Georgios Blekas

Effect of rosemary extract, chitosan and α-tocopherol on microbiological parameters and lipid oxidation of fresh pork sausages stored at 4 °C

The effect of rosemary extract, chitosan and α-tocopherol, added individually or in combination, on microbiological parameters and lipid oxidation of fresh pork sausages stored for 20days at 4°C was investigated. Microbiological determinations included the enumeration of Enterobacteriaceae, Pseudomonas spp., total viable count, yeasts and moulds and lactic acid bacteria, while pH values were also determined. Lipid oxidation was evaluated through measurement of primary (peroxide value) and secondary (malondialdehyde concentration) oxidation products. Chitosan addition resulted in significant (P⩽0.05) inhibition of microbial growth, while the lowest microbial counts were obtained in the samples containing both chitosan and rosemary, indicating a possible synergistic effect. Chitosan and its combinations with either α-tocopherol or rosemary, and especially the latter combination, showed also the most intense antioxidative effect (P⩽0.05), at least when compared to α-tocopherol alone or the controls, while use of rosemary extract alone had a comparable (P>0.05) antioxidative effect with chitosan and its combinations. Shelf life of samples containing chitosan was almost doubled compared to the remaining samples. In conclusion, the best antimicrobial and antioxidative effects were obtained from the combination of chitosan with the rosemary extract.

Antioxidative properties of water extracts obtained from herbs of the species Lamiaceae.

Essential oils and extracts of aromatic herbs obtained by organic solvents have been extensively studied for their antioxidant activity in lipid substrates. Very little is known about the possible presence of antioxidants in polar extracts from herbs used in preparation of infusions and decoctions. In this work water extracts of six different herbs of the Lamiaceae family (dittany, lemon balm, mint, sage, sideritis and sweet marjoram) were prepared. The extracts were examined for their effect against lipid oxidation in comparison to a tea water extract. Sweet marjoram, sage and dittany extracts were found to have a remarkable capacity in retarding lipid oxidation. Examination by thin-layer chromatography of the freeze-dried extracts, before and after hydrolysis, showed that the extracts were rich in bound forms of phenolic compounds such as hydroxycinnamic acids and flavonoids. Rosmarinic and caffeic acids were detected in all extracts with the exception of those from mint and sideritis. These results indicate that certain plants used for the preparation of infusions could be further studied like tea as sources of antioxidants.Essential oils and extracts of aromatic herbs obtained by organic solvents have been extensively studied for their antioxidant activity in lipid substrates. Very little is known about the possible presence of antioxidants in polar extracts from herbs used in preparation of infusions and decoctions. In this work water extracts of six different herbs of the Lamiaceae family (dittany, lemon balm, mint, sage, sideritis and sweet marjoram) were prepared. The extracts were examined for their effect against lipid oxidation in comparison to a tea water extract. Sweet marjoram, sage and dittany extracts were found to have a remarkable capacity in retarding lipid oxidation. Examination by thin-layer chromatography of the freeze-dried extracts, before and after hydrolysis, showed that the extracts were rich in bound forms of phenolic compounds such as hydroxycinnamic acids and flavonoids. Rosmarinic and caffeic acids were detected in all extracts with the exception of those from mint and sideritis. These results indicate that certain plants used for the preparation of infusions could be further studied like tea as sources of antioxidants.

Olive Oil Composition

Publisher Summary The composition of olive oil is primarily triacylglycerols (~99%) and secondarily free fatty acids, mono- and diacylglycerols, and an array of lipids such as hydrocarbons, sterols, aliphatic alcohols, tocopherols, and pigments. A plethora of phenolic and volatile compounds are also present. Some of these compounds contribute to the unique character of the oil. Fatty acids present in olive oil are palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and linolenic (C18:3). Myristic (C14:0), heptadecanoic, and eicosanoic acids are found in trace amounts. This chapter discusses some classes of minor constituents that are present only in the crude oil. Filtration reduces the initial levels to a great extent whereas refining results in their removal.

Development of a novel whey beverage by fermentation with kefir granules. Effect of various treatments

The development of a novel whey‐based beverage with acceptable organoleptic properties is reported, where various treatments were studied. Kefir yeast immobilized on delignified cellulosic materials (DCM) or gluten pellets proved to accelerate whey fermentation significantly, with the latter support being not so preferable. Kefir granules seemed to achieve similar fermentation times as DCM. The final pH of the product is suggested to be 4.1 since the profile of the volatile byproducts was higher than other pH values tested. The addition of fructose seemed to be beneficial on the volatile content of the product, although its acceptability as determined by a preference panel was similar to that of the control. Finally, black raisin extract appeared to promote fermentation without any positive effect on the preference of the evaluators.

On the importance of total polar phenols to monitor the stability of Greek virgin olive oil

A large number of virgin olive oil samples obtained from different areas in Greece were analyzed for various quality parameters. The work focuses on the colorimetric determination of total phenols with the Folin-Ciocalteu reagent and its importance in predicting shelf life of virgin olive oil. The results indicate a good correlation of total polar phenol content with the stability of the oil. Colorimetric determination of ortho-diphenol content does not seem to be a better means for predicting virgin olive oil stability. RP-HPLC quantification of hydroxytyrosol and tyrosol in their free form gives poor results in the case of freshly extracted oils. It is concluded that until an easy-to-manage HPLC method will be available, which will quantify accurately both free and bound forms of hydroxytyrosol and other phenolics, the colorimetric method for the determination of total polar phenols remains a good practical means to evaluate the stability of virgin olive oil.

Functional properties of single cell protein produced by kefir microflora

Single cell protein (SCP) was produced by aerobic fermentation of cheese whey by kefir microorganisms. A feed-batch system was developed on a bioreactor of 4 1. The experiments were conducted under controlled pH (5.5) and temperature (30 °C) conditions. The biomass was analyzed for protein, lipids, carbohydrates and ash and its functional properties (emulsification, foaming, gelation) were studied. Single cell protein (53.9% protein) exhibited emulsifying properties similar to those of defatted soy flour, while its Ibaming activity and foam liquid stability were much higher. Finally, texture profile analysis of gels, formed by heating water dispersions of SCP, showed that the structures produced were stronger compared with those of gels made with soy flour.

Polar Phenolic Compounds

Publisher Summary Olive oil polar phenol fraction, known for many years as “polyphenols”, is in fact a complex mixture of compounds with different chemical structures obtained from the oil by extraction with methanol-water. Literature on these compounds has increased exponentially in the last 10 years for various reasons. Phenolic compounds are related to the stability of the oil but also to its biological properties. The latter have received much attention and today many phenolic compounds contained in the oil, mainly hydroxytyrosol and its derivatives, are thoroughly investigated with the aim of establishing a relationship between dietary intakes and the risk of cardiovascular disease or cancer. Ongoing and completed studies in this area associate these phenols with the beneficial role of olive oil in human health. This chapter focuses in detail on some of the alternative sources for olive oil phenols.