Heat‐Moisture Treatment and Enzymatic Digestibility of Peruvian Carrot,Sweet Potato and Ginger Starches

The aim of this work was to study the effects of heat‐moisture treatment (27% moisture, 100°C, 16 h) and of enzymatic digestion (alpha‐amylase and glucoamylase) on the properties of sweet potato (SP), Peruvian carrot (PC) and ginger (G) starches. The structural modification with heat‐moisture treatment (HMT) affected crystallinity, enzyme susceptibility and viscosity profile. The changes in PC starch were the most pronounced, with a strong decrease of relative crystallinity (from 0.31 to 0.21) and a shift of X‐ray pattern from B‐ to A‐type. HMT of SP and G starch did not change the X‐ray pattern (A‐type). The relative crystallinity of these starches changed only slightly, from 0.32 to 0.29 (SP) and from 0.33 to 0.32 (G). The extent of these structural changes (PC > SP > G) altered the susceptibility of the starches to enzymatic attack, but not in same order (PC > G > SP). HMT increased the starches digestion, probably due to rearrangement of disrupted crystallites, increasing accessible areas to attack of enzymes. The viscosity profiles and values changed significantly with HMT, resulting in higher pasting temperatures, decrease of viscosity values and no breakdown, i.e., stability at high temperatures and shear rates. Changes in pasting properties appeared to be more significant for PC and SP starch, whereas the changes for G starch were small. Setback was minimized following HMT in SP and G starches.     

Mode of action and inhibition of polygalacturonase covalently bound to polysaccharide and glass carriers

Endo-polygalacturonase (EC 3.2.1.15.) from Aspergillus spec. is much changed as far as its mode of action and the interaction with vegetable inhibitors of pectinase (from green beans and cucumbers) are concerned when it is covalently bound to insoluble carriers (Sepharose, cellulose powder, macroporous glass and nonporous ballotinis). Whereas a 2% degradation of substrate by the soluble enzyme caused a 50% decrease of viscosity of citrus pectic acid, the comparable degradation of substrate was increased to a level of about 10% with the investigated polygalacturonase carrier complexes apparently independent of the properties of the carriers and the kind of binding of the enzyme. In contrast to this the higher degradation of substrate of 15 and 20% respectively which was further stated at a 50% decrease of viscosity is unambiguously connected with the carriers and is in direct correlation with the specific activity of the polygalacturonase carrier complexes. Contrary to the soluble enzyme the covalently bound enzyme produces more lower oligomerous galacturonic acids by an exo-mechanism or by multiple attack already at the beginning of the hydrolysis of pectic acid. During the final stage there is an enrichment of trigalacturonic acid besides mono- and digalacturonic acids independent of the state of solution of the enzyme. It could further be stated that the strong inhibition of the soluble endo-polygalacturonase by selected pectinase inhibitors which was described earlier is reduced by degrees with the enzyme covalently bound to the insoluble carriers.     

Molecular Structure and Physicochemical Properties of Acid-Methanol-Treated Chickpea Starch

The molecular structure and physicochemical properties of acid-alcohol-treated (0.36% HCl in methanol at 25°C up to 216 h) chickpea starch were investigated. The recovery for modified chickpea starch ranged from 82 to 91%. A significant decrease in the swelling power, pasting viscosity, and gel strength was observed upon treatment with acid-methanol; however, the granule morphology remained unchanged. Structural studies revealed preferential degradation of amylose and long-chain amylopectin during treatment and the same was attributed to cause alterations in the functional properties. Molecular studies further revealed that the lower content ratio of short-chains to long-chains of amylopectin in chickpea starch resulted in the faster degradation rate upon acid-methanol treatment. An exponential model was also developed from the average molecular weight data to illustrate the degradation kinetics of acid-methanol-treated chickpea starch.     

Low‐Temperature Blanching as a Tool to Modulate the Structure of Pectin in Blueberry Purees

Blueberry composition was characterized for 6 cultivars. It contains a good amount of dietary fiber (10% to 20%) and pectin (4% to 7%) whose degree of methylation (DM) is sensitive to food processing. A low temperature blanching (LTB: 60 °C/1 h) was applied on blueberry purees to decrease pectin DM, in order to modulate puree properties and functionalities (that is, viscosity and stability), and to enhance pectin affinity toward other components within food matrices. Fiber content, viscosity, pectin solubility, DM, and monosaccharide composition were determined for both pasteurized, and LTB+pasteurized blueberry purees. The results showed that neither the amount of fiber, nor the viscosity were affected by LTB, indicating that this treatment did not result in any significant pectin depolymerization and degradation. LTB caused a decrease both in pectin DM from 58–67% to 45–47% and in the amount of water‐soluble pectin fraction, the latter remaining the major fraction of total pectin at 52% to 57%. A LTB is a simple and mild process to produce blueberry purees with mostly soluble and low‐methylated pectin in order to extend functionality and opportunities for interactions with other food ingredients.     

Effect of pilot-scale aseptic processing on tomato soup quality parameters

Tomatoes are often processed into shelf-stable products. However, the different processing steps might have an impact on the product quality. In this study, a model tomato soup was prepared and the impact of pilot-scale aseptic processing, including heat treatment and high-pressure homogenization, on some selected quality parameters was evaluated. The vitamin C content, the lycopene isomer content, and the lycopene bioaccessibility were considered as health-promoting attributes. As a structural characteristic, the viscosity of the tomato soup was investigated. A tomato soup without oil as well as a tomato soup containing 5% olive oil were evaluated. Thermal processing had a negative effect on the vitamin C content, while lycopene degradation was limited. For both compounds, high-pressure homogenization caused additional losses. High-pressure homogenization also resulted in a higher viscosity that was accompanied by a decrease in lycopene bioaccessibility. The presence of lipids clearly enhanced the lycopene isomerization susceptibility and improved the bioaccessibility. PRACTICAL APPLICATION: The results obtained in this study are of relevance for product formulation and process design of tomato-based food products.     

Changes in starch during malting of finger millet (Ragi, <Emphasis Type="Italic">Eleusine coracana</Emphasis>, Indaf-15) and its in vitro digestibility studies using purified ragi amylases

Malting of finger millet resulted in a decrease in its starch content and an apparent increase in its amylose value. Scanning electron microscopy studies of ungerminated and germinated starches showed a pattern of granular hydrolysis, which was dependent on the size and shape; big granules appeared to be more susceptible than small granules. Malting did not affect the relative viscosity of starches isolated from ragi malts. Purified !-1 amylase was found to hydrolyze germinated ragi starches (24, 48, 72 and 96 h) to an extent of 50-60%, whereas for !-2 and !-3 amylases it was in the range of 50-55% and 60-70% respectively. Amylose contents of starches did not have any visible effect on the extent of hydrolysis. Maltotetraose was the major oligosaccharide produced by these enzymes from all the germinated starches after 15 min of hydrolysis. Higher oligosaccharides (degrees of polymerization of 8 and above) underwent further degradation after 120 min hydrolysis.     

Structural characteristics and rheological properties of plasma-treated starch

Corn starch was treated by a dielectric barrier discharge plasma, and the changes in the granule morphology, crystalline structure, and molecular structure, as well as the rheological properties, were investigated using diverse techniques. Dielectric barrier discharge plasma could change not only the granule surface but also the internal structures of the starch granule through its pinholes. Specifically, after the plasma treatment, as the pinhole diameter increased, the relative degree of crystallinity decreased, accompanied by molecular chain oxidation, i.e., the generation of carboxyl groups, and degradation, i.e., molecular weight reduction. Therefore, the rheological behavior changed from pseudo-plastic to Newtonian with a decrease in the paste viscosity. The results indicate that dielectric barrier plasma could be used to produce modified starch with low viscosity at a high concentration for food and non-food applications.Industrial relevanceAs an eco-friendly and non-thermal physical technique, dielectric barrier discharge plasma has attracted great attention in polymer modification due to the interest in reducing generated wastes during modification and producing polymer products with high safety. Starch is traditionally a main material for foods and has been widely used in food and non-food industries. For improving the properties of starch and thus widening its industrial applications using a specific technique, it is indispensible to understand how the technique affects starch's structure and property. The present work revealed that not only was the surface of starch granules altered by the dielectric barrier discharge plasma but also the internal structure was affected, since the pinholes promoted the penetration of the plasma into granule interior. In particular, along with a reduced degree of crystallinity, molecular chain oxidation and degradation occurred, as confirmed by the generation of carboxyl groups and the molecular weight reduction. Then, the rheological behavior of starch paste changed from pseudo-plastic to non-Newtonian, together with a decreased paste viscosity. These results have demonstrated that dielectric barrier discharge plasma could be used as a new physical method to modulate the structure and rheological properties of starch, for the production of starchy food products with relatively low viscosity at a high concentration.     

Optimizing the Enzymatic Maceration of Foliole Purée from Hard Pieces of Hearts of Palm (Euterpe edulis Mart.) using Response Surface Analysis

Response surface analysis was applied to investigate modifications in viscosity of foliole purée treated with commercial enzyme preparations high in cellulase and endopolygalacturonase (pectinase) with changes in enzyme concentration (0.3–1.2%), incubation time (3.3–6.7 hr) and temperature (40–50°C). Foliole purée was obtained by trituration of hard pieces of hearts of palm (Euterpe edulis) and incubated in a rotating agitator. After treatment with 0.81% cellulase for ～5 hr at 50°C, a fourfold reduction in viscosity was found relative to a control sample. The minimum viscosity for this treatment was within the experimental range investigated. Optimized experimental conditions for treatment with pectinase however were outside the experimental range. The application of the cellulase preparation to the purée resulted in a 10% increase in yield of edible palm.     

Influence of heat–moisture treatment and annealing on functional properties of sorghum starch

Sorghum starch was annealed in excess water at 50 °C for 24 h. Starch was also modified under heat–moisture treatment at 110 °C after adjusting various moisture contents (20, 30 and 40%) for 8 h. Significant decrease in chain lengths of amylose fraction in HMT starches was observed. Heat moisture treated (HMT) and annealed (ANN) starches showed lower granule sizes, swelling power, peak and setback viscosity but higher retrogradation as compared to native starch. HMT starch with addition of 40% moisture showed a decrease in relative crystallinity. HMT and ANN starch gels were observed to be harder than native starch gel.     

Oxidation Effects in a Freeze-Dried Gelatin-Methyl Linoleate System

SUMMARY– We studied oxidation of a freeze-dried model system consisting of methyl linoleate and gelatin by incubating the model system in air at 50°C for up to 10 days in the dry state or at controlled relative humidities. Incubation for 5-10 days caused a drop in the viscosity of gelatin solutions, an increase in the solubility of gelatin in ethanol-rich solvent mixtures, an increase in the retention time of gelatin on a Sephadex G-150 column, and a reduction in the melting point of a standard gelatin gel. There were no such changes in the viscosity and solubility properties of gelatin when incubation was at a relative humidity of approximately 60%. In some instances, incubation at high relative humidity led to partial insolubilization of gelatin in water or in acetate buffer. The oxidation effects in the dry state were consistent with the hypothesis that gelatin undergoes oxidative degradation. The effects of oxidation showed similarities to effects of ionizing radiations.     

Role of initial apparent viscosity and moisture content on post irradiation rheological properties of guar gum

Guar gum is a polygalactomannan used in various industries. Previous studies on radiation processing of guar gum showed a decrease in its viscosity during irradiation. Present work reports rheological properties and magnitude of depolymerization as affected by initial apparent viscosity (AV) and moisture contents of guar gum during irradiation processing. Rate of degradation was found to be dependent on the initial moisture content of guar gum during irradiation. D₅₀ values for oven dried gum was 490 Gy and it increased to 1250, 2600 and 2420 Gy in samples having 10%, 25% and 30% initial moisture respectively. EPR spectroscopy showed disappearance of anisotropic signals with increasing moisture content indicating crosslinking of polymer. FTIR spectroscopy results suggested that there were no major chemical functional group transformations during irradiation.     

Change in colour and rheological behaviour of sunflower seed oil during frying and after adsorbent treatment of used oil

Improvement in colour and viscosity of used sunflower seed oil was studied because the reuse of recovered oil could provide considerable savings to food processors. In this study, 50 consecutive deep-fat fryings were done by using potato samples in sunflower seed oil at 170 °C. Significant changes in sunflower seed oil were observed during frying. Change in viscosity and Hunter colour parameters were investigated. These parameters were determined on oil samples taken periodically during frying, and after adsorbent treatment. A predetermined optimum adsorbent mixture (2% pekmez earth, 3% bentonite and 3% magnesium silicate by weight) was applied for colour and viscosity recovery of used oil. Both the adsorbent-treated and untreated used oils showed Newtonian behaviour. Significant increase in oil viscosity was observed during frying. Frying caused a decrease in Hunter L value and an increase in a, b and TCD values of used oil samples. Adsorbents improved the Hunter L, a and b values significantly as well as TCD values, but not the viscosity of the used oil. All the Hunter parameters and TCD followed zero order reaction kinetics. Good agreement was observed between calculated and measured data (r=0.986–0.996).     

Study of albedo and carpelar membrane degradation for further application in enzymatic peeling of citrus fruits

The enzymatic activity of four commercial enzymatic preparations (Peelzym I, II, III and IV) on citrus pectin, polygalacturonic acid and carboxymethylcellulose was determined (measured as the decrease in relative viscosity). In addition, the effectiveness of these preparations in the enzymatic degradation of the albedo and the segment membrane from Cimboa fruits was assessed. The highest activity on citrus pectin was shown by Peelzym II, although Peelzym I and IV activities were also elevated, 94.5 ± 6.2% and 88.7 ± 8.3% respectively of Peelzym II activity, and no relevant differences were found between them. Peelzym II also showed the highest activity for polygalacturonic acid, which was approximately 25% more than that of Peelzym I and IV, and more than double that of Peelzym III. Peelzym IV showed 40% more EM‐cellulase activity than Peelzym I, II and III. Segment membrane solution was degraded mainly by the enzymatic preparations Peelzym I and II. Thus, the most effective activities for the degradation of the carpelar membrane from Cimboa were those activities which act mainly on pectin and especially on polygalacturonic acid. However, the albedo was degraded to the greatest extent by Peelzym II and, in turn, the most important activities for albedo degradation were those which act on polygalacturonic acid. In addition, the concentration of the enzymatic preparation for the degradation of the carpelar membrane was lower than that required for albedo degradation. Copyright © 2004 Society of Chemical Industry     

Non-starch polysaccharides and bound phenolic acids from native and malted finger millet (Ragi,Eleusine coracana,Indaf - 15)

Nature of non-starch polysaccharides (NSP) and bound phenolic acids from native and malted ragi were studied using a recently-released hybrid variety of ragi, (Indaf-15). Yields of water-soluble NSP, hemicellulose-B and cellulose polysaccharides increased upon malting whereas a substantial decrease in the yield of hemicellulose-A was observed. Hemicellulose-B is the most viscogenic and its relative viscosity decreased from 3.04 to 1.98 upon 96 h of malting, whereas the solubility and viscosities of the rest of the NSP increased upon malting. The major sugars identified in all the NSP fractions were arabinose, xylose, galactose and glucose. A one- to two-fold decrease in arabinose was observed in all the NSP upon malting except for the alkali-insoluble residue wherein a decrease of glucose was observed. A progressive decrease in the pentose to hexose ratio was observed, indicating mainly pentosan degradation during malting, whereas an increase in the pentose to hexose ratio was observed in the alkaline-insoluble residue (AIR). Ferulic, caffeic and coumaric acids were identified as the major bound phenolic acids in native ragi and one- to two-fold decrease was observed in their contents after 4 days of malting.     

EFFECT OF AMYLASE ACTIVITY ON STARCH PASTE VISCOSITY AND ITS IMPLICATIONS FOR FLAVOR PERCEPTION

The viscosity of starch pastes prepared from waxy maize and wheat starches was measured as a function of concentration. Concentrations at which the two starches had comparable viscosities were selected and the decrease in viscosity with time on amylase addition was determined at 37C using a rapid viscosity analyzer (RVA). At the same level of enzyme addition the decrease in viscosity with time was much faster for waxy maize starch compared to wheat starch. For the latter, the time for the RVA viscosity to be reduced to half its value was of the order of 10 s. Volatile release was substantially increased with amylase addition. It is suggested that, at comparable initial viscosities, starch‐thickened products have better flavor and taste perception than products prepared with other thickeners because of the in‐mouth viscosity decrease resulting from amylase degradation. This could be explained by a reduction in perceived viscosity, which may enhance flavor perception as a consequence of signal processing within the brain, and/or an increase in the concentrations of volatiles reaching the olfactory receptors.     

Mashing Studies with Unmalted Sorghum and Malted Barley

The effects on wort quality when mashing with unmalted sorghum (0–100%) and malted barley (100–0%) in combination with industrial enzymes were evaluated. A mashing program with temperature stands at 50°C, 95°C and 60°C was used. Different combinations of commercial enzymes were evaluated. A heat stable α‐amylase was found to be essential for efficient saccharification. The inclusion of a fungal α‐amylase in mashes with a high sorghum content improved filtration rates to that of 100% malted barley mashes. Addition of a bacterial protease increased the amount of nitrogen solubilisation and peptide degradation. An increase of the relative proportion of sorghum in the grist resulted in decreases in wort filtration, colour, viscosity, attenuation limit, free amino nitrogen, high molecular weight nitrogen, and a corresponding increase in pH (p < 0.01). Overall the addition of malted barley in small proportions to unmalted sorghum mashes together with commercial enzymes was found to improve the potential for brewing a high quality lager beer from unmalted sorghum.     

Cerro Negro bitumen degradation by a consortium of marine benthic microorganisms

Cerro Negro bitumen, separated from an Orimulsion sample, was incubated for up to 120 days with sediments collected at a petroleum-impacted site in Tampa Bay, Florida. Biodegradation conditions were optimized by increasing bitumen surface area, continuous agitation on a shaker apparatus, use of a complete growth medium, and maintenance at 37 degrees C. Aerobic degradation conditions were promoted by maintaining sediment contact with the laboratory atmosphere. Bitumen recovered in solvent extracts when compared to autoclaved controls decreased by up to 40% during the first 56 days. There was no detectable change after this. Molasses addition and use of a culture enriched from the sediments did not change the extent or rate of decrease in bitumen recovery. Chemical fractionation of bitumen control and degraded bitumen showed that aromatic and aliphatic fractions were depleted by approximately equals 50%. Accumulation of polars was observed; however, the apparent increase was relatively small when compared to the mass loss of the other fractions. Selected biomarker ratios were not affected by incubation indicating their utility for fingerprinting the source bitumen in environmental samples. PAH distribution in the aromatic fraction favored the higher alkyl-homologues with the relative degree of alkylation increasing as the mass of bitumen recovered decreased with degradation. The study showed that up to 40% of the bitumen was bioaccessible and that bioremediation may be a treatment option for sediments contaminated with bitumen by an Orimulsion spill.     

焦磷酸钠对腺嘌呤核苷三磷酸解离氧化肌动球蛋白的影响

研究焦磷酸钠（sodium pyrophosphate,TSPP）对肌动球蛋白的氧化和解离程度,及对腺嘌呤核苷三磷酸（adenosine triphosphate,ATP）解离氧化肌动球蛋白效果的影响。结果表明,TSPP处理能抑制蛋白适度氧化（1?mmol/L?H2O2）,但氧化程度加深（10、20?mmol/L?H2O2）时抑制不明显。TSPP和ATP分别处理时,未氧化肌动球蛋白的特性黏数分别下降了30.4%和41.9%,平均粒径分别下降了21.2%和48.4%。二者相继处理后,特性黏数和平均粒径反而上升。所有氧化样品中由ATP引起的相对黏数变化量几乎都稍高于未氧化样品,但TSPP处理使升高幅度减弱。无论是否经过ATP处理,TSPP样品中均存在未解离且呈纤维状的肌动球蛋白,氧化后形成大的聚集物。可见,TSPP解离效果远不及ATP,且能抑制ATP的解离作用,氧化在一定程度上能促进ATP解离,但受TSPP抑制。研究结果为利用TSPP改善肉制品品质提供了理论依据。     

Physicochemical Characteristics of Brown Rice as Influenced by Gamma Irradiation

Brown rice samples prepared from medium grain (Mars) and long grain (Lemont and Tebonnet) varieties were irradiated at 0, 1.0, 2.0 and 3.0 kGy and analyzed. The amount of solids leached upon cooking increased with increased dose levels indicating the degradation of the rice grain structure. Damaged starch for Mars decreased to the 1.0 kGy level and increased thereafter. Moisture content remained constant between 13% and 14%. Amylose content was not greatly affected by irradiation. Peak viscosity, setback values, final viscosity, viscosity at 50°C, and consistency all decreased with increasing levels of irradiation. As radiation increased, an increase in the yellow color of the rice samples was noted.     

Influence of Heat Pretreatments of Oat Grain on the Viscosity of Flour Slurries

Heat treatment of oat grain had significant effects on the viscosity of flour slurries. Steamed oats produced highly viscous flour slurries, whose viscosity increased with time, whereas the viscosity of flour slurries produced from raw or roasted (104°C for 120 min) oats was much lower and degraded rapidly. Slurry viscosity was correlated with (1→3), (1→4)-β-D -glucan concentration in the flours and treatment of slurries with lichinase lowered viscosity significantly. Effects of steaming were partially reversed by roasting treatment and vice versa. Mixtures of equal amounts of raw and steamed flour resulted in slurries more viscous than either flour alone, but that viscosity degraded after 3 h to less than the mean viscosity of the steamed and raw controls. Water-soluble extracts from steamed flour had about twice the viscosity of raw or roasted flour extracts, but contained only 80% of the (1→3), (1→4)-β-D -glucan present in those extracts. Molecular weight analysis of soluble carbohydrates from raw, roasted and steamed soluble extracts indicated the molecular weight of β-glucans in these extracts was similar. However, if extracts were made from slurries that had incubated for 3 h, extensive degradation of β-glucans was evident in raw and roasted samples. It is likely that enzymic degradation of (1→3),(1→4)-β-D -glucans is responsible for much of the decreased raw and roasted flour slurry viscosity over extended time periods, but different heat treatments appear to also affect (1→3), (1→4)-β-D -glucan polymer interaction. © 1997 SCI.