Janez Hribar

Synthesis of higher alcohols during cider processing

Ciders from two apple cultivars Gloster and Gala, were prepared. Apples were crushed and juice was extracted, immediately after crushing or after 24 h of maceration. Juice was allowed to ferment at 15°C and analysed for higher alcohols and sugars during fermentation. All higher alcohols analysed increased during fermentation as a result of yeast activity. More higher alcohols were synthesised in cider made from Gala cultivar than in cider from Gloster cultivar. Maceration increased the synthesis of iso-amyl alcohol, 2-phenyl ethanol, n-propanol, n-butanol, iso-butanol and methanol. Sensory evaluation classified cider made from non-macerated Gloster cultivar as the best followed by non-macerated Gala cultivar and macerated Gala cultivar. Sensory evaluation score correlated negatively to the sum of higher alcohols.

Effect of location in the canopy on the colour development of three apple cultivars during growth

BACKGROUND Homogeneity in appearance is one of the quality aspects asked for in the supply chain. Decreasing the biological variation in batches of harvested apples (cultivars Braeburn, Fuji and Gala) becomes increasingly important. Skin colour is one of the aspects that determine both optimal harvest and stage of development. Skin colour is affected by location in the canopy. The rules of development of biological variation are now established and will be used on skin colour data. RESULTS The Minolta colour aspects a*, b* and L* measured before commercial harvest change in a sigmoidal fashion and can be analysed including the biological variation, with a logistic model in indexed nonlinear regression, obtaining explained parts of above 90%. The mechanism of colour change is not affected by state of development or location in the canopy. The location in the canopy affects the intensity of both red and green colouring compounds. The variation in colouration is not affected by the location in the canopy. CONCLUSION The red-coloured apple cultivar (Gala) depends more on the location in the canopy than the less-coloured cultivars (Fuji and Braeburn). The colour development in Fuji apples is considerably slower, with a much larger variation in stage of development. The location in the canopy affects all aspects of biological variation (biological shift factor and asymptotic starting level of colouration) for all three colour aspects L*, a* and b*, but only the mean value, not the standard deviation. The biological shift factors per colour aspects are linearly related. Once induced, variation remains constant during development.

Phenolic content of strawberry spreads during processing and storage.

This study provides a comprehensive and systematic evaluation of phenolics in strawberry spreads processed according to different industrial procedures and stored under several storage conditions for up to 19 weeks. Total phenolics were determined spectrophotometrically, and individual phenolics were determined by combined liquid chromatography and mass spectrometry: six anthocyanins, four phenolic acids, two flavonols, one flavanol, and one flavone. During storage, the phenolics were modified. The total anthocyanins, vanillic acid, kaempferol, and luteolin decreased, while salicylic and gallic acids increased. Total phenolics, cyanidin 3-(6″-succinyl-glucoside) (here observed for the first time), protocatechuic acid, quercetin, and catechin remained stable. The best phenolic retention was observed in spreads stored at 4 °C. Therefore, the proposed storage process (use of a cold chain) indicates good retention of phenolics in strawberry spreads, which maintain high nutritional and sensorial quality.

LC–MS analysis of phenolic compounds and antioxidant activity of buckwheat at different stages of malting

The impact of malting on the profile of the phenolic compounds and the antioxidant properties of two buckwheat varieties was investigated. The highest relative increases in phenolic compounds were observed for isoorientin, orientin, and isovitexin, which are consequently major inducible phenolic compounds during malting. Only a minor relative increase was observed for the most abundant phenolic compound, rutin. The radical-scavenging activity of buckwheat seeds was evaluated using ABTS and DPPH assays. A considerable increase in total phenolic compounds and higher antioxidant activity were observed after 64h of germination, whereas kilning resulted in decreased total phenolic compounds and antioxidant activity. Higher antioxidant activities for extracts were found for buffered solvents than for pure methanol and water. Changes in the composition of the phenolic compounds and increased antioxidant content were confirmed by several methods, indicating that buckwheat malt can be used as a food rich in antioxidants.

Influence Of Trehalose Addition On Instrumental Textural Properties Of Strawberry Pastes

Objective of this study was investigation of influence of trehalose addition (3, 5 and 10%) on instrumental textural properties of evaporated and freeze-dried strawberry pastes. As a control, strawberry paste without addition of trehalose was used. Addition of trehalose had influence on both, hardness and stickiness of the samples, but it is very important to define the amount of trehalose in order to achieve desirable properties. With addition of trehalose hardness of both, evaporated and freeze-dried samples decreased, from 29.89 N to 14.72 N for evaporated samples and from 184.83 N to 44.95 N in freeze-dried samples. Also, from those results it could be seen that freeze-dried samples were much harder than evaporated ones, regardless of trehalose addition. While hardness of samples decreased with addition of trehalose, stickiness increased. Stickiness values were from 0.016 N to 0.0102 N for evaporated samples, and from 0.066 N to 0.018 N for freeze-dried samples. Since evaporated samples had lower values for stickiness they were stickier than freeze-dried ones.

Nutritional, antioxidative, and antimicrobial analysis of the Mediterranean hackberry (Celtis australis L.)

Abstract Celtis australis is a deciduous tree commonly known as Mediterranean hackberry or the European nettle tree. The fruit of hackberry are seldom used for nutritional purposes. The nutritional and physicochemical properties of ripe hackberry fruit from Istria (Marasi village near Vrsar, Croatia) were determined, including water, total fiber, protein, vitamin, mineral, and phenolic contents. This analysis demonstrates that the hackberry fruit is a valuable source of dietary fiber, protein, and vitamins, and of pigments such as lutein, β‐carotene, zeaxanthin, and tocopherols. The seasonal differences associated with the different growth stages for the element composition, total phenolic content, and phenolic profile were also determined for hackberry mesocarp and leaves. Water and ethanol extracts were prepared from mesocarp and leaves harvested at different growth stages and their phenolic profiles and antioxidant and antimicrobial activities were investigated. This study demonstrates that water and ethanol extracts of hackberry fruit and leaves collected at different growth stages contain epicatechin, gallic acid, vanillic acid, 3,4‐dihydroxybenzaldehyde, delphinidin‐3,5‐di‐O‐glucoside, cyanidin‐3,5‐di‐O‐glucoside, and pelargonidin‐3,5‐di‐O‐glucoside. They also show some antimicrobial and antifungal activities. Further studies are needed to identify and define the active ingredients of these hackberry leaf ethanol extracts.

Volatile compounds in Prošek dessert wines produced from white and red grapes.

Budic-Leto I., Humar I., Zdunic G., Hribar J., Zlatic E. (2015): Volatile compounds in Prosek dessert wines produced from white and red grapes. Czech J. Food Sci., 33: 354–360. Prosek dessert wines produced from dried grapes of two native Croatian varieties, one white and one red, had complex volatile compositions. Various categories of volatile compounds were identified using headspace solid-phase micro extraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Sixty-one individual volatile compounds of Prosek were identified. Of these, nine compounds comprised over 95% of the total peak area of volatile aromas detected in Prosek: five esters and four alcohols. The remaining volatile compounds consisted of 11 alcohols, 11 esters, 10 terpenes, 8 aldehydes, 10 ketones, 4 acids, 1 lactone, and 1 norisoprenoide. Only 13 of the 61 aroma compounds showed significant differences between the varieties investigated. These results suggest that the charac teristic aroma of Prosek is very complex and determined predominantly by the unique process of the grape drying.

Influence of Cultivar and Storage Time on the Content of Higher Fatty Acids in Apple Cuticle

Influence of Cultivar and Storage Time on the Content of Higher Fatty Acids in Apple Cuticle The main objective was to determine the fatty acid composition on the surface of apple peel and in seeds. 7 apple cultivars were used: Elstar, Fuji, Gloster, Idared, Jonagold, Pink Lady and Golden Delicious. Apple seeds contain from 8.4% to 15% of water and from 17.1% to 28.0% (f.w.) of fat. The fatty acid content in seeds ranged as follows: linoleic (55.9-62.3), oleic (23.9-30.7%), palmitic (7.1-9.3%), stearic (1.6-2.3%), arachidic (1.2-1.6%), linolenic (0.4-0.7%. Linolic acid is prevalent fatty acid on peel as well. Ratio of linolenic acid on peel is up to 30 fold higher than in seeds. Saturated palmitic and stearic fatty acid ratio is considerably higher in peel than in seeds while is the ratio of oleic acid nearly the same as in seeds. During storage of apples the ratio of palmitic and oleic acid increases, while ratio of linoleic acid considerably decreases. Wpływ Odmiany I Długości Okresu Przechowania Na Zawartość Wyższych Kwasów Tłuszczowych W Epidermie Jabłka Celem badań było określenie zawartości kwasów tłuszczowych w skórce i nasionach jabłka. Testy wykonywano na 7 odmianach jabłek: Elstar, Fuji, Gloster, Idared, Jonagold, Pink Lady i Golden Delicious. Nasiona jabłek zawierały od 8,4 do 15% wody i od 17,1 do 28,0% tłuszczów (w świeżej masie). Stwierdzono następujące zawartości poszczególnych kwasów tłuszczowych w nasionach: kwas linolowy (55,9-62,3%), kwas oleinowy (23,9-30,7%), kwas palmitynowy (7,1-9,3%), kwas stearynowy (1,6-2,3%), kwas arachidowy (1,2-1,6%), kwas linolenowy (0,4-0,7%). Kwas linolowy jest dominującym kwasem tłuszczowym również w skórce. Zawartość kwasu linolenowego jest do 30 razy wyższa w skórce niż w nasionach. Zawartość nasyconych kwasów tłuszczowych: palmitynowego i stearynowego, jest znacznie wyższa w skórce niż w nasionach, podczas gdy zawartość kwasu oleinowego jest zbliżona w skórce i nasionach. W czasie przechowywania jabłek, zawartość kwasu palmitynowego i oleinowego wzrasta natomiast kwasu linolowego znacznie obniża się.

Volatile compounds of freeze-dried sour cherry puree affected by the addition of sugars

ABSTRACT The aim of this work was to determine the influence of the addition (5, 10, or 20 g/100 g) of different sugars (sucrose, maltose, or trehalose) prior to freeze-drying on the key volatile compounds of the sour cherry puree. The key volatile compounds of sour cherries were benzaldehyde, benzyl alcohol, and 2-hexenal. The results obtained for the samples with the addition of sugars were compared to the control sample, the sample without sugar addition. The control sample contained 3.92 mg/kg of benzyl alcohol, 856.61 µg/kg of benzaldehyde, and 15.58 µg/kg of 2-hexenal. Benzaldehyde, the compound described as the typical cherry volatile compound, was determined in the highest amount in the sample with the addition of 10 g/100 g of trehalose (937.51 µg/kg). The highest amount of 2-hexenal was determined in samples with the addition of 10 or 20 g/100 g of trehalose (17.45 and 18.96 µg/kg, respectively). All samples with the sugar addition had lower content of the benzyl alcohol than the control sample. Generally, samples with the addition of sucrose had the lowest amount of examined volatile compounds.

Bioactive compounds and macroelements of chicory plants ( Cichorium intybus L.) after hydroponic forcing in different nutrient solutions

The aim of this study was to measure the bioactive compounds and elemental composition in the leaves of different chicory (Cichoruim intybus L.) cultivars after hydroponic forcing. Five chicory cultivars were studied: three red coloured cultivars: ‘Treviso’, ‘Verona’, and ‘Anivip’; one red-spotted cultivar ‘Castelfranco’; and one green cultivar ‘Monivip’. Developing chicory roots were forced in three different nutrient solutions enriched in nitrogen (+N), enriched in potassium (+N/K), or enriched in phosphorus (+N/P/K) to obtain new vegetative apical buds called chicons, or ‘Belgian endive’. Each of the nutrient solutions was used at three concentrations: 1%, 2%, and 3%. Fifty leaf samples (5 cultivars × 10 nutrient solutions) were used for analyses. Total phenolic content, antioxidant potential, and total flavonoid content were determined using spectrophotometric methods at the appropriate wavelengths, and multi-elemental analysis (P, S, Cl, K, Ca, Fe, Zn, Mn, Rb, Br, and Sr) was conducted using energy dispersive X-ray fluorescence spectroscopy. The highest total phenolic and total flavonoid contents of the chicons were observed with the nutrient solution enriched in K, followed by the solution enriched in N, and P. The highest antioxidant potential was observed with the nutrient solution enriched in N. Multi-element analysis detected the major macroelements (> 1 g·kg-1 dry weight) as K, P, Ca, Cl, and S. The nutrient solutions enriched in K and P generally showed the highest contents of these two macroelements in the chicons. Linear discriminant analysis for 19 parameters derived from 43 samples of five cultivars of chicons showed good discrimination between cultivars and nutrient solutions used for hydroponic forcing.