Extraction and encapsulation of Bio-components from Tomato Waste for Food and Biomedical Applications

Tomato waste (TW), the solid residue left after the industrial processing of tomatoes, is considered as one of the most promising candidates to recovery the lycopene. It consists mainly of tomato peels and seeds making up about 3 % to 5 % of the total weight of processed tomatoes which depends on their specific production process. The World Processing Tomato Council (WPTC) estimates that the annual production of tomatoes in Italy is around 5.5 million tons and at a global more than 40 million tons, resulting in the overall production of large quantities of waste after industrial processing of the tomato. Discarding TW directly not only results in a huge loss of valuable materials, but also poses serious management problems from both the economic and environmental point of view. Considering its nutritional properties, however, it is a promising source of biocompounds according to previous studies. Tomato waste consists mainly of pericarp and seeds, of which fiber is the major compound accounting for 25.4 - 50.0 % of the dry matter. The other components are 15.4 - 23.7 % of total protein, 5.4 - 20.5 % of total fat, and 4.4 - 6.8 % of mineral. More importantly, this by-product contains valuable antioxidants which can be extracted by means of proper extraction methods. Effective utilization of food by-products/wastes as a secondary source for new products has been an emerging research topic in recent years. Tomato processing wastes have been the subject of significant research, especially the recovery of lycopene through efficient extraction methods. Unfortunately, lycopene is nonpolar and readily degradable, so lycopene extraction, processing, and analysis must be performed under controlled conditions to minimize oxidative degradation and isomer formation. Conventional methods of lycopene extraction have non-negligible drawbacks such as time-consuming, toxic chemicals and low efficiency. In recent years, a variety of high efficient extraction techniques have emerged, including microwave, ultrasonic, supercritical fluid and pressurized liquid extraction. These non-conventional techniques exhibit several advantages for the extraction of bioactive molecules, such as a shorter processing time, reduction in the use of organic solvents as well as mild operating parameters to avoid thermal degradation. Therefore, they are environmentally friendly and usually result in higher yields and high-quality final extracts. In this thesis, a preliminary characterization of TW was carried out and different extraction techniques (solid-liquid extraction, ultrasound-assisted extraction, microwave-assisted extraction under pressure and solid-liquid multivariable extractor) were investigated with ethanol and water or their mixed solutions as green solvents. One of the objectives of this research project was to recover lycopene from TW using ethanol solutions as green solvents and to improve the extraction rate by modulating process variables. In this study, response surface modeling and kinetic studies were used as tools for processing optimization and the extracts were evaluated as total lycopene yield and antiradical power. Since it is rapidly susceptible to degradation and isomerization upon exposure to heat, light or oxygen, lycopene can lose its activity and medical effects without proper protection. Accordingly, the second research objective of this thesis was to analyze and evaluate the protective effect on lycopene by using different methods (oil-in-water nanoemulsion, spray drying method and supercritical CO2). Among xxx, the oil-in-water nanoemulsion method was carried out with isopropyl myristate as oil phase and Pluronic F-127 as emulsifier. The stability of the nanoemulsion particles and the lycopene content in nanoemulsion were initially characterized at different temperatures. Further, TW extracts as well as oil-in-water nanoemulsions were directly microencapsulated by spray drying and supercritical CO2 using inulin and maltodextrin as wall materials. The encapsulation process was optimized by modulating different parameters (e.g., coating agent composition, inlet temperature, feed flow rate, feed flow rate of CO2 and feed flow rate of N2) and was analyzed using the Response Surface Methodology. The results about the characterization of TW showed on initial moisture content, approximately 84.3 ± 0.83 %. After the drying process, a final moisture of approximately 6 % of residual moisture. Particularly, after the drying process, the TW exhibited a water activity of 0.101 ± 0.042, resulting as suitable for long-term storage in water-proof containers and in the dark for extraction experiments. After crushing, the average diameter of the particles is smaller (732 ± 67 µm), making it possible to directly use TW for extraction. The biomass showed an ash content of 4.1 ± 0.8 %. SLE using hexane as solvent was carried out for the quantification of lycopene as reference. The total lycopene content was 1438.24 ± 44.3 µg/g (dry solid), measured via HPLC. SLE using sunflower seed oil as solvent was carried out for a general traditional extraction. The results showed that the optimal conditions were T = 45 °C, L/S = 20/3 mL/g, stirring speed = 900 rpm, t = 45 min. The total lycopene content was 1237.32 ± 4.80 µg lycopene equivalent/g (dry solid) measured by UV-vis spectrophotometer. UAE extraction using ethanol as solvent as advanced extraction method was carried out. Response Surface Methodology was used to investigate the effect of the ultrasound-assisted extraction parameters on the extract bioactive content. The optimal conditions found by the desirability method (T = 65 °C, t = 20 min, L/S = 72 mL/g, A = 65 %, on/off = 33/30 s/s, V = 90 mL) were experimentally verified and the total lycopene content was 1536 ± 53 µg/g (dry solid), measured via HPLC. It was also found that the frequency of ultrasonic vibration studied (40kHz, 80kHz, 120kHz) did not significantly improve the lycopene extraction yield. SoLVE extraction using ethanol as solvent as the focus of this chapter was carried out. The optimal conditions also found by the desirability method (CCD) (T = 65 °C, t = 41 min, L/S = 27 mL/g, A = 39 %, on/off = 32/30 s/s) were experimentally verified. Under optimal conditions, the trans-lycopene yield was of 546.7 µg/g and the total lycopene yield was 1193.0 µg lycopene equivalents/g. In addition, the extraction kinetic model was found to be consistent with the Peleg’s model through the study of the extraction kinetics during the extraction process. Finally, microwave-assisted subcritical extraction method was used to study and compare the extraction of lycopene with the extraction conditions of UAE and SoLVE. The optimal conditions were T = 100 °C, L/S = 72 mL/g, V = 30 mL, t = 15 min. The maximum total lycopene content was 962.97 ± 42.87 µg/g (dry solid), the trans-lycopene yield was of 662.84 ± 24.55 µg/g (dry solid), measured via HPLC. Due to the instability of lycopene, it is easily degraded under the influence of external factors (temperature, light, oxygen, pH). Therefore, further research on the protection of lycopene is necessary. This study used different technologies to encapsulate and protect lycopene through solid and liquid formulations. In the part of encapsulation, nanoemulsions were found stable for up to three months at the optimal storage temperature (4 °C) as no significant agglomeration was observed. The addition of extracted solution was found to significantly reduce the droplet size and increase the stability of nanoemulsions. The spray drying technology was found efficient for transferring the nanoemulsion to solid powder. The operating conditions at which spray drying reached the highest recovery were the input temperature 170 °C, the gas flow rate 35 m3/h, the flow rate of the nanoemulsion 6 mL/min and the coating agent (maltodextrin) at 40 % w/w. Under the optimal conditions, the recovery of the product reached 80.3 %. Furthermore, as a comparison, a feasibility evaluation of the encapsulation of the obtained extract by spray drying was carried out, investigating the possibility to add inulin in the composition of the wall material. The best results were obtained at the lowest percentage of inulin (21.7 % inulin and 78.3 % of maltodextrins). Finally, a SAA laboratory apparatus was adopted to dry the nanoemulsions, and different coating agents, CO2 flow rate, temperature, feed flow rate, and production recovery were evaluated.