Co-microencapsulation of Lactobacillus rhamnosus and krill oil by spray-drying
Graphical abstract
Introduction
Currently, obesity has become a global problem that is related to an increased risk of various types of chronic degenerative diseases, and studies on the role of diet as an environmental factor that can lead to obesity have increased (Han et al., 2018; Lee et al., 2015). Therefore, the development of functional foods has gained interest in the scientific community. Probiotic bacteria and omega-3 fatty acids are perhaps the best characterized and widely studied examples of functional ingredients.
Probiotics provide relevant health benefits, such as the inhibition of pathogenic microorganisms, prevention and treatment of intestinal diseases, the reduction of lactose intolerance, prevention and treatment of allergies and have anticancer/antimutagenic activities. These benefits are influenced by the ability of probiotic microorganisms to survive in the food product and to multiply within the host (Dias et al., 2017). Lactobacillus rhamnosus is particularly useful as a probiotic because of its ability to adhere to intestinal cells, colonize the intestine and exclude or reduce pathogen adherence as well as its persistence and proliferation. This adherence and colonization capacity is considered a contributing factor for immune modulation, pathogen exclusion and better contact with the mucosa (Capurso, 2019). L. rhamnosus also produces compounds that antagonize the growth of pathogens and helps maintain a normal and balanced bacterial flora. However, the viability of probiotic bacteria is affected by a variety of stressors such as heat, acidic and enzymatic conditions of the gastric tract, as well as storage conditions.
On the other hand, omega-3 fatty acids provide important health benefits and are especially recommended for people suffering from chronic degenerative diseases (Eratte et al., 2015). Krill oil (KO) is one of the richest sources of omega-3 fatty acids. Various animal and human studies have suggested that KO has a variety of biological functions, including improved brain function, reduced cardiovascular diseases, non-alcoholic fatty liver disease, metabolic syndrome, premenstrual syndrome, inflammation, colon cancer and attention deficit hyperactivity disorder among others (Zhu et al., 2015; Vigerust et al., 2013). Furthermore, between 30 and 65% of the fatty acids in KO are incorporated into phospholipids (PL), unlike the fatty acids in fish, which are stored mainly as triacylglycerides (TAG). Some studies have found that the special structure of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) esterified as PL in KO provide greater cardioprotective effects than EPA and DHA bound to TAG (Liu et al., 2014; Xie et al., 2017). Moreover, KO also possesses astaxanthin which is a powerful antioxidant. Therefore, KO has a great potential to exhibit multi-faceted health benefits with additive or synergistic effects in humans (Shi et al., 2018). However, KO like all oils rich in omega-3 fatty acids are highly susceptible to oxidation during storage, which leads to rancidity.
Both the vulnerability of probiotics to stressors and the susceptibility of omega-3 fatty acids to oxidation can be overcome by encapsulating these functional ingredients in suitable delivery systems. There are different effective encapsulation techniques to preserve the characteristics of functional ingredients until they reach their site of physiological action. In its encapsulated form, the active ingredient is often better protected during processing against enzymatic, chemical, or physical damage. Microencapsulation by spray drying is a promising alternative in the protection of probiotic cells and ω-3 fatty acids. This is an inexpensive, continuous, and rapid process, in which the final product consists of dust particles that contain the immersed bioactive compounds in the wall material.
The microencapsulation of KO and L. rhamnosus has been studied in separate matrices, but there is not information on the synergistic effects that the co-encapsulation of these functional ingredients as a single entity can provide. Misra et al. (2021) assure that co-microencapsulation of probiotic bacteria and bioactive compounds has convenience and cost advantages over microencapsulation of individual ingredients, and this cost-effective approach has been widely used in the pharmaceutical industry. The first study to develop a single microcapsule capable of delivering omega-3 fatty acids and probiotic bacteria together in one particle was carried out by Eratte et al. (2015), who found an increase in the viability of the probiotic bacterium L. casei when it was co-encapsulated with tuna oil rich in omega-3 in complex coacervates. Subsequently, Vaziri et al., (2019) developed co-microcapsules containing L. plantarum and oil rich in DHA and added them to orange juice, which was stored for 4 weeks at 4 ° C and room temperature, the authors reported synergistic interactions that improved the survival capacity of probiotic bacteria and the oxidative stability of DHA.
The use of L. rhamnosus and KO together in the formulation of co-microcapsules obtained by spray drying could be very good due to the possible synergistic interactions and the benefits that these two functional ingredients provide to consumer's health. Additionally, a careful selection of the wall material makes it possible to release the encapsulated component in a controlled and even targeted way during food processing or in the gastrointestinal tract (Joye et al., 2015). Furthermore, the use of proteins as wall materials in the microencapsulation of bioactive compounds has great potential because of their nutritional value and excellent functional properties. The most used proteins for encapsulating food ingredients by spray-drying are whey proteins and gelatin (Gharsallaoui et al., 2007).
This study addresses two major research objectives: (1) Co-microencapsulate different functional ingredients: L. rhamnosus and KO, by means of spray drying of double W1/O/W2 emulsions, characterizing the developed co-microcapsules, and (2) evaluate the survival capacity of probiotic bacteria as a stability parameter during storage of the co-microcapsules at 4 and 35 °C and different relative humidities (10–93%).
Section snippets
Materials, chemicals and reagents
Krill oil (K-REAL) was purchased from Naturaextracta S.A. de C.V. (Guadalajara, México). Lactobacillus rhamnosus lyophilized LC705 (Danisco, Niebüll, Germany) and blue agave inulin (NOBEL FOODS, Jalisco, México) were used in this study as probiotic and prebiotic, respectively. Whey protein (Amfer Foods, México) was used as wall material. Polyricinoleate esters (Grindsted PGPR 90) and acetyl tartaric acid (Panodan SDK) were from Danisco Mexicana, S.A de C.V., México, and employed as emulsifying
Characterization of feeding solutions and emulsions
In this study, solutions of L. rhamnosus and double emulsions (W1/O/W2) of L. rhamnosus and krill oil were prepared, which were fed to the spray drier to obtain microcapsules and co-microcapsules, respectively.
Double emulsions (W1/O/W2) consist of small water droplets trapped inside larger oil droplets that are dispersed in a continuous water phase (Matos et al., 2018).
Through a microscopy study, it was observed that the double emulsion had a spherical morphology with multiple internal drops (
Conclusions
Results showed that co-microcapsules of Lactobacillus rhamnosus/KO exhibit a high content of PL (PC and PE), MUFA and PUFA, which provide them with functional properties that could prevent or delay the appearance of chronic degenerative diseases in humans. Further, its high content of probiotics (11.55 ± 0.23 CFU/g) provides the microcapsules the ability to fight and prevent intestinal diseases, strengthen the immune system, increase the absorption of nutrients, as well as prevent the
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Author statement
Individual contributions to the paper:
Dr. Enrique Bonilla Zavaleta: Conceptualization; Formal analysis.
M.C. Lucero Ivonne Lozano Coavichi: Investigation; Methodology.
M.C. Luz Velasco Rodríguez: Data curation; Supervision.
Dr. Enrique Flores Andrade: Validation; Resources.
Dr. Hugo Sergio García Galindo: Writing - original draft.
Dra. Martha Paola Rascón Díaz: Writing - review & editing.
Declaration of competing interest
The authors confirm that they have no conflicts of interest with respect to the work described in this manuscript.
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