Study of Microencapsulated Bioactive Compounds in Food Products

Nowadays, consumers are increasingly aware of diet related health problems and therefore demand natural and safe ingredients as an alternative to synthetic substances, which are commonly used in the food, pharmaceutical and cosmetic industry. This idea is supported by the consumer’s concern about the safety of products containing synthetic chemicals because these synthetic molecules are suspected to cause or promote negative health effects. Recent studies showed that phenolic and carotenoid compounds are important bioactive compounds with human health benefits. However, the development of new functional foods requires technologies for incorporating these ingredients into food in order to use and protect sensitive food components, to ensure protection against nutritional loss, to mask or preserve flavors/aromas and transform liquids into easy to handle solid ingredients. In many cases, microencapsulation can provide the necessary protection for these compounds and among various techniques that can be employed to form microcapsules, spray drying appears to be a well-established and widely used technique. In this contest, propolis, one of the few natural remedies that has maintained its popularity over a long period of time, represents a widely available natural substance very rich in bioactive compounds that have plenty of biological and pharmacological properties, such as immunomodulatory, antitumor, antiinflammatory, antioxidant, antibacterial, antiviral, antifungal, antiparasite activities, among others. Moreover, it is well known that by-products of plant origin represent also an abundant source of sugars, minerals, organic acid, dietary fibre and phenolics which have a wide range of action which includes antitumoral, antiviral, antibacterial, cardio protective and antimutagenic activities for which, however, strategies for their extraction must be developed. With increasing concerns over the use of organic solvents and their disposal, supercritical fluid extraction (SFE), with carbon dioxide (CO2) as solvent and ethanol (EtOH) as co-solvent, is becoming a promising alternative. In particular, due to low cost and high content of value-added products, such as ferulic and pcoumaric acids, brewer’s spent grain, the major by-product of brewing industry, produced in large quantities annually and generally used as feeding stuff, can be used as an attractive adjunct in human nutrition. Moreover, by-products of orange fruits processing industries represent also a promising sources of materials which may be used in the food industry because of their valuable technological and nutritional properties. Hence, the aim of the study was to enhance the antioxidant properties of fish burgers with microencapsulated propolis and extracts from brewer’s spent grain and orange by-products. In particular, spray-drying process was used to microencapsulate propolis (30 g in 100 mL of ethanol 70% v/v) by means of gum Arabic and Capsul in different ratios (1:6 for gum Arabic and Capsul and then 1:20 just for Capsul). Once defined the optimal microencapsulation conditions, an alcohol-free powder able to mask the strong odor of propolis was obtained, thus promoting a potential food application as source of phenolics and antioxidants. Specifically, 5% w/w of spraydried propolis was incorporated in fish burgers. To improve their sensory properties, new ingredients such as potato flakes (3%, 5%, 7% and 10% w/w) and extra virgin olive oil (9% w/w) were tested and optimized to give a final fish product with good acceptability. Proper tests on burgers also demonstrated an effective increase of both phenolic content and antioxidant activity. Then, to extract bioactive compounds from brewer’s spent grain (BSG9 a proper supercritical fluid extraction (SFE) was found. The effects of three factors including pressure (15–35 MPa), temperature (40–60°C) and ethanol concentration (0–60%, v/v) were investigated. Among the extraction variables, the best conditions (35 MPa of pressure, 40°C of temperature and 60% ethanol) were found considering the criterion of maximum concentration of phenolic compounds (0.35 ± 0.01 mg/g BSG), flavonoids (0.22 ± 0.01 mg/g BSG) and antioxidant potential, evaluated by the ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical (2.09 ± 0.04%/g BSG). After, the optimal BSG extract was microencapsulated and finally added to the fish-burger formulation. In particular, microencapsulation was performed by means of a spray-drying, using Capsul as wall material, and modifying inlet temperatures (90-120-150°C) and ratios between extract and carrier (1:2; 1:4; 1:6; 1:8). Lastly, a sensory evaluation on the fish-burgers prepared with the different bioactive powders was carried out in order to establish the best combination of operating parameters. The sample with 5% microencapsulated BSG extract and Capsul solution in ratio equal to 1:2 at 150°C was chosen as the best compromise according to chemical characterization of active powder and sensory evaluation of sample. To finish, the antioxidant properties of fish burger with microencapsulated BSG extract were compared to the control. Results confirmed the potential use of BSG as food ingredient to increase the nutritional quality of fish burgers. Finally, the potential use of orange by-products, traditionally used as molasses for animal feed, fibre (pectin) and for fuel production, as a source of functional compounds and their application in fish burger has been demonstrated. Two SFE and spray drying techniques were comparing; in particular have been used methods found in the literature and techniques identified previously for the BSG, that appeared the best thanks to a final product of good quality with a higher polyphenols, flavonoids and carotenoids content. Then, different percentages of this powder were added to the fish burger until its overall sensory quality reached sensory threshold. 5% of powder represented the highest concentration to be used; in fact fish-burger loaded with this percentage showed both overall quality statistically similar to that of the control sample and an increase of bioactive compound content