# Cellulose as a Delivery System of Raspberry Juice Volatiles and Their Stability
## 3 Discussion  
Formulation of delivery systems of active ingredients, exemplified in our study by volatile compounds, is of increasing importance for the food industry. Encapsulation systems should be carefully selected, usually due to the high sensitivity of active ingredients. Amorphous carbohydrates have been identified as very effective encapsulation matrices for delivering active ingredients since they can reduce the rate of release of flavor during storage and minimize the rate of oxidation of oxygen-sensitive flavors by environmental oxygen. In both cases the diffusion of guest molecules through the carbohydrate matrix is involved [45]. Retention and stability of volatiles is a complex phenomenon that depends on many factors such as the physicochemical properties of the volatile compounds, as well as type and concentration of the carbohydrate used [15; 20; 21; 22; 46]. Volatiles with high molecular weight have higher retention than low molecular weight volatiles in carbohydrates matrix [47]. [PERSON] et al. [48] showed that retention increased with the molecular weight of the volatile compounds when they studied esters which were spray-dried with gum arabica. It was detected that ethyl hexanoate with higher molecular weight had a higher retention than ethyl butyrate. These results were explained by the greater ability of low molecular weight compounds to diffuse through the matrix during the drying process. Indeed, since these molecules are not linear, molecular weight and molecular size are linked and the latter is the primary factor determining the diffusion of components. When the molecular weight of the volatile increases, its molecular size increases which slows down its diffusion rate [47]. As we observed in our research, not all volatiles of raspberry juice bonded with cellulose during the complexation process, as some of them (such as hexanol, octanol, \(\gamma\)-terpinene, vitispirane, benzyl alcohol, hexanoic acid, trans-caryophyllene, myristicin, myristyl aldehyde and \(\beta\)-cyclocitral) were not detected in cellulose/raspberry complexes. Those volatiles have either low molecular weight or low vapor pressure or a combination of these properties. The same properties were also observed for volatiles that were lost during storage (2-hexenal, lilial, 1-phenyl-ethanoneone). There is a relationship between chemical groups of several classes of flavor compounds and their retention rates. Several studies [26; 49; 50; 46] have showed that alcohols are usually the best retained compounds by carbohydrates because of glycoside linkages with carbohydrate [26]. [PERSON] and [PERSON] [49] studied the retention of volatile compounds (acids, aldehydes and alcohols) in high amylose starch and observed that alcohols had the greatest and aldehydes the lowest retention. A study on the influence of \(\lambda\)-carrageenan on volatile compounds (aldehyde, ketones, ester and alcohol) showed that esters had the highest volatility, followed by aldehydes, ketones and with alcohols as the lowest [50]. Similar results were obtained for the inclusion efficiency of watermelon flavor by \(\gamma\)-cyclodextrintrin which decreased in the order of alcohols \(>\) aldehydes \(>\) esters [46]. When compared to the previous studies about linkage between carbohydrates and chemical groups of volatiles, our results are partially in agreement. As already mentioned, during complexation as well as storage some aldehydes were lost, but also two alcohols from raspberry juice didn't bind to cellulose, thereby showing the importance of chemical structure and the properties of the carrier. The hydrophobicity of volatile compounds is also an important factor that affects retention and release of flavor. Retention of polar (hydrophilic) compounds is expected to be very low. [PERSON] et al. [51] studied the retention of limonene and _trans_-2-hexenal in gum Arabica and propylene glycol alginate solutions by gas chromatography. Limonene, with the higher hydrophobicity, had higher retention than _trans_-2-hexanal which is quite polar.