Filip Dujmić

Optimization of Ultrasound Assisted Extraction of Functional Ingredients from Stevia Rebaudiana Bertoni Leaves

Abstract The aim of the present study was to reveal an effective extraction procedure for maximization of the yield of steviol glycosides and total phenolic compounds as well as antioxidant activity in stevia extracts. Ultrasound assisted extraction was compared with conventional solvent extraction. The examined solvents were water (100°C/24 h) and 70% ethanol (at 70°C for 30 min). Qualitative and quantitative analyses of steviol glycosides in the extracts obtained were performed using high performance liquid chromatography. Total phenolic compounds, flavonoids, and radical scavenging capacity by 2, 2-azino-di-3-ethylbenzothialozine- sulphonic acid) assay were also determined. The highest content of steviol glycosides, total phenolic compounds, and flavonoids in stevia extracts were obtained when ultrasound assisted extraction was used. The antioxidant activity of the extracts was correlated with the total amount of phenolic compounds. The results indicated that the examined sonication parameters represented as the probe diameter (7 and 22 mm) and treatment time (2, 4, 6, 8, and 10 min) significantly contributed to the yield of steviol glycosides, total phenolic compounds, and flavonoids. The optimum conditions for the maximum yield of steviol glycosides, total phenolic compounds, and flavonoids were as follows: extraction time 10 min, probe diameter 22 mm, and temperature 81.2°C.

Reducing Fat Globules Particle-Size in Goat Milk : Ultrasound and High Hydrostatic Pressures Approach

Innovative and eco-friendly food technologies in practical usage today like Ultrasound (US) and High Hydrostatic Pressures (HHP) are feasible to adequately maintain various food properties while processed, such as texture, sensorial and organoleptic characteristics, and microbiological issues as well. Benchmarked attribute of the mentioned approach lies in the ability of US and HHP to control and withhold both temperature and treatment duration. While temperature could be controlled within room ambient, treatment time is mostly below 30 minutes. US and HHP treatment were performed as separate treatments in order to obtain better homogenization. Goat milk was exposed to ultrasonic propagation up to 100 W of nominal power and high pressures up to 600 MPa. Maximum treatment time was 9 minutes. Ultrasonic homogenization indicates enhanced homogeneity of fat globules while high pressure process parameters have a significant influence on the observed mean particle diameter (fat globules). Improved stability and quality of emulsions (goat milk) was obtained by both applied processes. Statistical analysis indicated the influence of process parameters on fat globule size distribution between 0.3 – 4 µm and variance lower than 0.6.

Antioxidant activity of high-pressure processed tangerine juice

High-pressure processing is technology that has the potential to ensure microbiological safety of low pH fruit juices, while retaining freshness, increasing the stability of juice and retaining of all bioactive compounds. Investigation of HHP parameters on antioxidant activity of bioactive compounds from tangerine juice was conducted. Processing time and pressure parameters were chosen to ensure log5 inactivation of microorganisms. Pressures were 0 (fresh juice), 400, 500 and 600 MPa during 5 and 10 min. Antioxidant capacity (DPPH) and FRAP were measured and statistically analyzed using ANOVA and posthoc tests. Obtained results show that processing at lowest pressure leads to 13, 28 % decrease in antioxidant activity, compared to fresh juices. FRAP values slightly increase at 500 MPa (for 7, 29 %), as well as TOAC. The increase in pressure over 500 MPa did not lead to further changes in FRAP and TOAC values. Processing time had a positive influence, as there is an increase in both measured properties. Pressures over 400 MPa are excessive from an economic standpoint, and not necessary to achieve microbiological safety and juice stability, however, there is evidence that HHP influence on the cellular matrix, which results in the increased diffusion from the cells, which increases the antioxidant activity.

Novel Approach for the Development of Functional Goat Milk-based Beverages Using Medicinal Plant Extracts in Combination with High Intensity Ultrasound Treatment

Regardless of its highly valuable nutritive composition, goats milk is less preferred by consumers due to its specific sensory characteristics that are very often regarded as undesirable. On the other hand, traditional medicinal plants from Lamiaceae family, due to their rich bioactive composition, especially polyphenols, and desirable aroma profile, can be used to enhance and improve bioactive and sensory properties of food. In the present study nutritively valuable beverages were produced by enrichment of goats milk with medicinal plant extracts derived from the Lamiaceae family and stabilized by homogenization with high intensity ultrasound treatment. The impact of plant species (lemon balm, mint, lavender, rosemary and sage) and ultrasound treatment duration (5 or 10 min) on the physicochemical, bioactive and sensory characteristics of enriched beverages was evaluated. The addition of plant extracts to goats milk significantly increased the concentration of bioactive components (rosmarinic acid, hydroxycinnamic acid derivatives and luteolin derivatives), in dependence of the added plant extract. The prolongation of the ultrasound homogenization markedly decreased the fat globule size and thus beneficially affected the product stability. Apart from the achieved bioactive enrichment and stability, the developed beverages exhibited significantly improved sensory properties in comparison to plain goats milk, with the highest overall acceptability determined for samples enriched with mint and rosemary.