25.1.2010
Eva Schrampf
Institut für Analytische Chemie und Lebensmittelchemie, Technisch Universität Graz

OMEGA-3 FATTY ACIDS. CHEMISTRY, OCCURENCE, ANALYSIS AND PHYSIOLOGICAL ASPECTS ON HUMAN HEALTH


The famous study on Eskimos in the late 1977 could clearly show the evidence of a strong correlation between nutrition and the incidence of heart diseases. As the Eskimo’s diet is characterized by seafood associated with a high intake of omega-3 fatty acids (FAs), the publication of these findings opened a broad discussion and pushed the research in the field of human nutrition, aquaculture and stock-breeding, reaching the maximum in the beginning of 2000. The first diseases associated with deficiencies on fatty acids in the late 1920ies could be related to the lack of essential omega-6 FAs (e.g. decreased growth, impaired wound healing, impaired reproduction,…) and more than 50 years later clear evidence of the impact of omega-3 FAs on human health could be demonstrated. In this case the balance of omega-3 to omega-6 fatty acids ratio (n-6/n-3) plays an important role in the formation of different diseases, with the most prominent ones- cardiovascular diseases (CV), immunologic and inflammatory disorders but also certain cancers. In the early evolution of humans their diet’s n6/n3- ratio was close to 1. A typical Western diet nowadays shows values even up to 17:1, whereas the Mediterranean diet reaches optimal ratios which lie between 1:1 and 4:1. Omega-3 fatty acids occur naturally in plants, especially a-linoleic acid, with high amounts in linseeds and perilla oil. The most important fatty acids of the omega-3 family are eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) with their high occurrence in fish, seafood, algae, plankton and marine microorganism. The essentiality of these fatty acids for humans is given by the absence or the very slow conversion rates of specific enzymes (desaturases and elongases) for the transformation of linoleic acid (18:2n-6) and a-linolenic acid (18:3n-3) into long chained unsaturated fatty acids belonging to the omega-3 family. The European Food and Safety Authority (EFSA) recommend a daily intake of DHA and EPA of each 250mg- provided from natural sources (fish products) or a wide range of supplementation products (e.g. dairy products, eggs,...). Statistics show that the Austrian fish-consumption increased from 5 kg per year and per capita in 1995 to 8kg in 2009, with frozen fish products and convenience products being the most appreciated ones.

20.1.2010
Lisa-Maria Zefferer
Institut für Analytische Chemie und Lebensmittelchemie, Technisch Universität Graz

CHANGES OF THE AROMA OF WINE DURING PRODUCTION AND STORAGE

All over the world there are hundreds of grape varieties which belong to the genus Vitis and diversify in their appearance, odor, taste as well as in their balance of the content of alcohol and acid. Important characteristics which are responsible for the formation of the typical bouquet of a certain wine are both its chemical composition and varietal aroma. The individual aromatic personality of wines made from each grape variety is due to the varied combinations and concentrations of various compounds. According to this the chemical composition of wines is influenced by the yeasts applied during fermentation where fusel alcohols as well as esters and various acids are developed. Changes of the chemical composition still occur at the last step of vinification (wineaging and winestorage) where an elevating concentration of acetaldehyde as well as increasing contents of higher alcohols are observed. In respect to this next to the winemaker the right conditions for storage have to be ensured also from the consumer´s side.

19.1.2010
Yuliana Reni SWASTI
Institut für Biochemie, Technische Universität Graz

IN VITRO ANTIOXIDANT ACTIVITY OF BLACK RICE EXTRACT IN LOW-DENSITY LIPOPROTEIN (LDL) HUMAN PLASMA

Black Rice has long been consumed in Japan and China and is considered to be a healthy food because of its antioxidant content that able to prevent oxidative stress. Oxidative modification of low-density lipoprotein (LDL) may play an important role in the development of atherosclerosis. The aim of this research is to examine antioxidant activity of black rice extract variety Melik Java to inhibit LDL oxidation.
Hulled black rice (HB) and partially milled black rice (PMB) were sorted and powdered to pass 30 mesh sieve. Fat content was removed by percolation with hexane. Phenolic and anthocyanins in defatted black rice were extracted using methanol-HCl 1% (10:1) for 24 hour in the absence of light at 40° C. The determination of the phenolic content was carried out by the Folin-Ciocalteu method and the anthocyanins content by the pH differential method. The antioxidant activity was evaluated by radical DPPH methods and the inhibition of oxidation human LDL plasma. Rutin was used as a reference antioxidant.
The results show that the phenolic content in HB and PMB extracts were 556 +/- 10 mg GAE/100g (db) and 535 + 10 mg GAE/ 100g (db) respectively and anthocyanins content were 152 +/- 16 mg/100g (db)m and 149 + 11 mg/100g (db) respectively. The radical DPPH scavenging activity of 100 ppm rutin, 100 ppm HB and 100 ppm PMB were 57.89%, 80.16%, and 77.25% respectively. Inhibition LDL oxidation of 60 ppm rutin, 60 ppm HB and 60 ppm PMB were 48.53%, 52.31% and 48.10% respectively. The results above shows that methanol-HCl 1%-black rice extract has more potential antioxidant activity when compared with rutin.