Drying of Garlic Slices Using Convective Pre-drying and Vacuum-Microwave Finishing Drying: Kinetics, Energy Consumption, and Quality Studies

Garlic slices were dehydrated by convective drying (CD) and by a combined method consisting of convective pre-drying followed by vacuum-microwave finishing drying (CPD-VMFD). Drying of garlic using VMFD led to samples with high values of lightness and slightly lower values of the coordinates a* and b*. The treatment CPD-VMFD significantly decreased the drying time from 630 min for CD to 49 min and contributed to an important energy saving compared with CD (54.4–86.3 %). The total drying time was shorter when vacuum microwaves were introduced earlier and microwave power was higher. The highest temperature (114 °C) was found for samples pre-dried to a moisture content of 60 % and then dried at 360 W while showing the lowest energy consumption (98?±?1 kJ?g^?1). In general, the total antioxidant capacity increased after drying of garlic slices; however, the content of total phenolic compounds showed the opposite trend, and thus other compounds, such as allicin, should be involved in the antioxidant capacity of dried garlic. Garlic slices were CP dried until 30 % of moisture content followed by VMFD at 240 or 360 W showed the best results in terms of energy consumption and antioxidant capacity.     

Influence of polyphenols isolated from <Emphasis Type="Italic">Scutellaria baicalensis</Emphasis> Georgi and <Emphasis Type="Italic">Crataegus oxyacantha</Emphasis> on the oxidative stability of cholesterol in butter stored in various conditions

The aim of the present study was to determine whether the exposure of two types of butter (A1, A2) to different conditions (4 °C and 30 °C in darkness and exposed to light 3600–3900 lx at 50 °C) could be stabilized with natural polyphenols. The polyphenols (500 ppm) added to butter included flavones of skullcap in the form of root powder, 95% pure baicalin and procyanidins from the bark of hawthorn. The rate of cholesterol oxide products (COPs) as well as the storage periods were closely connected with sample storage conditions and the type of butter. Among the polyphenols used, the flavones of skullcap proved to be stronger inhibitors of oxidation process than procyanidins of hawthorn. The storage of samples with the addition of flavones at 50 °C and exposed to light resulted in preserving 50% of cholesterol in both types of butter. The lowest amounts of COPs were formed in samples stored at 4 °C with no light exposure and, under the other conditions, in samples with flavones of skullcap added.     

Evaluation of antioxidant and antimicrobial activity of oregano (Origanum vulgare L.) preparations during storage of low-pressure mechanically separated meat (BAADER meat) from chickens

Food Science and Biotechnology - The goal of this study was to determine the effect of Origanum vulgare L. (oregano) preparations on the storage stability of vacuum-packed low-pressure mechanically...     

Enzymatic biodiesel synthesis – Key factors affecting efficiency of the process

Chemical processes of biodiesel production are energy-consuming and generate undesirable by-products such as soaps and polymeric pigments that retard separation of pure methyl or ethyl esters of fatty acids from glycerol and di- and monoacylglycerols. Enzymatic, lipase-catalyzed biodiesel synthesis has no such drawbacks. Comprehension of the latter process and an appreciable progress in production of robust preparations of lipases may soon result in the replacement of chemical catalysts with enzymes in biodiesel synthesis. Engineering of enzymatic biodiesel synthesis processes requires optimization of such factors as: molar ratio of substrates (triacylglycerols: alcohol), temperature, type of organic solvent (if any) and water activity. All of them are correlated with properties of lipase preparation. This paper reports on the interplay between the crucial parameters of the lipase-catalyzed reactions carried out in non-aqueous systems and the yield of biodiesel synthesis.     

Functional relationships between phytochemicals and drying conditions during the processing of blackcurrant pomace into powders

The effect of convective drying, microwave-vacuum drying and their combination applied to blackcurrant by-product on the quality being measured in terms of the content of phytochemicals in the powders was examined. Convective drying, along with the increase in the temperature, linearly reduced the content of anthocyanins, flavonols and chlorogenic acids. Microwave vacuum drying significantly shortened the drying time, and resulted in higher retention of bioactive compounds at higher temperatures in comparison to convection. No functional relationship was observed between bioactive compounds and the power of magnetrons thus between the processing temperature and the content of individual groups of polyphenols, apart from delphinidin-3-O-rutinoside and delphinidin-3-O-glucoside. During the dehydration of blackcurrant pomace the exponential formation of hydroxymethylfurfural was noticed. The antioxidant capacity decreased along with the increase in drying temperature and in parallel with the decrease in anthocyanins content, thus suggesting that those polyphenols considerably influence the antioxidant potential of final products.     

Betalainic and nutritional profiles of pigment-enriched red beet root (Beta vulgaris L.) dried extracts

Red beet root (Beta vulgaris L.) colourants (betalains) are available either as concentrates produced by evaporating beet juice under vacuum, or as powders made by spray-drying a concentrate. The degradation of the pigments is dependent upon temperature, duration of heat treatment, pH and water activity of a product. Recently, a new proprietary method of large-scale chromatographic purification of red beet root extract has been discovered and developed that allows the production of more concentrated betalain formulations. In order to trace the betalainic compositions of the new products in comparison to the currently in-use spray-, air- and freeze-dried concentrates, a chromatographic study on betalains and their degradation derivatives analysed by LC-DAD-ESI-MS/MS was performed. Additionally, nutritional characterisation of the extracts was accomplished.     

Effect of l-ascorbic acid, sugar, pectin and freeze-thaw treatment on polyphenol content of frozen strawberries

The stability of phenolic compounds of three strawberry cultivars was evaluated for changes during prefreezing treatments, storage and various freezing and thawing conditions. Polyphenol content was determined by HPLC-DAD-FL. The sum of assayed polyphenolic (proanthocyanidin and monomeric flavan-3-ols, anthocyanins, ellagic acid, p-coumaric acid) represented 2858.4 mg/kg in Kent, 2893.1 mg/kg in Elkat, and 2438.0 mg/kg in Senga Sengana. After freezing, 4.5-33.6% of polyphenols were lost; protective effects of prefreezing treatments were seen on anthocyanidins and proanthocyanidins: ascorbic acid was the most effective pretreatment, allowing retention of 3.9-27.5% of anthocyanins, and almost total recovery (3.9-23.9%) when associated with liquid nitrogen freezing. Pectin and sugar only allowed retention of 3.0-25.1% and 5.5-25.4% of the antocyanins, respectively. Thawing of the strawberries in a microwave oven (instead of 20 h at 20 °C) had a further positive effect on retention of anthocyanins, proanthocyanins, (+)-catechin and ellagic acid.