnamaldehyde concentration, the ones in the hermetic package lost 43%. In the first case, the diffusion increases sharply until 14 days and then maintains, while in the second case there is a sharp increase, followed by a slow increase, and then diffusion tends toward equilibrium.

Finally, the results for essential oil loss at 4°C, presented in Figure 3, agree with the results for weight loss at the same temperature exhibited in Figure 1, since both cases indicate higher releases in perforated fruit package.

#### 3.4 Cinnamon essential oil and vegetable soybean oil density

The density of the cinnamon essential oil used in this study was slightly higher than water density, presenting a value of 1.02 g/L. This value is not in accordance with the literature which normally reports essential oil densities lower than water's [23]. Soybean essential oil density was 0.92 g/L, which was lower than water's, as expected, and similar to what was reported in the literature (0.91 g/L) [24].

#### 4. Conclusions

The study of water release behavior from beads is important to guarantee the best storage condition for the beads and to keep them from losing their appearance qualities. If beads' water loss is considerable, their aspect changed from white shiny beads to yellowish dried beads (data not shown). Therefore, during storage, beads should be kept in considerably high humidity environments where a rapid equilibrium with the atmosphere is achieved if one wants to avoid substantial water loss. The results obtained suggest storage in hermetic environment with limited headspace air content and low temperature.

Temperature was the most determining parameter in weight loss (this was higher at 25°C), followed by the type of package used (weight loss was faster in perforated fruit package).

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At refrigeration temperature, the essential oil release rate was higher in perforated fruit package than in the hermetic package, which is expected due to the higher mass gradient in the first case.

Additional studies are needed to evaluate the temperature effects on essential oil release. This is helpful to assure the minimum essential oil loss during storage and to understand the essential oil release profile in a chosen package system for fresh food products.
