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Abstract

In the present study, six different edible coatings were evaluated to assess their microbicidal efficiency on pre-treated disinfected fresh cut guava. Among all coatings viz. alginate, pectin, carboxy methylcellulose, carrageenan, and starch, chitosan showed significant microbial growth inhibition and preservation of physico-chemical characteristics of fresh cut guava. Further, optimisation of coating parameters i.e. concentration (% w/v) and dipping time (min) was performed using Response Surface Methodology. It revealed that the fresh-cut guava dipped in 1% (w/v) chitosan for 3 min had desirability level of 91% and extension of its shelf life up to 9 days, as compared to 5 days shelf life of uncoated fresh-cut guava, maintaining all its physico-chemical parameters and microbial growth under the permissible level. Validation of optimised conditions was conducted at 5.0 kg scale that resulted in firmness of 1.90 (kg), 2.6 g/100 g sugars content, 8.0 °Brix total soluble solids content, 3.4 pH, 4.1 log CFU g−1 total plate count, 3.1 log CFU g−1 yeast and moulds count, and 3.1 log CFU g−1 total coliforms count on fresh-cut guava at 9th day of refrigeration storage. Shelf life analysis revealed that chitosan coated fresh cut guava can stay fresh till 10th day under refrigeration with maintaining all its nutritive, microbiological, and sensory properties in the acceptable range.

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Acta Alimentaria
Authors:
S. Labidi
,
A. Jánosity
,
A. Yakdhane
,
E. Yakdhane
,
B. Surányi
,
Cs. Mohácsi-Farkas
, and
G. Kiskó

Abstract

Listeria monocytogenes is able to form biofilms on food contact surfaces. Effectiveness of salt concentration, pH, and temperature on the formation of L. monocytogenes biofilms was evaluated individually and in combinations using microtiter plate assay by measuring the optical density. The tested strains differed in their biofilm formation (low, moderate, and strong) ability. At 37 °C, decreasing amounts of biofilms was observed in almost all L. monocytogenes strains when the NaCl concentration increased from 0.05 to 15%, but all strains were able to form biofilm even at 1 °C. There was no significant difference in biofilm formation between pH 4, 5, and 6, except for some strains. When stress conditions were tested in combination, the addition of 15% NaCl significantly inhibited the growth of L. monocytogenes at 1 °C and 4 °C, and the weak biofilm-forming strains were less sensitive to the temperature and to NaCl treatments than the strong biofilm-forming strains. These results enhance our knowledge of the application of NaCl, temperature, and pH stresses in the food industry and provide basis to develop new strategies for control of biofilm formation of this pathogen.

Open access

Abstract

In this study, 25–25 milk samples (25 colostral and 25 mature) collected at different lactational stages were used to analyse the fatty acid composition of breast milk. A gas-chromatographic method was used to perform and analyse the transmethylation of total milk lipid extracts. The milk samples contained 20 different fatty acids. Palmitic acid (C16:0), stearic acid (C18:0), myristic acid (C14:0), oleic acid (C18:1n-9), and linoleic acid (LA, C18:2n-6) were the major components of total lipid, phospholipid (PL), and triacylglycerol (TAG) fractions. Colostrum had a lower percentage of polyunsaturated fatty acids (PUFAs), a higher percentage of saturated fatty acids (SFAs), and a lower level of eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3) in total lipid than mature milk. Triacylglycerol and PL fractions between colostrum and mature milk samples did not differ statistically.

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Abstract

Measurement of phenolics, colour parameters, and volatile compounds in wines were made from two varieties of table grapes (‘Zaoheibao’ and ‘Summer Black’) using five pretreatment methods (cold maceration, freezing grapes, lower maturity, fermenting grape juice without skin, and adding tartaric acid) and a control treatment. The effect of the pretreatment methods on the quality of wines was assessed using oenological parameters analysis and volatile compounds analysis. The results indicated that the freezing grape and cold maceration pretreatments improved the colour and increased the contents of phenolic and volatile compounds compared with the control, and freezing was considered to be the most suitable pretreatment method for ‘Zaoheibao’ wine. With respect to ‘Summer Black’ wines, cold maceration and lower maturity were considered to be suitable. Cold maceration enhanced the contents of phenolic and volatile compounds, while lower maturity increased the contents of volatile compounds and total acid. Our results provide new insights into the use of table grapes to make different styles of wine.

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Az azbesztszálak kimutatására szolgáló vizsgálatok középpontjában a levegőszennyezettségi értékek álltak, de a 21. században felmerült az igény a problémakör kiterjesztésére. Az elmúlt években megjelent nemzetközi tudományos szakirodalmak megcáfolták az évtizedeken át fennálló feltételezést, miszerint az azbeszt csupán a levegőterheltség révén vált ki kockázatot. Vízminőségi és talajminőségi kutatások által teret nyert az azbesztszálak, különösen a krizotilszálak alternatív transzportútjainak vizsgálatát célzó kutatásterület. Annak ellenére, hogy mind a települési, mind pedig a mezőgazdasági vízgazdálkodás potenciálisan érintett a krizotil-azbeszt jelenléte kapcsán, nincs nemzetközi szinten egységes és elfogadott módszer vagy küszöbérték az egyes vízforrások biztonságára vonatkozóan. A kutatások nyilvánvaló korlátja, hogy csekély mennyiségű és minőségű tudás érhető el. Az azbesztszálak megjelenése az egyes vízbázisokban jelentősen megváltoztatja mind a mezőgazdasági, mind a települési vízgazdálkodás környezeti hatásoknak való kitettségéről alkotott eddigi ismereteinket. Az öntözővizzel és a gyűjtött csapadékkal kijuttatott azbesztszálak hatásainak palettája mára túlhaladta a humán- és állategészségügyi hatásokat, immár figyelmet kell fordítani a vegetációs hatásokra is. Annak érdekében, hogy nagyobb betekintést nyerjünk az azbeszttoxicitás növényekre gyakorolt hatásaiba, sokkal több tudományos eredményre van szükség.

Jelen összefoglaló tanulmányban bemutatjuk az azbeszt, különös tekintettel a krizotil azbeszt legfontosabb tulajdonságait, humán-, állat- és növényegészségügyi kockázatait. Rávilágítunk arra, hogy ismereteink rendkívül hiányosak, valamint felhívjuk a figyelmet a települési és mezőgazdasági vízgazdálkodás érintettségének egyes faktoraira, közvetlen és közvetett kockázati tényezőire, valamint arra, hogy ezek miként hatnak az élőlényekre, kiemelt tekintettel a növényekre.

Open access

Abstract

Oxygen plays a crucial role in all stages of wine production. The aim of this study was to quantify dissolved oxygen in filtered wines trained on fine lees during different technological operations such as racking, coarse filtration, stabilisation of thermolabile proteins, and sterile filtration and bottling. The most significant oxygenation of wine occurs during filtration (1.9–3.57 mg L−1) and during bottling (2.99–4.12 mg L−1). At the same time, oxygen affects the phenolic composition, antioxidant activity and sulphur dioxide.

Understanding and being able to use oxygen correctly during wine production can lead to a reduction in the doses of sulphur dioxide used. It has been shown that wines trained on fine lees are more able to withstand oxygen and, therefore, the sulphur dioxide doses can be reduced substantially. The experiment, in which two different winemaking technologies were observed, was carried out on the Welschriesling variety using both stainless steel tanks and oak barrels.

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Abstract

This work explored the impact of mixed flow spray drying on the physical and functional properties of whey powder without any subsequently added drying agent to increase whey utilisation. Spray drying was performed on a pilot scale using a mixed flow spray dryer. The effects of the inlet air temperature (150–210 °C) and feed flow rate (2–7 L h−1) on several responses such as moisture content, yield, dispersibility, bulk density, and outlet air temperature were investigated using response surface methodology. In addition, with the optimised parameters, Carr index, Hausner ratio, solubility, wettability, hygroscopicity, degree of caking, crystallinity, and morphology of the obtained whey powder were determined. The investigation revealed that feed flow rate is the main parameter influencing all responses. The inlet air temperature significantly affected the bulk, tapped density, and outlet air temperature. The optimal inlet air temperature and feed flow rate for the production of whey powder were 182 °C and 3.2 L h−1, respectively. Under these parameters the moisture content, yield, bulk density, hygroscopicity, and degree of caking of the obtained product were 28.6, 1.80%, 0.24 g cm−3, 16.10 g H2O/g powder, and 85.56%, respectively.

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Abstract

Membrane filtration has a promising advantage in the processing of egg products. In this study, liquid egg whites (LEW) were separately concentrated by using reverse osmosis (RO) and ultrafiltration (UF) techniques. The first aim of this research was to determine the effects of the concentration pre-treatments on the physico-chemical quality criteria (pH, relative whipping capacity, foaming stability, water holding capacity-WHC, colour) and the rheological behaviour (viscosity, oscillation) of LEW samples. The second aim of this research was to investigate the impact of the membrane pre-treatment on meringue's functional quality attributes such as meringue batter density and meringue batter colour values (L*, a*, b*). The average dry matter of LEW was increased from 12% to 23% by the concentration pre-treatment process (RO and UF), and water was removed from the LEW. In addition, the batter density of meringue cookie samples was 0.37 ± 0.01 g mL−1 in UF and RO. The differences between the pH and dry matter values of the ultrafiltration and reverse osmosis treated groups were found to be statistically similar, and it was observed that the elastic modulus (G′) increased with the increase in frequency in the rheological measurements. It has been determined that G′ is higher than G″ in all samples. An elastic/solid-like (G′ > G″) structural behaviour was determined while increasing the frequency value. It was determined that the WHC of LEW treated with RO was higher than of the group treated with UF. The results of the study showed that while reducing transportation and storage costs, the water content of >80% of LEW (raw material-the treated liquid egg white) removed by UF and RO applications can be suitable to produce meringue batter cookies (semi-finished product).

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Agrokémia és Talajtan
Authors:
Andrea Balláné Kovács
and
János Kátai
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Abstract

For a long time, olive oil has been considered for formulation of biopharmaceuticals and received a prestigious place in cuisine for its unique organoleptic and nutritional properties. Nevertheless, oxidation of fatty acids in olive oil provides short shelf-life and undesirable organoleptic properties. Thus, microencapsulation of olive oil is a considerable promising approach to maintain its quality and biological activities. The objective of this investigation was to prepare extra virgin olive oil microcapsule by sequential technologies, such as water emulsification of olive oil with wall material (matrix) and freeze drying of emulsion. The effect of wall material composition was examined to prepare microcapsule of extra virgin olive oil. Different ratios of wall materials such as maltodextrin (MD), carboxymethyl cellulose (CMC), and gum arabic (GA) were used. Furthermore, effects of emulsification technologies, such as homogenisation with rotor–stator homogeniser (RSH) and cross-flow membrane emulsification (CFME) were investigated. The stability of emulsion was higher when emulsion was prepared by RSH; however, the droplet mean diameter (D32) was lower in case of RSH compared to CFME. The highest encapsulation efficiency (EE) was found as 68.96 ± 2.6% when CFME was adopted and composition of wall materials was 15 g MD, 15 g GA, and 5 g CMC.

Open access