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Research background. Various approaches have been used to present functional lipids including lycopene in a palatable food form to consumers. However, being highly hydrophobic, lycopene is insoluble in aqueous systems and has a limited bioavailability in the body. Lycopene nanodispersion is expected to improve the properties of lycopene, but its stability and bioaccessibility are also affected by emulsifier type and environmental conditions such as pH, ionic strength and temperature. Experimental approach. The influence of soy lecithin, sodium caseinate and soy lecithin/sodium caseinate at 1:1 ratio on the physicochemical properties and stability of lycopene nanodispersion prepared using the emulsification-evaporation methods before and after treatment at different pH, ionic strength and temperature were investigated. The in vitro bioaccessibility of the nanodispersions was also studied. Results and conclusion. Under neutral pH conditions, nanodispersion stabilized with soy lecithin had the highest physical stability and the smallest particle size (78 nm), the lowest polydispersity index (PDI) value (0.180) and highest zeta potential (-64 mV) but the lowest lycopene concentration (1.826 mg/100 mL). Conversely, nanodispersion stabilized with sodium caseinate had the lowest physical stability. Combining the soy lecithin with sodium caseinate at 1:1 ratio resulted in a physically stable lycopene nanodispersion with the highest lycopene concentration (2.656 mg/100 mL). The lycopene nanodispersion produced by soy lecithin also had high physical stability under different pH range (pH=2-8) where the particle size, PDI and zeta potential remained fairly consistent. The nanodispersion containing sodium caseinate was unstable and droplet aggregation occurred when the pH was reduced close to the isoelectric point of sodium caseinate (pH=4-5). The particle size and PDI value of nanodispersion stabilized with soy lecithin and sodium caseinate mixture increased sharply when the NaCl concentration increased above 100 mM, while the soy lecithin and sodium caseinate counterparts were more stable. All of the nanodispersions showed good stability with respect to temperature changes (30–100 °C) except for the one stabilized by sodium caseinate, which exhibited an increased particle size when heated to above 60 °C. The combination of soy lecithin and sodium caseinate was found to increase the bioaccessibility of the lycopene nanodispersion. The physicochemical properties, stability and extent of the lycopene nanodispersion digestion highly depend on the emulsifier type. Novelty and scientific contribution. Producing a nanodispersion is considered one of the best ways to overcome the poor water solubility, stability and bioavailability issues of lycopene. Currently, studies related to lycopene-fortified delivery systems, particularly in the form of nanodispersion, are still limited. The information obtained on the physicochemical properties, stability and bioaccessibility of lycopene nanodispersion is useful for the development of an effective delivery system for various functional lipids., Pozadina istraživanja. Različitim se pristupima nastoji potrošače opskrbiti funkcionalim lipidima, uključujući likopen, u obliku prikladnom za jelo. Međutim, zbog svoje izuzetne hidrofobnosti likopen nije topljiv u vodenim otopinama i ima ograničenu biološku raspoloživost u organizmu. Pretpostavlja se da bi nanodisperzije likopena mogle poboljšatie njegova svojstva, ali odabir emulgatora i uvjeti okoline, kao što su pH-vrijednost, ionska jakost i temperatura, utječu na njegovu stabilnost i biološku raspoloživost. Eksperimentalni pristup. Ispitan je utjecaj lecitina iz soje, natrijevog kazeinata, te njihove mješavine u omjeru 1:1 na fizikalno-kemijska svojstva i stabilnost nanodisperzija likopena dobivenih kombinacijom metoda emulgiranja i uparavanja prije i nakon obrade pri različitim pH-vrijednostima, ionskoj jakosti i temperaturama. Također je ispitana biološka raspoloživost dobivenih nanodisperzija. Rezultati i zaključci. Pri neutralnoj pH-vrijednosti, najbolja stabilnost i najmanja veličina čestica (78 nm) nanodisperzija, te najniži indeks polidisperzije (0,180) i najveći zeta-potencijal (–64 mV), ali i najniža koncentracija likopena (1,826 mg/100 mL) dobiveni su pomoću lecitina iz soje. Nasuprot tome, nanodisperzije stabilizirane pomoću natrijevog kazeinata imale su najmanju fizičku stabilnost. Kombinacijom lecitina iz soje i natrijevog kazeinata u omjeru 1:1 dobivene su fizički stabilne nanodisperzije s najvećom koncentracijom likopena (2,656 mg/100 mL). Nanodisperzije likopena dobivene pomoću lecitina iz soje bile su vrlo stabilne pri različitim pH-vrijednostima (pH=2–8), uz stabilnu veličinu čestica, indeks polidisperzije i zeta-potencijal. Nanodisperzije koje su sadržavale natrijev kazeinat bile su nestabilne, te je pri pH-vrijednosti blizu izoelektrične točke natrijevog kazeinata (pH=4-5) došlo do agregacije kapljica. Veličina čestica i indeks polidisperzije nanodisperzija stabiliziranih pomoću mješavine lecitina iz soje i natrijevog kazeinata naglo su se povećali pri koncentracijama natrijevog klorida većim od 100 mM, dok su one stabilizirane samo lecitinom iz soje ili natrijevim kazeinatom bile stabilnije. Sve su nanodisperzije bile stabilne pri promjenama temperature u rasponu od 30 do 100 °C, osim one stabilizirane pomoću natrijevog kazeinata, kojoj se veličina čestica povećala pri temperaturama iznad 60 °C. Kombinacijom lecitina iz soje i natrijevog kazeinata povećala se biološka raspoloživost nanodisperzija likopena. Fizikalno-kemijska svojstva, stabilnost i probavljivost nanodisperzija likopena u potpunosti su ovisila o tipu emulgatora. Novina i znanstveni doprinos. Proizvodnja nanodisperzija smatra se jednim od najboljih rješenja problema male topljivosti, te loše stabilnosti i biološke raspoloživosti likopena. Trenutno su istraživanja o načinu apsorpcije likopena, osobito u obliku nanodisperzija, još uvijek limitirana. Dobiveni podaci o fizikalno-kemijskim svojstvima, stabilnosti i biološkoj raspoloživosti nanodisperzija likopena korisni su za razvoj učinkovitog sustava opskrbe organizma različitim funkcionalnim lipidima.

Tea leaves (Camellia sinensis) contain bioactive compounds that can help prevent certain diseases. In this study, the inhibitory effect of polyphenolic components of different types of tea leaves (green, oolong and black) extracted using different solvents (ethanol, methanol and water) on α-amylase activity of human saliva were investigated in vitro. Total phenolic content (TPC), total flavonoid content (TFC), ferric reducing/antioxidant power and inhibition of free radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl of the extracts were measured. Content of gallic acid, caffeine and four catechins also were quantified by high performance liquid chromatography. The ethanol extracts had the highest TPC (124.34-231.23 mg gallic acid equivalents (GAE)/g sample), followed by the methanol extracts (124.28-209.76 mg GAE/g sample) and the water extracts (66.89-136.51 mg GAE/g sample). All three solvent extractions of green tea leaves contained the highest TPC, TFC and antioxidant activity, followed by oolong and black tea leaves. Green tea leaves contained higher amounts of catechins than oolong and black tea leaves. All four catechins were detected in green and oolong tea leaves but only gallocatechin gallate was found in black tea leaves. Next, the effect of tea leaves extracts on starch hydrolysis by α-amylase enzyme from human saliva at 37°C was studied. The starches were hydrolyzed with 0.01% enzyme for 240 min and the extent of hydrolysis was determined based on the dextrose equivalent value. The extent of starch hydrolysis by the tea leaves was as follows: green tea > oolong tea > black tea. The low degree of hydrolysis for black tea was due to its strong inhibitory effect on α-amylase activity. Thus, green, oolong and black tea leaves inhibit activity of α-amylase to different degrees due to their differing compositions and structures of phenolic compounds.