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Oil Structuring for Improving Healthy and Sustainable Diets: The Case Study of Extra Virgin Olive Oil Oleogelation
Full text linkThe aim of this PhD research project is to develop novel and sustainable strategies to structure liquid oils into pseudoplastic materials, called oleogels, to be used as saturated fat substitutes or as functional components able to modulate lipolysis during human digestion as well as deliver bioactive lipophilic molecules. In this context, the use of extra virgin olive oil (EVOO) as a target oil to be gelled would be particularly interesting due to its well- recognized health-promoting capacity. In this case study, EVOO-based oleogels were developed by using different gelation strategies. The oleogels, after structural characterization, were in vitro digested to study the impact of oil structure on the free fatty acids (FFA) release and polyphenols’ bioaccessibility.
1. Introduction
In accordance with the PhD thesis project previously described (Ciuffarin, 2021), this poster reports the main results of the following activities:
(A1) Study of strategies for oil structuring (e.g., methods and selection of gelators).
(A3) Evaluation of the effect of oleogelation on the gastrointestinal behavior of oleogels by determining the
bioaccessibility of selected bioactive molecules (e.g., polyphenols) as well as the lipolysis degree by using in vitro digestion methodologies.
2. Materials and Methods
Oleogels were obtained by adding 10 % (w/w) of saturated monoglycerides (MG), rice bran waxes (RW), sunflower waxes (SW), and β-sitosterol/γ-oryzanol mixture (PS) in EVOO heated at temperatures higher than the melting temperatures of the different gelators. Additionally, a whey protein-based oleogel (WP) was prepared by mixing EVOO with a WP aerogel prepared following the methodology of Plazzotta et al. (2020). The final oil content in WP-based oleogels was 80% (w/w). Oleogels were characterized for their structure using a texture analyzer (35 mm-diameter cylindrical probe for 5 mm of distance at a crosshead speed of 1.5 mm/s, TA. XT Plus, Stable Micro Systems Ltd, Godalming, UK) and an accelerated release test by centrifuging samples (10000g for 15 min, Mikro 120, Hettich Zentrifugen, Andreas Hettich GmbH and Co, Tuttlingen, Germany).
Unstructured EVOO and oleogels were then subjected to in vitro digestion according to the protocol proposed by Brodkorb et al. (2019). The FFAs released during digestion were assessed by titration (pH-stat). The bioaccessibility of tyrosol (T) and hydroxytyrosol (HT) was evaluated as the percentage ratio between the concentration of these components included in the micellar phase after intestinal in vitro digestion and their concentration in the undigested sample. The polyphenols were determined by HPLC.
3. Results and Discussion
3.1 Oleogel physical properties
Table 1 shows the oil retention capacity and firmness of the considered oleogels. All the samples presented a very high oil retention capacity upon centrifugation (<99%) despite the different firmness. The MG-based oleogel was the weakest gel, followed by WP, RW, SW, and PS. These mechanical properties can be associated with the
different natures of the networks structuring EVOO. In agreement with the literature, MG, RW, and SW formed a crystalline network (da Pieve et al., 2010; Doan et al., 2015), PS generated a fibrillar structure (Scharfe et al., 2019) and protein aerogels absorbed oil in the protein porous structure (Plazzotta et al., 2021).
3.2 In-vitro digestion: FFA release and bioaccessibility
Figure 1 shows the FFA release as a function of the digestion time
of structured into oleogels and unstructured EVOO. The typical
curve of lipid hydrolysis was obtained. The unstructured oil presented FFA release % of about 68%, followed by PS, SW, RW, and MG with 59.1, 50.8, 50.7, and 42.8% respectively. A different behavior was acquired for WP- based oleogels showing the complete digestion of the oil. These results clearly show that the extent of lipid
lipolysis was significantly affected by oil structure. In the case of liposoluble gelators (i.e., MG, RW, SW, PS),
it can be inferred that the lipase activity was hindered by the presence of a structuring network behaving like a
physical barrier to the access of the enzyme to the substrate sites. On the contrary, WP probably
completely dissolved in the gastrointestinal environment thus favouring the emulsification of the oil and thus the lipase activity. In summary, the results demonstrated that the digestibility of the oil can be steered by selecting the proper oleogelator. In the next part of the study, the bioaccessibility of the major EVOO polyphenols (i.e., tyrosol and hydroxytyrosol) was assessed. Despite the higher content of hydroxytyrosol (HT) in EVOO than tyrosol (T) (HT: 248 mg/kg, T: 96 mg/kg), the bioaccessibility of T was significantly higher than that of HT. This result can be explained by considering the different susceptibility to oxidation of the two molecules during digestion (Alberdi-Cedeño et al., 2020). Moreover, differences were recorded among oleogels. Unstructured oil and WP presented the higher T bioaccessibility values, followed by SW, MG and RW, and PS. Since it is impossible to observe a direct effect of gel strength on polyphenol bioaccessibility, it can be speculated a possible interaction between the polyphenols and oleogel network structures. In fact, as well-known, polyphenols are surface-active molecules with the potentiality to interact with other food components.
In conclusion, the results reported in the present study confirm that oleogelation could be a profitable strategy to modulate lipid digestion while delivering bioactive molecules.
4. References
Alberdi-Cedeño, J., Ibargoitia, M. L., & Guillén, M. D. (2020). Study of the in vitro digestion of olive oil enriched or not with antioxidant phenolic compounds. Relationships between bioaccessibility of main components of different oils and their composition. Antioxidants, 9(6).
Brodkorb, A., Egger, L., Alminger, M., Alvito, P., Assunção, R., Ballance, S., Bohn, T., Bourlieu-Lacanal, C., Boutrou, R., Carrière, F., Clemente, A., Corredig, M., Dupont, D., Dufour, C., Edwards, C., Golding, M., Karakaya, S., Kirkhus, B., le Feunteun, S., ... Recio, I. (2019). INFOGEST static in vitro simulation of gastrointestinal food digestion. Nat. Protoc., 14(4), 991–1014.
da Pieve, S., Calligaris, S., Co, E., Nicoli, M. C., & Marangoni, A. G. (2010). Shear Nanostructuring of monoglyceride organogels. Food Biophys., 5(3), 211–217.
Doan, C. D., van de Walle, D., Dewettinck, K., & Patel, A. R. (2015). Evaluating the oil-gelling properties of natural waxes in rice bran oil: Rheological, thermal, and microstructural study. JAOCS,92(6).
Plazzotta, S., Calligaris, S., & Manzocco, L. (2020). Structural characterization of oleogels from whey protein aerogel particles. Int. Food Res. J., 132, 109099.
Plazzotta, S., Jung, I., Schroeter, B., Subrahmanyam, R. P., Smirnova, I., Calligaris, S., Gurikov, P., & Manzocco, L. (2021). Conversion of whey protein aerogel particles into oleogels: Effect of oil type on structural features. Polym. J., 13(23).
Scharfe, M., Ahmane, Y., Seilert, J., Keim, J., & Flöter, E. (2019). On the Effect of Minor Oil Components on β- Sitosterol/γ-oryzanol Oleogels. Eur. J. Lipid Sci. Technol., 121(8)
Secondary Shelf Life: an Underestimated Issue
No full textShelf life and related issues are generally discussed and studied on packed foods. However, when original containers are opened
by consumers or at industrial level, a sharp acceleration of product quality decay suddenly occurs. In these cases, the concept of
secondary shelf life (SSL), that is the period after pack opening during which a food product maintains an acceptable quality
level, should be introduced. SSL and related issues (e.g. food safety, quality, and consumer perception after pack opening) have
received little attention in literature despite the possible remarkable impact on household management of opened products by
consumers as well as on food industry management of raw material and semi-processed foods after opening. In this review, the
SSL issues are critically discussed by focussing on possible spoilage events after pack opening, consumer and food industry
perspectives on SSL, and SSL assessment process
Color Changes of Tomato Purees During Storage at Freezing Temperatures
No full textABSTRACT: The changes in color of unblanched and blanched tomato purees during storage at −7 and −18 °C were studied. They showed the typical sigmoidal-shape of radical reactions and were well described by the Logistic equation (R > 0.95; P < 10−3). After an initial induction time, a progressive increase in the bleaching rate was found for both unblanched and blanched frozen tomato purees. The color changes for the unblanched sample were statistically higher than those for the heated one. In the former case, the bleaching of carotenoids was attributed to both chemical and enzyme-catalyzed oxidation reactions. The effect of storage temperatures on color changes was appreciable only in the case of the unblanched tomato sample
Application of different drying techniques to fresh-cut salad waste to obtain food ingredients rich in antioxidants and with high solvent loading capacity
Full text linkWastes from iceberg salad fresh-cut processing were submitted to air-drying, freeze-drying, and supercritical-CO2-drying with or without ethanol as co-solvent. Drying was combined with grinding to obtain flours. Samples were analysed for macro- and micro-appearance, particle size, dietary fibre, polyphenol content, antioxidant activity, water vapour sorption, water and oil holding capacity. Air-drying produced a collapsed brown material allowing a flour rich in fibre (>260 g/kg) and polyphenols (3.05 mg GAE/gdw) with antioxidant activity (6.04 OD−3/min/gdw) to be obtained. Freeze-drying maintained vegetable structure and colour while partly retaining polyphenols (1.23 mg GAE/gdw). Supercritical-CO2-drying with ethanol as co-solvent, produced an expanded material able to entrap huge amounts of water and oil (43.2 and 35.2 g of water and oil for g of dry sample). Air-dried salad waste derivatives could be used as functional food ingredients, while supercritical-CO2-dried ones can be exploited as bulking agents and absorbers of oil spills or edible oils. © 2017 Elsevier Lt
Modeling the temperature dependence of lipid oxidation rate as affected by the physical state
No full textFeasibility of protein aerogel particles as food ingredient: The case of cocoa spreads
Full text linkThe feasibility of aerogel particles made of whey protein isolate (WP) as food ingredient was studied for the first time. To this aim, cocoa spreads, which traditionally contain large amounts of solid fat, were prepared using sunflower oil as lipid phase instead of fats. Sunflower oil was mixed with sugar, cocoa powder and WP aerogel particles or unstructured WP (control). Two preparation methodologies were applied: (i) mixing ingredients all at once (one-step) and (ii) preliminary oil absorption into aerogel particles, and subsequent mixing with the other ingredients (two-step). WP aerogel spreads showed higher viscosity than control ones, demonstrating the peculiar functionality of porous aerogel particles in entrapping oil. However, the preparation procedure drove the inter-particle interactions among ingredients. In particular, preliminary oil absorption into aerogel particles (two-step procedure) allowed a stronger network to be obtained. Results open to the possibility of applying aerogel particles as food ingredients, highlighting the need for a dedicated process design to maximise the exploitation of their functionality
Structural characterization of oleogels from whey protein aerogel particles
No full textOleogels intended as fat substitutes were prepared by oil dispersion of aerogel particles obtained through freeze-drying (FD) or supercritical-CO2-drying (SCD) of whey protein isolate (WPI) hydrogels (20 g/100 g). SEM revealed that freeze-dried particles presented larger dimensions than supercritical-dried ones. The latter also showed higher oil dispersibility, forming aggregates with lower dimension (300 nm) than those formed by freeze-dried particles (700 nm). Both particles presented oil structuring capability. Freeze-dried particles gave a weak oleogel, while supercritical-dried ones gave a strong (G′ = 3.1 × 105 Pa) and plastic (critical stress = 723.2 Pa) oleogel, with rheological features comparable to those of traditional fats. These results can be explained based on the lower aggregation induced by SCD and on the higher capacity of supercritical-dried particles to form a network in oil through hydrophilic interactions, as suggested by FTIR. Therefore, WPI aerogel particles show the potentiality to be used as food ingredients to prepare oleogels with tailor-made physical properties
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