Evaporation behaviour of DMS in an aqueous solution at infinite dilution – a review

The current article describes the evaporation behaviour of dimethyl sulfide (DMS) in wort. All thermodynamic and technological basics and DMS data are listed. However, the article's target was not just the collection, editing and reviewing of information but also how to predict DMS evaporation behaviour from wort for different temperatures based on the data in the literature. For that particular purpose, a function was first set up that combined all of the information available on evaporation behaviour. In this context, the so‐called activity coefficient (γ_i) is of crucial interest. Owing to the broad basis of literature evaluated, the function set‐up as described can be deemed to be a current and accurate tool for predicting DMS evaporation behaviour, in general, as well as in particular for different boiling systems. Copyright © 2016 The Institute of Brewing & Distilling     

Thermodynamic and activation parameters for the hydrolysis of amylose with Bacillus alpha-amylases in a diluted anionic surfactant solution

The effects of an anionic surfactant, sodium dodecyl sulfate (SDS), on the kinetic behavior in the hydrolysis of amylose with two bacterial alpha-amylases from Bacillus amyloliquefaciens and B. licheniformis were studied. The catalytic rates of both amylases in the present study showed sigmoidal kinetics with increased concentration of added SDS; the rates were increased in the range below the critical micelle concentration (cmc) and then markedly decreased above the cmc. The catalytic rate of the alpha-amylase from B. amyloliquefaciens was more sensitive to the added surfactant than that of the alpha-amylase from B. licheniformis. The diluted SDS at concentrations below the cmc was responsible for the preferential formation of the enzyme-substrate (E-S) complex, and the hydrolytic catalysis of both enzymes was apparently accelerated. Thermodynamic parameters for the E-S complex formation revealed that the apparent enthalpy and entropy changes of both amylases were increased by the addition of the diluted SDS. It is suggested that the increase in hydrolytic rate by the addition of SDS is due to the larger increase in the entropy changes for the E-S complex formation than in the enthalpy changes.     

Membrane fouling during filtration of milk––a microstructural study

The surface morphology and internal microstructure of a membrane are the result of membrane manufacturing processes and subsequent use during fluid processing in industry. Both these structural factors have a great effect on fouling and filtration performance.

In this study, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy were used to comprehensively characterise the surface of unused microfiltration and ultrafiltration membranes, the fouled layer on the surface of membranes used for milk filtration and the internal fouling within the used membranes.

A simple and effective sample preparation method was developed to study the internal membrane structure using high-resolution field emission SEM with low-accelerating voltage. Various methods of structural characterisation were compared and the results showed that for flat sheet membranes AFM is an appropriate and convenient technique for examining the surface topography of membranes. In contrast SEM is a very appropriate technique for examining the cross-sectional and internal structure of a membrane, either unused or fouled.

Using these complimentary techniques it has been shown that internal fouling, during filtration of skim milk, proceeds by protein–polymer and protein–protein interactions. A gel layer forms on the surface of the membrane and has been imaged using SEM. This layer is slightly compressible and densifies as it grows. Fouling initiation commences after a very short filtration time.     

Morphological evidence for uncontrolled proteolytic activity during the ovulatory process in indomethacin-treated rats

The ovulatory process in cyclic rats was studied after prostanoid synthesis was blocked using indomethacin. Animals were injected at 12:00 h in pro-oestrus with 1.0 mg indomethacin or vehicle (olive oil) and killed at 18:30 h in pro-oestrus, at 02:00, 09:00 and 19:00 h in oestrus and at 09:00 h in metoestrus. Additional rats injected with 0.5 or 4.0 mg indomethacin were killed at 09:00 h in oestrus. No differences in either morphology or serum LH concentrations were found between vehicle or indomethacin-treated rats at 18:30 h in pro-oestrus. However, from 02:00 h in oestrus onward, the process of follicle rupture was altered considerably in indomethacin-treated rats, irrespective of the dose. Early vascular changes, observed in control rats at the apex of the follicle, were absent in indomethacin-treated rats. In some follicles, disruption of the theca layers, invasion of the perifollicular tissue by granulosa cells and follicular fluid, and release of the oocyte to the ovarian interstitium were observed at 02:00 h in oestrus. A small number of follicles ruptured at the ovarian surface. Furthermore, invasion of interstitial tissue, rupture of blood vessel walls, production of emboli of granulosa cells and follicular fluid, and inflammatory reactions were observed in oestrus and metoestrus. The results of the present study demonstrate uncontrolled proteolytic activity, and indicate that abnormal follicle rupture (but not inhibition of follicle rupture) is responsible for ovulation failure in indomethacin-treated rats.     

Formation of acid‐precipitated soy protein–dextran conjugates by Maillard reaction in liquid systems

The conjugation reaction between soybean acid‐precipitated protein (SAPP) and dextran in liquid systems via the initial stage of the Maillard reaction was studied. Functional SAPP–dextran conjugates were prepared in 80% ethanol‐reacting system at 50 °C for 6 h, along with 95% ethanol‐reacting system at 60 °C for 24 h. The covalent attachment of dextran to SAPP was confirmed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and gel filtration chromatography.Compared to the classical dry‐heating, the reaction time of glycosylation in the two ethanol systems was largely shortened. Emulsifying activity of SAPP–dextran conjugates obtained by dry‐heating incubation and in ethanol was similar at pH 7.0 and10.0, significantly higher than that of SAPP–dextran mixture or SAPP alone. In addition, SAPP–dextran conjugates obtained in 80% ethanol‐reacting system for 6 h were completely soluble after heating at 90 °C for 20 min. The impact of various processing conditions on the formation of SAPP–dextran conjugates was investigated. This study provides important guidance to create protein–polysaccharide conjugates at mild temperatures in liquid systems.     

Fate of enniatins and beauvericin during the malting and brewing process determined by stable isotope dilution assays

The fate of enniatins A, A1, B, B1 and beauvericin during the malting and brewing process was investigated. Three batches of barley grains were used as starting material, one was naturally contaminated, two were artificially inoculated with Fusarium fungi. Samples were taken from each key step of the malting and brewing procedure, the levels of the toxins were determined with stable isotope dilution assays using liquid chromatography–tandem mass spectrometry detection. Significant increases of the toxins were found during germination of two batches of barley grains, resulting in green malts contamination up to a factor of 3.5 compared to grains before germination. Quantitative PCR analyses of fungal DNA revealed in all batches growth of Fusarium avenaceum during germination. After kilning, only 41–72% of the total amounts of the toxins in green malts remained in kilned malts. In subsequent mashing stage, the toxins in kilned malts predominantly were removed with spent grains. In the final beer, only one batch still contained 74 and 14 μg/kg of enniatin B and B1, respectively. Therefore, the carryover of these enniatins from the initial barley to final beer was less than 0.2% with the main amounts remaining in the spent grains and the malt rootlets.     

Investigation of atmospheric oxidation of propyl gallate in an anionic surfactant system in the absence and presence of ascorbic acid

In this study the applicability of the surface-sensitive Time-of-flight secondary ion mass spectrometry (ToF-SIMS) technique to hair analysis and associated aqueous processing is evaluated. ToF-SIMS analysis of 'as received' human hair indicates the presence of silicones, anionic surfactants, and cationic conditioners, from previous treatments, on the fiber surface. Cleaning of the hair with SLS or SLES results in adsorption of the surfactants onto the fiber surface. In particular, the more non-polar surfactant components have greater substantivity for the fiber surface, as indicated by the relative increase in their ToF-SIMS intensity. Application of the Incroquat Behenyl 18-MEA conditioner to both 'virgin' and bleached hair results in the adsorption of the cationic C18, C20, C22, and C21 surfactant components onto the hair surface. The ToF-SIMS data indicate higher levels of conditioner on the bleached hair relative to the undamaged hair.     

Mechanical properties of the capsules of chitosan–soy globulin polyelectrolyte complex

The mechanical properties of chitosan–soy globulin capsules depend strongly on the pH values of chitosan and soy globulin solutions in the polyelectrolyte complex formation. When a solution of chitosan was dropped into a solution of soy globulin, a thin chitosan-globulin membrane was formed on the surface of the capsules. These capsules were mechanically weaker than the capsules made by complex formation between sodium alginate and chitosan. In this study 5.0 wt% globulin solution and 2.0 wt% chitosan solution were used. The diameter of the capsules obtained was approximately 3 mm. By immersing the capsules into alkaline solution the composite capsule, having a gel core of chitosan, was obtained. Mechanical properties of the capsule were estimated from compressive force–deformation curves derived from large deformation experiments. The mechanical strength of the capsule was found to depend on the pH values of the chitosan and globulin solutions. The capsules prepared from the chitosan solution with pH 5 and the globulin solution with pH 8 showed high mechanical strength. Moreover, reaction time for capsule formation had an effect on the strength of the capsule.     

Influence of process conditions on the separation behaviour of starch–gluten systems

Separation of wheat flour into its constituents starch and gluten was studied using a cone-cone shearing device, with emphasis on the effect of rotation rate, processing time, temperature and water content. This study confirms the two step mechanism previously proposed for the gluten migration: aggregation of gluten protein into gluten domains that subsequently migrate to the apex of the cone. The results show that optimal process conditions for gluten migration are different from the process conditions for gluten aggregation. While gluten agglomeration (step 1) benefits from high temperature, low rotation rate and high water content, gluten migration (step 2) is positively influenced by a high dough viscosity and higher rotation rate.     

A stability study of green tea catechins during the biscuit making process

A green tea extract (GTE) was incorporated into biscuit as a source of tea catechins. The stability of tea catechins in the biscuit making process was studied. A method was developed for the separation and quantification of tea catechins in GTE, dough, and biscuit samples using a RP-HPLC system. GTEs at 150, 200, and 300 mg per 100 g of flour were formulated. The results obtained showed that green tea catechins were relatively stable in dough. The stability of (−)-EGCG and (−)-ECG was determined at an interval of every 2 min during baking. Their stability decreased as the baking progressed and increased as the concentration of GTE was increased in the biscuit dough. The stability of (−)-EGCG also increased as pH of the dough was reduced and made less alkaline.     

Rotary jet head – a device for accelerating the fermentation process in brewing

The world beer market is dominated by lagers, with production estimated at hundreds of millions of hectolitres per year. The vast majority of the beer is produced using CCT (cylindro‐conical tank) technology. Fermentation and maturation are time‐consuming processes and the bottlenecks of beer production. A rotary jet head (RJH) – a device originally used as a cleaning device – is proposed for use as a tool to provide homogeneity in the tank and to increase the activity of the yeast cells by keeping them in suspension during the fermentation process. The main objective of the study was to analyse the impact of mixing the content of the fermentation tank (by the means of an RJH) on the time of fermentation, maturation and cooling. The experiments were carried out under full industrial operational conditions. It was concluded that mechanical mixing, in a CCT of 3800 hL, shortened the time of lager beer production process by ca. 15%, the time of fermentation by ca. 24 h and the cooling time by ca. 35 h. Copyright © 2016 The Institute of Brewing & Distilling     

Effect of cationic charge and hydrophobic index of cellulose‐based polymers on the semipermanent dyestuff process for hair

In this work, the effects of a new class of polymers generally used in hair and skin cleansing products, the SoftCAT (SofCAT SL and SoftCAT SX), on the dye uptake on the hair fibre and the fading effects has been studied. These polymers, based on quaternary ammonium salts of hydroxyethylcellulose, are cationic products that differ in viscosity, hydrophobic substitution index (HS) and/or cationic substitution (CS, % N). UV–Vis spectroscopy has been used to analyse the extracted dyes from the hair cuticle and the cortex. The results indicate that the presence of polymers in the dye bath improve both the quality of the dyeing process and the anti‐fading effect during the washing cycles. This phenomenon is postulated to be attributable to the polymers hydrophobically bonding with the dyes and so facilitating their increased penetration into the hair.     

Changes in aromatic profile of fresh and dried fig – the role of pre‐treatments in drying process

The aromatic profile of volatiles in fresh figs (FF), fresh figs frozen in liquid nitrogen (NF) and dried figs (DF) (dark variety Petrova?a Crna) was characterised by HS–SPME followed by GC–MS. Figs were dried in a pilot plant cabinet dryer using different pre‐treatments to preserve the dried fruit: sulphuring and immersion in a solution of citric acid and ascorbic acid (separately). The adaptability of thin‐layer drying models to whole figs was investigated. Fresh figs and fresh figs frozen in liquid nitrogen differed mainly in the amount of aldehydes. The highest abundance of volatile compounds in dried figs was found in figs pre‐treated with sulphur dioxide and the control, compared to samples immersed in the acid solutions. Preservation was the most successful for the group of terpenes and terpenic compounds, quite good for some esters and ketones, whereas aldehydes were not affected by the used pre‐treatment.     

Mechanical stress distributions in cross‐sections of cucumber cultivars during the fracture process

The fracture process of six cucumber cultivars was examined to explore the mechanical properties that determine cultivar‐specific crispy and crunchy textures. The postfailure portion of the load–strain curves was targeted in cucumber compression tests. The series of fractures after the initial fracture were examined at the tissue level by expressing the two‐dimensional stress intensity as a map. The stress map for the difference between the fracture point and 0.01 s after the fracture point indicated that the stress distribution changed in a broad area for two cultivars (D and F), while it changed locally and in a small area for two other cultivars (A and E). Several load drops were observed on the load–strain curve for the cucumbers. The peak number between the fracture and the local minimal points was quite small for cultivars D and F, whereas it was substantial for cultivars A and E. A global fracture event occurred over the entire cross‐sectional area at the initial fracture for cultivars D and F. The initial fracture occurred locally for cultivars A and E, and there were repeated sequential small local fractures as sample compression progressed. Two other cultivars (B and C), typical of those normally eaten raw, showed intermediate values for most parameters. This measurement provided the first demonstration of structural fracture during a series of load drops. How these postfailure properties will be associated with the texture characteristics of cucumber cultivars is discussed. Copyright © 2005 Society of Chemical Industry     

A laboratory study of surfactant flushing of DNAPL in the presence of macroemulsion

Computed tomography (CT) monitored experiments are conducted in a three-dimensional water-saturated sandpack to evaluate the performance of a biodegradable surfactant (Glucopon-425N) in recovering a residually trapped dense nonaqueous phase liquid (DNAPL) tetrachloroethylene (PCE) from two sandpacks. Effects of flow rate, surfactant concentration, and pore size on the remediation process are evaluated. Axial variation in porosity of a sandpack has significant effect on the residual distribution of DNAPL in the sandpack and its subsequent recovery. DNAPL is recovered in two stages in general: mobilization followed by macroemulsion-solubilization. Mobilized DNAPL is recovered as a free-phase for all the experiments in the 30-mesh sandpack and only limited mobilization was observed in the 50-mesh sandpack. The dominant mechanism of recovery is macroemulsion flow (accounts for 46-86% of solubilized-emulsified PCE) in both the sands which leads to much higher PCE effluent concentration than the solubility limit as determined in batch solubilization studies. The effluent PCE concentration in the later stage depends on surfactant concentration but not on surfactant flow rate or pore size.     

Development of a liquid–liquid extraction method for the determination of pyrimethanil,metalaxyl, dichlofluanid and penconazol during the fermentative process of must by GC‐NPD

BACKGROUND: A rapid, selective and sensitive gas chromatographic method is described for the analysis of four fungicides—pyrimethanil, metalaxyl, penconazol and dichlofluanid, widely used in vineyards—in must and wine, as well as samples during alcoholic fermentation. The effect of alcoholic fermentation on pyrimethanil concentration in synthetic and real musts was studied. RESULTS: The proposed method was based on liquid–liquid extraction followed by gas chromatography with nitrogen–phosphorus detector. n‐Hexane was the most appropriate solvent for extracting the target fungicides in synthetic and real samples. Quality parameters of the proposed method presented good recovery (ca 78.3% for almost all compounds) and precision (between 1.4% and 6.1%), and quantification limits lower than maximum residue limits. However, for dichlofluanid recovery levels of well over 100% were found. CONCLUSIONS: There was no matrix effect in the analysis of pyrimethanil, metalaxyl or penconazol, but this effect was observed for dichlofluanid in synthetic and real matrices. The application of the fermentative process on pyrimethanil fungicide caused a high decrease in the concentration of this compound, and no product appeared in degradation. The decrease of pyrimethanil in fermented samples was similar in both synthetic and real samples. Copyright © 2009 Society of Chemical Industry     

美湿卡烘干过程湿度控制的意义和解决方案

论述了染整烘干过程中湿度控制的意义和原理.介绍了美湿卡烘干过程湿度控制方案,包括布面湿度(回潮率)和排气湿度的在线检测和控制.     

A study of changes in the fat content of some varieties of dry sausage during the curing process

The influence of the curing of dry sausage (chorizo, saucisson, salami) on the chemical composition of lipids was studied in terms of what affects the oxidation and resulting production of volatile aldehydes, mainly hexanal. Microbial fermentation initially increases the unsaturation, although this phenomenon is reversed during the drying-curing process. In this phase the saturation/unsaturation ratio rises in C16 and C18 fatty acids, the increase being higher in chorizo and lower in salami. Stearic acid appears to increase more than palmitic acid, and C16 quotient values show significant differences across a range of commercially-sold brands of each type of sausage. Unsaturation varies in parallel with the iodine value in the three cases studied. Lipolytic phenomena produce fatty acids with a greater amount of linoleic acid than oleic acid. The oxidation of these fatty acids is progressive regardless of whether TBA or carbonyl values are measured. Nevertheless, significant correlations of hexanal concentrations are not evident. The formation of butanal and pentanal (<2 μmol) is very low, and hexanal concentration fluctuates (11-111 μmol) among commercial brands and types of sausage. These concentrations are always much higher in chorizo samples than in those of salami. Statistical multivariant analysis highlights the greater significant differences in salami samples, a sausage which reflects the lack of homogeneity between different industrial processes.     

Application of Kubelka–Munk analysis to the study of translucency in fresh-cut tomato

In order to assess the development of translucency in fresh-cut tomato (Lycopersicum esculentum cv. Belissimo) during refrigerated storage, two experiments were conducted. In the first one, tomato slices obtained from fruits at breaker and at red stage were stored at 5 ± 0.5 °C and monitored at regular intervals for 9 days. In the second one, slices obtained from fruits at the light-red stage were stored at 5 ± 0.5 °C, 9 ± 0.7 °C and 13 ± 0.7 °C for 4 days. Intact (control) fruits were stored at the same conditions and sliced immediately before the evaluations. In both experiments, translucency was assessed using Kubelka–Munk analysis and through visual evaluation using a scale from 0 to 4. The translucency of cut tomato slices increased during storage in both experiments. Fruits at red stage got translucent faster than fruits at breaker stage and the intensity of translucency was also higher for more ripe fruit. The storage temperature did not influence significantly the development of translucency, indicating that the water soaking of the pericarp tissue is not a result of chilling injury. The K/S (absorption coefficient/scattering coefficient) ratio increased during storage for cut fruits and remained practically constant for intact fruits, reflecting the effects of treatment observed visually. Additional experiments indicated that the removal of the locular gel combined or not with washing and drying the slice cut surface inhibited the development of translucency.

Industrial relevance

The development of translucency is a common alteration in the appearance of fresh-cut fleshy tissue after processing, which renders the product unappealing for consumption. It is of interest for the fresh-cut industry to be able to assess the development of translucency and then evaluate the effect of different procedures in its occurrence and intensity. This paper presents the use of Kubelka–Munk analysis, a technique of widespread use in other fields like printing and painting, to assess the development of translucency in sliced tomato and to study how this process is affected by storage temperature and maturity stage of the fruit.