Effects of lamellar organization and arabinoxylan substitution rate on the properties of films simulating wheat grain aleurone cell wall

Herein, we evaluated the properties of alternate arabinoxylan (AX)/(1→3) (1→4)-β-D-glucan (BG) multilayer films. AX was extracted from wheat at three growth stages and single-component and alternate overlapping multilayer films were prepared. The physical properties, water diffusion rate, and water mobility of multilayer films during water absorption and desorption were studied. There were significant differences in the AX content and arabinose-to-xylose ratio at different growth stages. The LAX/BG multilayer films showed excellent thermal stability and mechanical properties with an increase in the relative humidity. The AX multilayer films with a low substitution rate showed a better water-binding capacity, whereas water molecules in films with a high substitution rate showed higher mobility. Therefore, a low substitution rate AX and AX/BG composite structure can improve the thermodynamic properties of multilayer films, but limit water mobility. We provide new insights on the physicochemical properties and water-regulation effects of wheat cell wall.

Quality Changes of Fresh Dumpling Wrappers at Room Temperature

In this paper, the quality changes of fresh dumpling wrappers during storage were studied by measuring the changes of microbial growth, color, pH, texture, cooking property, moisture content and distribution of raw dumpling wrappers. The correlation of these indicators was analyzed. The results showed that the dumpling wrappers had generated lots of microorganisms during storage and the pH value decreased gradually. The dumpling wrappers had browning and the color became darker. The texture of the dumpling wrappers changed obviously. The original structure of raw dumpling wrappers were destroyed, the water distribution is uneven and migration to the surface. The apparent index of raw dumpling wrappers has a significant correlation with the internal change, which provides a certain guiding significance for maintaining the good quality of dumpling wrappers.

Effect of ingredients on the quality characteristics of gluten free snacks

Grain-based fabricated snacks from non-wheat grains (amaranth, finger millet, sorghum and black gram) were used to prepare puffed snacks employing the method of hot air toasting. The functional characteristics and sensory attributes of the snack were determined by varying the moisture content and time of toasting. The quality attributes of the snacks like the instrumental color parameters, peak force and puff thickness of the snack correlated well with the sensory attributes (appearance/color, texture and overall acceptability). A snack made from amaranth showed a bright reddish brown colour at a moisture content of 20-40%; the product had a good puffing and high overall acceptability. The moisture content of all the snacks was around 3% and had a fat content of 1-2%; protein and dietary fiber contents were in the ranges of 22-23 and 10-11%, respectively. The principal component analysis (PCA) accounted for a total of 89.6% variation. The PCA biplot showed that sensory appearance, sensory texture and sensory overall acceptability were closely related to the puff thickness. The microstructure of the snack indicated the presence of air cells to offer a porous structure. On toasting, the flakes increased their thickness creating a porous microstructure such that the toasted snacks were crispy having a brittle texture. Popped sorghum and gelatinized starch added doughs exhibited good puffing when toasted at 20-30% moisture content while popped amaranth samples required higher moisture content (30-40%). The grain based gluten-free snacks with improved sensory and nutritional characteristics can be prepared by using different ingredients.

Water entry for the black locust (Robinia pseudoacacia L.) seeds observed by dedicated micro-magnetic resonance imaging

Water entry at germination for black locust (Robinia pseudoacacia L.) seeds which are known as hard seeds with impermeable seed coat to water, was examined using micro-magnetic resonance imaging (MRI). The MRI apparatus equipped with a low-field (1 T; Tesla) permanent magnet was used, which is open access, easy maintenance, operable and transportable. The excellent point of the apparatus is that T 1-enhancement of water signals absorbed in dry seeds against steeping free water is stronger than the apparatuses with high-field superconducting magnets, which enabled clear detection of water entry. Water hardly penetrated into the seeds for more than 8 h but approximately 60 % of seeds germinated by incubating on wet filter papers for several days. Hot water treatments above 75 °C for 3 min effectively induced water gap; scarification was 70 % at 100 °C and 75 °C, declined to 15 % at 50 °C and decreased further at room temperature. Water entered into the scarified seeds exclusively through the lens, spread along the dorsal side of the seeds and reached the hypocotyl, whereas water migrated slowly through hilum side to radicle within 3 h.

In situ study of water uptake by the seeds, endosperm and husk of barley using infrared spectroscopy

Variations in the amount and rates of water uptake influence the seed hydration as well as the modification of the endosperm for industrial uses (e.g., malting). The aim of this study was to investigate and interpret absorption frequencies in the mid infrared (MIR) region associated with water uptake in whole seeds, husk and endosperm of barley seeds during the initial period of soaking in water. Partial least squares (PLS) regression models for the prediction of water uptake in the set of samples yield a coefficient of determination (R(2)) and a standard error in cross validation of 0.75 and 2.57 (% w/w), respectively. The biological implications of this study are that the first stages of germination can be monitored using the information derived from the MIR spectra. These results also demonstrated that whole seeds, endosperm and husk derived from the same variety or genotype have different patterns in the MIR region.

Extraction, purification and identification of antifreeze proteins from cold acclimated malting barley (Hordeum vulgare L.)

Antifreeze proteins from cold-acclimated malting barley were extracted by infiltration-centrifugation. The infiltration time was optimised, and its extraction effect was evaluated. The effect of cold acclimation on the accumulation of barley antifreeze proteins (BaAFPs) was assessed by comparing the thermal hysteresis activities (THA) of proteins extracted from both cold acclimated and non-cold acclimated barley grain. Ultra-filtration, ammonium precipitation and column chromatography were used successively to purify the BaAFPs, and MALDI-TOF-MS/MS was used for protein identification. The results showed that infiltration-centrifugation was more targeted than the traditional method, and 10h was the optimal infiltration time. THA was observed only after cold acclimation implied that AFPs only began to accumulate after cold acclimation. After purification, BaAFP-I was obtained at an electrophoresis level and its THA was 1.04°C (18.0 mg ml(-1)). The mass fingerprinting and sequencing results indicated the homology of the BaAFP-I to alpha-amylase inhibitor BDAI-1 (Hordeum vulgare).

Role of seed coat in imbibing soybean seeds observed by micro-magnetic resonance imaging

BACKGROUND AND AIMS

Imbibition of Japanese soybean (Glycine max) cultivars was studied using micro-magnetic resonance imaging (MRI) in order to elucidate the mechanism of soaking injury and the protective role of the seed coat.

METHODS

Time-lapse images during water uptake were acquired by the single-point imaging (SPI) method at 15-min intervals, for 20 h in the dry seed with seed coat, and for 2 h in seeds with the seed coat removed. The technique visualized water migration within the testa and demonstrated the distortion associated with cotyledon swelling during the very early stages of water uptake.

KEY RESULTS

Water soon appeared in the testa and went around the dorsal surface of the seed from near the raphe, then migrated to the hilum region. An obvious protrusion was noted when water reached the hypocotyl and the radicle, followed by swelling of the cotyledons. A convex area was observed around the raphe with the enlargement of the seed. Water was always incorporated into the cotyledons from the abaxial surfaces, leading to swelling and generating a large air space between the adaxial surfaces. Water uptake greatly slowed, and the internal structures, veins and oil-accumulating tissues in the cotyledons developed after the seed stopped expanding. When the testa was removed from the dry seeds before imbibition, the cotyledons were severely damaged within 1.5 h of water uptake.

CONCLUSIONS

The activation of the water channel seemed unnecessary for water entry into soybean seeds, and the testa rapidly swelled with steeping in water. However, the testa did not regulate the water incorporation in itself, but rather the rate at which water encountered the hypocotyl, the radicle, and the cotyledons through the inner layer of the seed coat, and thus prevented the destruction of the seed tissues at the beginning of imbibition.

Water mobility in the endosperm of high beta-glucan barley mutants as studied by nuclear magnetic resonance imaging

(1)H NMR imaging (MRI) was used as a noninvasive technique to study water distribution and mobility in hydrated barley (Hordeum vulgare L.) seeds of accessions with varying content of beta glucan (BG), a highly hygroscopic cell wall component. High contents of BG in barley are unfavorable in malting where it leads to clotting of filters and hazing of beer as well as in animal feed where it hinders the rapid uptake of energy. However, a high content of BG has a positive nutritional effect, as it lowers the cholesterol and the glycaemic index. It was studied whether water distribution and mobility were related to content and location of BG. Water mobility was investigated by following the rate and mode of desiccation in hydrated single seeds. In order to determine the different water components, a multispin echo experiment was set up to reveal the T(2) transverse relaxation rates of water within the seeds. A principal component analysis (PCA) discriminated control seeds from the high-BG mutant seeds. MRI proved efficient in tracing the differences in water-holding capacity of contrasting barley seeds. All accessions showed nonuniform distribution of water at full hydration as well as during desiccation. The embryo retained water even after 36 h of drying, whereas the endosperm showed low and heterogeneous mobility of the water after drying. The relaxation time constants indicated that the BG mutants had regions of much higher water mobility around the ventral crease compared to the control. It is concluded that MRI can be applied to investigate temporal and spatial differences in the location of specific chemical compounds in single seeds.

Water uptake by dry beans observed by micro-magnetic resonance imaging

BACKGROUND AND AIMS

Water uptake by dry kidney beans (Phaseolus vulgaris 'Rajma') and adzuki beans (Vigna angularis) was traced using micro-magnetic resonance imaging in order to elucidate the channel of water entry, the manner of water delivery and the timing of swelling of the seeds.

METHODS

Magnetic resonance images of beans absorbing water were continuously measured with the single-point imaging method for 16 h or 20 h at 15-min intervals. With this technique, it was possible to detect and visualize the location of water in the beans, at a low water content, in the initial stages of water entry.

KEY RESULTS

Water was taken up through a specified tissue, the lens, near the hilum, and distributed primarily to the testa. When water reached the radicle, it began to be incorporated into cotyledons with considerable swelling of the seeds. Water uptake took place within a short time for kidney beans. The initial process of water entry was associated with mechanical vibration of the seed. Rapid hydration of the testa and the swelling of the cotyledons were then observed. Water was supplied to cotyledons through the adaxial epidermis. In contrast, it took a long time, approx. 7 h, to activate the water channel of the lens for adzuki beans which have a tightly fitting testa. Steeping of the testa was not uniform, which induced temporary slanting before enlargement of the seed.

CONCLUSIONS

The activation of the lens as the sole water channel, the delivery of water to the radicle within the testa, the swelling of the cotyledons, and the further increment of water are physiologically different processes during imbibition, and were separated by locating water in various tissues and by analysing the time course of water uptake using magnetic resonance imaging with the single-point imaging method.

Expression and inhibition of aquaporins in germinating Arabidopsis seeds

Extensive and kinetically well-defined water exchanges occur during germination of seeds. A putative role for aquaporins in this process was investigated in Arabidopsis. Macro-arrays carrying aquaporin gene-specific tags and antibodies raised against aquaporin subclasses revealed two distinct aquaporin expression programs between dry seeds and young seedlings. High expression levels of a restricted number of tonoplast intrinsic protein (TIP) isoforms (TIP3;1 and/or TIP3;2, and TIP5;1) together with a low expression of all 13 plasma membrane aquaporin (PIP) isoforms was observed in dry and germinating materials. In contrast, prevalent expression of aquaporins of the TIP1, TIP2 and PIP subgroups was induced during seedling establishment. Mercury (5 microM HgCl(2)), a general blocker of aquaporins in various organisms, reduced the speed of seed germination and induced a true delay in maternal seed coat (testa) rupture and radicle emergence, by 8-9 and 25-30 h, respectively. Most importantly, mercury did not alter seed lot homogeneity nor the seed germination developmental sequence, and its effects were largely reversed by addition of 2 mM dithiothreitol, suggesting that these effects were primarily due to oxidation of cell components, possibly aquaporins, without irreversible alteration of cell integrity. Measurements of water uptake in control and mercury-treated seeds suggested that aquaporin functions are not involved in early seed imbibition (phase I) but would rather be associated with a delayed initiation of phase III, i.e. water uptake accompanying expansion and growth of the embryo. A possible role for aquaporins in germinating seeds and more generally in plant tissue growth is discussed.

Water uptake and oil distribution during imbibition of seeds of western white pine (Pinus monticola Dougl. ex D. Don) monitored in vivo using magnetic resonance imaging

Dry or fully imbibed seeds of western white pine (Pinus monticola Dougl. ex D. Don) were studied using high-resolution magnetic resonance imaging (MRI). Analyses of the dry seed revealed many of the gross anatomical features of seed structure. Furthermore, the non-invasive nature of MRI allowed for a study of the dynamics of water and oil distribution during in situ imbibition of a single seed with time-lapse chemical shift selective MRI. During soaking of the dry seed, water penetrated through the seed coat and megagametophyte. The cotyledons of the embryo (located in the chalazal end of the seed) were the first to show hydration followed by the hypocotyl and later the radicle. After penetrating the seed coat, water in the micropylar end of the seed likely also contributed to further hydration of the embryo; however, the micropyle itself did not appear to be a site for water entry into the seed. A model that describes the kinetics of the earlier stages of imbibition is proposed. Non-viable pine seeds captured with MRI displayed atypical imbibition kinetics and were distinguished by their rapid and uncontrolled water uptake. The potential of MR microimaging for detailed studies of water uptake and distribution during the soaking, moist chilling ("stratification"), and germination of conifer seeds is discussed.

New Trends in Food Processing

In this work some of the newest trends in food processing are reviewed. This revision intends to provide an updated overview (including works published until February 2001) on the newest food processes, including food manufacturing, preservation, and control. Modern processes for food and food ingredients manufacturing based on membrane technology, super-critical fluid technology, and some applications of biotechnology are presented, mainly applied to obtain functional foods, "all-natural" enriched foods, probiotics and prebiotics. Also included is a critical assessment concerning non-thermal preservation techniques used for food preservation, such as high hydrostatic pressure, pulsed electric fields, ultrasound, pulsed light, hurdle systems, etc. Finally, a group of new analytical techniques (i.e., molecular techniques such as Polymerase Chain Reaction (PCR), food image analysis, and biosensors) and their use for food and process control is reviewed.