Cation exchange capacity and buffering capacity of neutral-detergent fibres

Dietary fibre buffers the gastrointestinal tract via the inherent buffering capacity of the specific fibre matrix, the quantity of cell wall ingested and the stimulatory effect of cell wall on rumination and/or salivation. The strong bonding of Cu²⁺ ions for carboxy groups permits their use in estimating the cation exchange capacity (CEC) of both pectinaceous materials and pectin-free cell wall fractions. The CEC values observed emphasise the different cation exchange capacities of the various plant cell wall components. Cellulose has a relatively low exchange capacity while lignin and Maillard products have a much greater adsorption. Emphasis is placed on the difficulty in utilising gravimetric determinations to interpret physicochemical effects as well as the diversity of plant sources in terms of gastrointestinal buffering.     

微波加热下美拉德反应条件的优化研究

探讨用均匀设计安排含有定性因素的实验,即将定性因素定量化。运用虚拟变量讨论不同种类的氨基酸、糖、反应液在微波加热下对美拉德反应的影响。结果表明,脯氨酸-葡萄糖-甘油是较好的反应物的选择。     

Iron decreases the antioxidant capacity of red wine under conditions of in vitro digestion

The hypothesis that iron and phenolics interact in the lumen during digestion and, consequently, decrease the antioxidant capacity of phenolics, was investigated in vitro. Mixtures of red wine, iron, and three dietary factors that may reduce or chelate iron in the lumen, namely ascorbic acid, meat and casein, were subjected to a simulated gastrointestinal digestion. The process involved incubation of samples for 4.5 h at 37 °C, at different pHs, in the presence of peptic enzymes and fractionation of digests through a dialysis membrane. Antioxidant capacity (FRAP assay), iron concentration (ferrozine assay) and total phenolic content (Folin-Ciocalteau assay) were measured in the in vitro digests. Iron decreased the antioxidant capacity and the total phenolic concentration of red wine. Ascorbic acid increased, while meat and casein decreased, the antioxidant capacity of red wine. Based on these results, it was concluded that protein and iron interact with red wine phenolics during the in vitro digestion and decrease their antioxidant capacity, supporting the initial hypothesis.     

Quality changes in 12% moisture content canola stored in silo bags under Canadian Prairie conditions

A study was conducted for two storage years (2011–12 and 2013–14) to determine the changes in grain quality while storing 12% moisture content (m.c., wet basis) canola seeds in silo bags under Canadian Prairie conditions. Canola seeds were stored in three silo bags (67 tonnes per bag) and unloaded at three different times (one bag at a time) which represent 20 weeks of storage (unloaded in late winter), 28 weeks of storage (unloaded in spring) and 40 weeks of storage (unloaded after summer storage). Canola seed quality parameters (germination, free fatty acid value (FAV), and moisture content), and intergranular composition (CO₂ and O₂ levels) at different locations in silo bags were analysed every two weeks. Temperature of canola seeds at various locations in the silo bag was recorded every 30 min. The germination of canola seeds at most parts of the silo bags stayed above a safe level up to late winter (20 weeks of storage). At the top layer of the silo bags, germination of canola seeds decreased to below 30% during summer storage (after 40 weeks of storage). Moisture content of canola seeds increased at the top layer in both storage years. The FAV values remained at safe levels until 20 weeks of storage, and increased more than two times the initial values after summer storage. The commercial grades after first, second and third unloading (after 20, 28 and 40 weeks of storage) were Grade 1, Grade 2 and Feed Grade, respectively, in year 1. Whereas for year 2, these were Grade 1, Grade 1 and Grade 2 after first, second and third unloading, respectively. The grain quality analysis and commercial grading results indicated that ambient temperature had a major role in quality of canola during storage.     

Quality and biochemical changes of longan (Dimocarpus longan Lour cv. Daw) fruit under different controlled atmosphere conditions

Sulphur dioxide has been used to control pericarp browning in longan fruit. However, due to health and regulatory concerns, alternative treatments should be tested. The objective of this study was to find the tolerance levels of longan fruit to low O₂ (2%, 5%, 10% and 15%) and elevated CO₂ (5%, 10%, 15% and 20%) at 2 °C. According to the tolerance study, controlled atmospheres (CA) of 5% O₂ + 5% CO₂, 5% O₂ + 10% CO₂ and 5% O₂ + 15% CO₂ were compared with normal air (control) at 2 °C. Pericarp browning and decay incidence of longan were significantly (P ≤ 0.05) higher in control than all the CA treatments. CA storage reduced polyphenol oxidase (PPO) activity, maintained L* value and slowed down a decrease in total phenolic contents (TPC). Pericarp browning was highly correlated with PPO, L* and TPC.     

Structural consequences of dry heating on Beta-Lactoglobulin under controlled pH

Heating in dry state has gained a lot of interest in pharmaceutical and food industries for viral and microbial decontamination of thermo sensible products. Controlled dry heating has now become a common industrial process for improving the functional properties of food proteins. Besides this improvement, chemical modifications in protein structures involving degradation of amino acids, new intra or inter-molecular disulfide bonds, isopeptide bonds, and some other links may occur. These chemical modifications are favored by severe heating under neutral or alkaline conditions, and except disulfide interchanges, are usually not predominant during heat treatments in solution and their occurrence is not well understood. Understanding chemical modifications in protein structure that occur during dry heating of protein powders is a prerequisite for reproducible properties of final products at industrial scale. In the present work, we focused on how dry heating under acidic pH conditions affects the chemical modifications and denaturation/aggregation reactions of whey proteins. Model whey protein (β-lactoglobulin) powders obtained from freeze drying of protein concentrates adjusted to pHs 2.5 & 6.5 were adjusted to a fixed water activity (Aw 0.23). The samples were dry heated at 100 °C for up to 24 hours and structural modifications induced during dry heating were followed. We showed that whatever the pH value, proteins were characterized by irreversible mass losses of 18 Da. Such mass losses were increased at lower pH value. Dry heating mainly generated small aggregates (dimers and oligomers). Strikingly, at pH 2.5 intermolecular disulfide bonds were the only crosslinks between proteins in the aggregated forms while covalent crosslinks other than disulfide bonds also participated at pH 6.5. β-Lactoglobulin hydrolysis was also detected at pH 2.5 and some of the peptides were incorporated in the oligomers. These results underline that chemical modifications in protein structures induced by dry heating are highly pH dependent. Hence, strict control of pH conditions for dry heating is indispensable to give reproducible functionality in products where such modified proteins are incorporated as ingredient.     

Volatile compounds and oxidative stability of Pinus halepensis Mill. seed oil under heating conditions

Heating conditions of Pinus halepensis seed oil were monitored to evaluate the effect of thermo‐oxidation processes on the bioactive compounds contained in the samples. The following parameters were monitored: ultra violet absorption at 232 and 270 nm, fatty acid composition, oxidative stability, antiradical activity and aromatic profiles. Under thermo‐oxidation process, trans fatty acids (TFA) increased and conjugated linoleic acid isomers appeared. The antiradical activity significantly decreased from 73.3% to 52.5% after 120 min of heating. Oxidative stability decreased (r = ?0.70). The volatile profile was heavily influenced by heating with the formation of new volatile compounds, such as the two isomers (E,Z)‐2,4‐decadienal and (E,E)‐2,4‐decadienal. α‐pinene, and the main terpene compound was very vulnerable to heating conditions. Despite its peculiar pleasant aroma and nutritional value, the P. halepensis seed oil should not be used for cooking. Indeed, under frying conditions, its antioxidant properties and oxidative stability are lost and potential toxic compounds, such as TFA and unsaturated aldehydes, are formed.     

Changes during heating in chemical composition and in-vitro digestion of four commodities

The effects of duration of heating on the composition and digestibility of whole cotton seed, almond hulls, whole pressed safflower seed and alfalfa were studied. The four commodities were heated at 125°C from 0 to 120 h. Nitrogen and ash values were relatively stable across commodities and heating times. However, acid detergent fibre, neutral detergent fibre, in-vitro neutral detergent fibre remaining after 48 h fermentation and acid detergent insoluble nitrogen increased hyperbolically, approaching a relatively constant value at long heating times for all commodities. The sensitivity of each commodity to heat damage was different, and the rate that each analysis value approached a relatively constant value differed across commodities. In general, alfalfa was the most sensitive and whole cotton seed the least sensitive for a given nutrient change with heating time. Also the amount of neutral detergent fibre digested approached a relatively constant value at longer heating times for whole cotton seed, whole pressed safflower seed and alfalfa while approaching zero for almond hulls. Prior analysis of an unheated commodity is necessary to utilise compositional analyses to determine heat damage.     

In vitro antioxidative and antigenotoxic capacity of wheat aleurone extracted with solvents

This study investigated the antioxidant and antigenotoxic ability of different wheat aleurone (WA) extracts. Oxygen radical absorbance capacity (ORAC), which was the highest in the aleurone ethanol extract (AEE) and the lowest in the acetone extract (AAE), was highly correlated with total polyphenol content (r=0.897, p<0.01). DPPH radical scavenging activity was highest in AAE followed by AEE and the aleurone methanol extract (AME). The ABTS^·+ quenching properties of the WA extracts were similar to their DPPH radical scavenging activity. Furthermore, WA extracts had a protective effect against oxidative stress-induced DNA damage in both human leukocytes and HT-29 human colon carcinoma cells. This inhibitory activity was attributed to their unique phytochemical content, with a strong correlation between DPPH radical scavenging activity and inhibition of DNA damage (r=0.779, p<0.01 at 10 ∝g/mL AAE). Therefore, WA might be a promising component of future nutraceuticals or value-added products.     

香蕉在不同冻结条件下的品质变化

探讨了香蕉分别经复合护色剂和热烫预处理后其在不同冻结温度分别为(-15、-25、-35、-45、-55、-70℃)条件下的冻结状态及其品质变化。复合护色剂与热烫预处理相比,随着冻结温度下降,香蕉在冻结过程其可溶性固形物、L值、p H值变化趋势及对细胞组织结构保护效果均优于热烫处理,结合光学显微镜观察香蕉组织切片,-35、-45、-55、-70℃时,冻结温度对香蕉细胞机械破坏程度无明显差异,综合考虑设备、成本等因素,采用复合护色剂预处理和-35℃温度条件冻结较适宜。     

Effects of iron,ascorbate, meat and casein on the antioxidant capacity of green tea under conditions of in vitro digestion

The hypothesis that interactions of dietary polyphenols with dietary iron occur during digestion and result in a decrease of the post-absorptive antioxidant properties of polyphenols was investigated. The hypothesis was tested in vitro, under conditions that simulate gastrointestinal digestion. Mixtures of green tea, iron, and three dietary factors that modify the form of iron in the lumen, namely ascorbic acid, meat or casein, were subjected to an in vitro gastrointestinal digestion. Antioxidant capacity (FRAP assay), iron concentration (ferrozine assay) and polyphenol concentration (Folin–Ciocalteau assay) were measured in the in vitro digests. The presence of iron decreased the antioxidant capacity and the polyphenol concentration of green tea digests. The presence of ascorbic acid increased, while meat and casein decreased the antioxidant capacity of green tea. The factorial analysis of the data suggests that protein and iron interact with green tea polyphenols during the in vitro digestion and decrease their antioxidant capacity. These results support the aforementioned hypothesis.     

Evolution of fermenting microbiota in tarhana produced under controlled technological conditions

The purpose of this study was to evaluate the evolution of lactic acid bacteria (LAB) and yeasts during the fermentation of tarhana produced with some pasteurised ingredients and carried out at 30 and 40 °C. The chemical parameters were those typical for tarhana production. Coliform bacteria were not detected during fermentation, while LAB and yeasts were in the range 10⁷-10⁸ colony forming units (CFU) g⁻¹. Plate counts showed an optimal development of both fermenting microbial groups and the differences in cell concentrations were not significant (P > 0.05). LAB were isolated during fermentation and grouped on the basis of phenotypic and polymorphic characteristics. LAB isolates were identified by a combined genetic approach consisting of 16S/23S rRNA intergenic spacer region (ITS) and partial 16S rRNA gene sequencing as Pediococcus acidilactici, Lactobacillus plantarum and Lactobacillus brevis. Hence, the pasteurisation of the vegetable ingredients, excluded wheat flour, enhanced the hygienic conditions of tarhana without influencing the normal evolution of LAB. However, the fermentation at 40 °C favoured pediococci, while the production at 30 °C was mainly characterised by lactobacilli. Yeasts, identified by the restriction fragment length polymorphism (RFLP) of the 5.8S ITS rRNA gene, were mainly represented by the species Saccharomyces cerevisiae in both productions.     

Decomposition kinetics of monoacyl glycerol and fatty acid in subcritical water under temperature-programmed heating conditions

The decompositions of monocaprylin, monocaprin, monolaurin and their corresponding fatty acids in subcritical water were measured under temperature-programmed heating conditions where the reaction temperature was linearly increased from room temperature to 350 °C at specified rates to estimate the activation energies E_i and the frequency factors k_i0 for the decompositions. The decompositions of both monoacyl glycerol and fatty acid obeyed first-order kinetics, and the decomposition of a monoacyl glycerol proceeded consecutively to form its constituent fatty acid and then further decomposition compounds. There was a tendency for both the E_i and k_i0 values for a monoacyl glycerol or fatty acid with a longer acyl chain to be smaller, and it was shown that the enthalpy–entropy compensation held for the decompositions of monoacyl glycerols and fatty acids as well as for those of fatty acid esters with various acyl and alkyl chains in subcritical water.     

Measuring the release of organic contaminants from melting snow under controlled conditions

The release of organic contaminants from a melting snowpack may result in temporary concentration peaks in receiving water bodies and respective pulse exposure of aquatic organisms. It is thus of considerable interest to gain a mechanistic and quantitative understanding of the processes determining the dynamic behavior of organic chemicals during snowmelt. Uniformly structured and contaminated snow was produced with the help of a newly designed snow gun and exposed to predetermined temperature conditions in a temperature-controlled cold room. The dry density and liquid water content during four freeze-thaw cycles was recorded continuously at different layers within the snowpack using time domain reflectometry, providing information on meltwater production and propagation as well as snow metamorphism. Fractionated meltwater samples were filtered and the dissolved and particle phase analyzed for five polycyclic aromatic hydrocarbons (PAHs) using gas chromatography/ mass spectrometry. The distribution of the PAHs between the dissolved and particulate fractions of the meltwater was strongly related to their hydrophobicity. Particle-bound PAHs were released late during the snowmelt, whereas PAHs in the dissolved phase were released uniformly during a two day melting period. Even though conductivity measurements indicated a preferential early elution of ions in the first meltwater fractions, no such "first flush" behavior was observed for soluble PAH. The developed laboratory-based approach opens up for the first time the possibility of reproducible experiments on organic contaminant behavior in snow. Future experiments will explore, in detail, how the properties of organic chemicals, the physical and chemical properties of the snowpack, and the temperature variations before and during the time of melting interact to determine the timing of chemical release from a snowpack.     

Effect of pH on cellulose digestion under in vitro conditions

The extent of cellulose digestion by rumen micro-organisms in vitro is dependent on the pH of the medium. Digestion is greatly reduced at pH values similar to those found within the rumen of sheep fed with diets rich in readily digestible carbohydrates. It is suggested that this may be one of the reasons for reduced digestion of the fibre component of forages when carbohydrate supplements are fed.     

Textural and morphological changes of Jasmine rice under various elevated cooking conditions

The effects of cooking at elevated temperatures (80, 100, 120 and 140 °C) and pressure levels (0, 0.1, 0.3 and 0.5 MPa) on the textural and morphological properties of cooked Jasmine rice were investigated. The developed high pressure cooker was utilized to process Jasmine rice in excess water under isothermal conditions. Rice cooking at higher temperature produced softer and stickier grain texture as well as more off-white colour. Using scanning electron microscopy technique, the microstructure revealed that the soft texture at high cooking temperature corresponded well to the increase of pore size and thickness of the sponge-like texture of inner layer endosperm. As the temperature increased, the outer layer of cooked rice became less porous. Boiling significantly altered the external appearance (namely colour and exterior integrity) and texture of cooked rice while cooking pressure had a little or no effect.     

The tinctorial stability of safflor yellow B under experimentally controlled model conditions

Several factors affecting the stability of safflor yellow B tincture were studied in experimentally scheduled model systems. Higher temperatures act on the colour more unfavourably than lower ones. UV light promotes bleaching of the pigment, pH is a decisive factor for preserving safflor yellow B, which deteriorated more rapidly under alkaline conditions. The pigment is sensitive to atmospheric O₂. Metal cations affect the stability of safflor yellow B: trivalent manganese and divalent iron reduce the orange-yellow colour most strikingly. The tinctorial stability and the practical utility of safflor yellow B are outlined on the basis of the experimental data.

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Die Farbstabilität von Safflor-Gelb B unter experimentell kontrollierten Modellkonditionen

Zusammenfassung In experimentell kontrollierten Modellsystemen wurden verschiedene Faktoren, die sich auf die Stabilität von Safflor-Gelb B auswirken, kontrolliert. Hohe Temperaturen und UV-Licht wirken bleichend. Das Pigment ist sehr pH-empfindlich, besonders im Alkalischen. Auch Sauerstoff zerstört es. Von den Metallionen wirken insbesondere Mn³⁺ und Fe²⁺ bleichend. Farbbeständigkeit und praktische Brauchbarkeit von Safflor-Gelb B werden diskutiert.

     

Fate of carbon tetrachloride during phytoremediation with poplar under controlled field conditions

The fate of carbon tetrachloride (CT) during phytoremediation with poplar was assessed by examining the transpiration of CT from leaves, diffusion from soil, tree trunks, and surface roots, and accumulation of chloride ion in soil and plant tissues. Feedwater containing 12-15 mg/L CT was added to the field test beds planted with poplar, and over 99% of the CT was removed. No significant amount of CT was transpired or diffused into the air, and no significant amount of CT-chlorine accumulated in the tree tissues. Chloride ion accumulated in the soil accounted for all of the CT-chlorine removed. When soils from the root zones were compared to unvegetated soils, microbial mineralization of CT was not enhanced in soils from the root zones as compared to unvegetated soils. Thus, we conclude that uptake and dechlorination of CT by plant tissues is likely the primary mechanism for phytoremediation by poplar.     

Polyphenols and antioxidant capacity of Phaseolus vulgaris stored under extreme conditions and processed

Phaseolus vulgaris is a foodstuff that not only supplies nutrients, but also bioactive compounds with antioxidant capacity; however, bad post-harvest storage or processing can diminish the antioxidant capacity. In this work, the effect of storage under extreme conditions, of thermal processing and of fermentation on the content of phenolic compounds and their antioxidant capacity (AA) in beans of just harvested P. vulgaris were evaluated. Combination of temperatures of 30 and 50 °C and relative humidity of 11% and 80% for 150 days were evaluated. Extreme storage conditions drastically decreased the AA, demonstrating that post-harvest storage at low temperature and humidity preserves the antioxidant capacity of the beans. Regarding processing, cooking decreased the scavenging effect and the AA by 63.5% and 56.8%, while fermentation decreased them by only 14% and 22%, respectively. It was concluded that the loss of antioxidant capacity due to heating is less in fermented beans.     

密封条件下冰温贮藏猪里脊肉的质构及理化特性变化

选取宰后4 h的新鲜猪里脊肉,以全质构(texture profile analysis, TPA)、挥发性盐基氮(total volatile base nitrogen,TVB-N)、色泽、pH值为参考指标,分别在第0、2、4、6、8、10、12、14、16、18天进行指标测定,综合评定冰温贮藏18 d内猪里脊肉品质变化。结果表明:随着贮藏时间的延长,猪里脊肉的硬度值下降(P0.01),咀嚼性逐渐降低(P0.05),弹性、内聚性和回复性变化不明显(P0.05),贮藏第6～8天,肉样TPA变化规律开始明显改变;TVB-N在贮藏期间逐渐升高(P0.01),在第16天达到二级鲜肉标准为15.62 mg/100 g;L~*值、a~*值、b~*值呈现出先升高后降低的变化趋势(P0.05),并在贮藏第12天出现最大值。因此,密封条件下冰温贮藏猪里脊肉色泽良好、肉质新鲜,可在不破坏细胞结构的基础上有效地延长了猪肉的贮藏期。