The glass transition temperature Tg for many foods has been determined by thermal analysis such as differential scanning calorimetry (DSC). The thermal analysis, however, does not provide information on molecular mobility. In this review, the analysis of the glass transition of foods by electrical methods and proton-NMR was explained and compared with that obtained by DSC. The dielectric relaxation, i.e., the peak of the dielectric loss, e″, was observed for some glassy foods and ascribed to the local motion of molecules. The relaxation time τ and the activation energy Eact seemed suitable parameters to describe the enhancement effect of water on the mobility of molecules in the glassy state. However, when the ionic conductivity dominated the electrical properties, the e″ peak was masked. For analyzing such a system, the electric modulus, M* was an effective tool. The value of the activation energy obtained through M* formalism in the glassy state was larger than that in the rubbery state, probably due to a change in the free volume size by glass transition. For NMR research, the mobility of glucose syrup in the glassy and rubbery states has been examined. Free induction decay (FID) was measured with low-resolution NMR and was best fitted by a Gaussian lineshape multiplied by sinc function plus an exponential function. The T2 of mobile protons reached the rigid-lattice limit at a temperature lower than the midpoint Tg obtained by DSC.
A laboratory-scale parboiling setup was fabricated to produce parboiled rice at low steaming temperatures for determination of its physical properties, the quality indicators, and to compare those qualities with rice produced at higher temperatures. Parboiled rice was prepared under different steaming conditions using different sample sizes, both of which affected the rice temperature and quality. A sample size of 200 g, which maintained a 10 mm thick layer of rough rice, was found adequate for favorable quality. Better quality of parboiled rice was achieved at lower steaming temperatures (80–100°C) than that at higher temperatures (110 and 120°C). The temperature-time combinations of 80°C-40 min, 90°C-30 min and 100°C-20 min were recommended steaming conditions. Parboiled rice produced under these conditions has adequate lightness and color intensity, 4.0 to 7.5% more milling yield having 55 to 80 N hardness values compared with an untreated sample. It is believed the proposed parboiling method would be seen as important by both household and commercial parboiling plants in their production of a good quality product.
Differential scanning calorimetry (DSC) was used to determine the thermal properties of parboiled rice, and these properties, i.e. gelatinization parameters, namely, peak temperature (Tp) and residual gelatinization enthalpy (ΔH) were evaluated. The Tp increased and ΔH decreased with increase in the severity of heat treatment during the parboiling process. The physical property of color value correlated positively with the Tp and the degree of starch gelatinization correlated positively with the hardness of the parboiled rice. The Tp, which represents half the conversion temperature of the sample melting, is believed to be a suitable indicator to identify the severity of heat treatment in the parboiling process. The quantitative Tp values of 77.4 to 79.2°C corresponding to the processing conditions of 90°C-30 min and 100°C-15 min are viewed as an index for better quality of the rice. The thermal properties thus can be utilized to understand the cooking behavior of parboiled rice.
Food samples undergo various physical changes during long period refrigeration and their taste gradually diminishes. The amount of squeezable drip and salt-soluble protein in beef fillet and salmon meat were measured as indices of taste during the course of refrigeration and compared with sensory tests. Both meat samples showed similar degradation tendency. The amount of squeezable drip increased rather rapidly within 15 h, although the increase did not directly correlate with the sensory tests. The amount of salt-soluble proteins, which is one of the typical indices of denaturation of protein, decreased gradually with lengthening refrigeration period and was well consistent with the sensory tests. The mobility of water molecules in the food samples was examined by measuring the spin-spin relaxation time T2 measured by the CPMG method of pulse NMR. The spin echo signals of pulse NMR were analyzed by Gauss-Newton nonlinear regression analysis. The experimental curves were satisfactorily taken into account according to the two-component approximation in which each sample was assumed to contain two kinds of water components with different relaxation times, short- and long-T2. The relative amount of the short-T2 component corresponded well with the sensory tests and also with the decrease in salt-soluble protein that was representative of the texture items. It was concluded that the mobility of water molecules as determined by the relaxation times holds promising information to evaluate the degradation degree of meat samples during long-period refrigeration.
The effectiveness of a membrane process combining ultrafiltration (UF) and nanofiltration (NF) for purifying and concentrating non-digestible saccharides (NDS) from yacon rootstock was examined. The yacon rootstock used as experimental material contains, among various other agromaterials, a comparatively large amount of NDS, fructooligosaccharide (FOS) and inulopolysaccharide. After extraction with hot water followed by UF clarification and NF purification processes, the resulting NF retentate containing NDS in high concentration was obtained as a 25-fold concentrated product. NDS purity was ultimately raised from 81% to 98% by the combined membrane processes of UF and NF (with G10 membrane). HPLC analysis revealed that the NF membranes had specificity of rejection for saccharides of particular degrees of polymerization (DP). The rejection performance remained constant throughout the NF process. On the whole, the results indicate that the combined membrane-processing system is quite promising for value-added products using purified concentrate of NDS.
The application of supercritical carbon dioxide (SC-CO2) extraction to waste powder derived from sweetpotato roots with orange flesh in a food processing factory was examined. The contents of antioxidants, β-carotene, α-tocopherol and chlorogenic acid, remaining in the waste powder after SC-CO2 extraction under different conditions were determined by HPLC. At a constant extraction pressure, the extraction yield of β-carotene from the waste powder was highest at 40°C, decreased at 60°C and decreased further at 80°C; in contrast, the α-tocopherol yield did not vary under different temperature conditions. At a constant extraction temperature, increasing extraction pressure in-creased the extraction yields of both β-carotene and α-tocopherol. Under the conditions tested, the yields of β-carotene (95.1%) and α-tocopherol (76.8%) were highest at 40°C and 35 MPa. Little chlorogenic acid was extracted from waste powder. The β-carotene remaining in the waste powder after SC-CO2 extraction correlated well with its color value of a*.
Millers in Japan are aware that the apparent viscosity of heat-treated wheat flour paste is higher than that of untreated flour. Factors affecting flour paste viscosity must be known to obtain replicable viscosity data. Heat treatment was most effective at 110°C for 15 min using an autoclave. The apparent flour paste viscosity under specific conditions decreased as measurement time increased.
Influence of protein (Dairy LoTM )(DL) and carbohydrate based (NovagelTM)(NOV) fat replacers on the flavor volatiles of low fat Cheddar cheese (5% fat), during initial stage of ripening, were determined using Gas Chromatography-Mass Spectrometry. The predominant volatiles in all cheeses were; octanoic acid> acetoin > 2,3-butanedione. Undecanoic acid, nonanoic acid, and heptanone were less dominant. Treatments apparently attenuated them differently during initial aging compared to the low fat control (LFC) based on their relative ratio to an internal standard (12 μg of 3-heptanol/250 g of grated cheese). Within one month of maturation, the ratio of acetoin increased from 12.5 to 16, decreased from 15 to 13, and 11 to 9 for NOV, DL, and LFC, respectively. Octanoic acid, the most dominant volatile, decreased markedly in all cases in the order; 29 to 18>26 to 18>26.5 to 22, for LFC, NOV, DL, respectively. 2,3-Butanedione decreased to about half the initial concentration only for NOV and remained relatively the same for DL and LFC. Other comparatively minor volatiles were also impacted differently. These preliminary data show that fat replacers attenuated initial storage related flavor volatiles of low-fat Cheddar cheese compared to control and this influence varied depending on the type of fat replacer used.
A lactic acid bacteria drink from a vegetable (broccoli) with high nutritional value and various physiological functionalities was developed, and the preserving property of the drink was studied. When this the broccoli lactic acid bacteria drink was stored at 5°C and citric acid was added to it, the drink had a good taste and the number of lactic acid bacteria remained over 107 CFU/ml for about 10 days. In addition, the broccoli pasteurized lactic acid bacteria drink was developed in order to extend the storage time. The lactic acid bacteria were sufficiently killed after heating at 75°C for 40 min, when pasteurization condition of the lactic acid bacteria drink was examined. However, vitamin C content was lowered to about 60%. Then, when erythritol was added to the pasteurized lactic acid bacteria drink, the storage time was extended to 3 weeks, and the taste and aroma also improved. We found the fact that the broccoli pasteurized lactic acid bacteria drink suppressed the increase in acetaldehyde, ethanol and acetic acid which cause to the quality deteriorate in storage.
The growth condition of Lactobacillus amylovorus strain JCM 10628, an amylolytic lactic acid bacterium, was tested as a source of enzymes for saccharifying boiled rice to produce a beverage similar to Amazake, a traditional non-alcoholic beverage. The composition of a medium that should leave no unpleasant taste in the Amazake-like product was confined to 1.0% raw cornstarch, 2.0% skim milk, and 0.1% yeast extract. α-Amylase activity and cell growth de-creased in the medium lacking any of the three ingredients. Production of α-amylase was stimulated by soluble starch as well as raw cornstarch, but neither by glucose nor sucrose. When 100 ml of the culture broth was mixed with 16 g of rice after boiling and incubated at 55°C for 24 h, the obtained fluid had an acceptable sweet and sour taste.
The effect of substitution of waxy-wheat flour (WWF) for common wheat flour, ‘Hermes’ on dough and baking properties was determined. Flours consisting of 20% WWF and 80% Hermes (20 WWF) and 40% WWF and 60% Hermes (40 WWF) were used. Two other mixed flours were prepared for comparison: one consisted of 20% Chinese spring flour (CSF) and 80% Hermes (20 CSF) and the other of 40% CSF and 60% Hermes (40 CSF). Breadcrumbs became softer with increasing WWF substitution, and harder with increasing CSF substitution. From cross sections of these breads from 20 WWF and 40 WWF, the partial substitution of WWF for Hermes was considered favorable for baking results. Especially, 40 WWF made larger loaves and improved glutinous texture, such as the chewing property or adhesiveness of breadcrumbs, as compared with Hermes alone. DSC data showed that WWF retarded the staling of breadcrumbs during storage and also accelerated the refreshing of breadcrumbs with softness and glutinous texture after reheating. Substitution of WWF decreased the setback of viscosity under the holding temperature and suppressed the gelation of starch under cooling, both of which improved the pasting property of starch. In addition, WWF appeared to suppress the formation of an insoluble network structure of starch during cooling, which improved the tolerance of gelatinized starch to the retrogradation. These results indicate that the partial substitution of WWF for common flour improved the softness and glutinous texture of breadcrumbs and retardation of staleness. Consequently, WWF might have applications in practical baking.
Enzymatic hydrolysates with antihypertensive activity were obtained from the leftover residues of a chicken essence factory. Among many proteases tested, Alcalase was found to be the best to produce high angiotensin I-converting enzyme (ACE) inhibitory activity in vitro. The in vivo experiment revealed that a 3% supplement of the Alcalase-treated hydrolysate of chicken essence residues added to the control diet fed to spontaneously hypertensive rat (SHR) lowered the systolic blood pressure (SBP) of the rats after 16 weeks of treatment and at 1 week post-treatment. Repression of ACE activity of the aorta was suggested to be the reason for the antihypertensive effect of the Alcalase-treated hydrolysate of chicken essence residues.
Quercetin glucosides ingested as components of a foodstuff can be transformed to quercetin, and the quercetin is oxidized by peroxidase in the oral cavity. One objective of this study was the characterization of the oxidation products. Although both salivary peroxidase and myeloperoxidase are contained in whole saliva, salivary peroxidase is mainly involved in the oxidation in the saliva. As the oxidation products, 2,3,5,7,3′,4′-hexahydroxyflavanone-like compound and two isomers of a compound, which was transformed to quercetin and the above flavanone by a HCl/heat-treatment, were isolated. 3,4-Dihydroxybenzoic acid and 2,4,6-trihydroxyphenylglyoxylic acid were also detected in the oxidation products. When dialyzed saliva was used, the salivary peroxidase-dependent oxidation of quercetin and the formation of the oxidation products were partly inhibited by 1 mM thiocyanate which was a substrate for the peroxidase in the oral cavity. The mechanism and the significance of salivary peroxidase-dependent oxidation of quercetin in the oral cavity are discussed.
We previously reported that the dietary ingestion of red bell pepper (Capsicum annuum L.) which contained a large amount of antioxidative carotenoids ameliorated the age-related phenomena of learning disorder and degradation of hair glossiness in the senescence-accelerated mouse (SAM). As lycopene is one of the most popular carotenoids in human serum and exists in abundance in tomato, we examined the effects of dietary lycopene and tomato rich in lycopene on the age-related disorders in SAMP8//Kgm, a mouse model of accelerated decline in learning and memory, and control SAMR1//Kgm mice. SAMP8 mice that received a diet containing 0.02% (w/w) lycopene or 20% (w/w) tomato powder showed much better acquisition in passive avoidance tasks than those given the control diet. Dietary lycopene and tomato had no effect on the ability of learning and memory in SAMR1 mice. Those observations indicated that the dietary ingestion of lycopene in tomato ameliorated the learning impairment in SAMP8.
The microbial transglutaminase (TGase) from Streptomyces libani was purified from its culture broth and its enzymatic properties were compared with those of TGase from Streptoverticillium mobaraense var. TGase was purified by ion-exchange chromatography and size-exclusion chromatography. The specific activity of the main component was 10.7 unit/mg protein, lower than that of Streptoverticillium mobaraense var. (25 unit/mg). Several differences of enzymatic properties were found between the two enzymes. Optimum temperature, stability and gelation activity of TGase from Streptomyces libani were lower than those of TGase from Streptoverticillium mobaraense var, while, deamidation activity was higher. In addition, the existence of some TGases with different pI were suggested.
SDF (soluble dietary fiber) and IDF (insoluble dietary fiber) fractions were extracted from 14 different foods by the modified Prosky method. Ion exchange chromatography with DEAE cellulose was employed to examine each of the fractionated sugars. Aloe fractions were further subjected to gel chromatography to examine the effect of heating on molecular weight. The SDF fractions of anhydrous samples of okra, cabbage, celery, bitter gourd, and carrot were large when autoclaved, while that of aloe was largest when unheated, and those of eggplant, edible burdock, Japanese radish, hijiki, and nameko were large when microwaved. The SDF fractions of moroheiya and okra included acid polysaccharides in large quantities, and acid polysaccharides increased further with autoclaving. The SDF fraction of celery did not show as pronounced a tendency for heat-induced increase of acid sugar. IR analysis confirmed that heating affected the functional groups of this fraction.
The anti-tumor promoting activities of 120 kinds of edible plants against the non TPA-type promoter, okadaic acid (OA), were investigated by measuring suppression of the inhibitory effect of OA on protein phosphatase-2A (PP2A), since OA promotes tumor formation by inhibiting this enzyme. One quarter of the tested samples showed activity over 20%. In particular, 8 kinds of plants (basil (100%), peppermint (100%), carrot leaf (100%), broccoli (100%), nabana (98%), edible burdock (86%), watermelon (99%) and winter fungus (100%)) showed very strong activity. Physicochemical properties of the active components contained in the samples that showed high activity were found that the active component in the major sample was inactivated by cold storage or boiling, and that only edible burdock showed strong activity following both types of processing. Soluble fractions from these samples were obtained by extraction in hexane, benzene, ethyl acetate, methanol and water. Very strong anti-OA activity was observed in water soluble extracts of edible burdock and eggplant, whereas cabbage and broccoli showed activity in the extraction fractions in organic solvents such as hexane. Although the active components in these samples were not identified, these findings suggest that the component with anti-okadaic acid activity must be present in edible plants.
The objective of this study was to evaluate the effects of high-molecular-weight glutenin subunits with different protein contents on the quality of flour. The flour properties of near isogenic lines (NILs), which were substituted with HMWG subunits at the Glu-B1 or Glu-D1 allele, were investigated with four levels of protein content. The effect of the addition of subunits 20 at the Glu-B1 to subunits 5+10 at the Glu-D1 allele on bread-making quality was poor. The strength of the dough was only slightly affected despite the increase in protein content. Subunits 2+12, subunits 4+12 and subunits 2.2+12 at Glu-D1 allele had little effect on dough properties when various protein contents were used, compared with subunits 5+10. Subunits 2.2+12 had the most negative effect on the physical properties of the dough at the Glu-D1 allele. These results clearly showed that each HMWG subunit affected the properties of the dough differently, according to the increase of protein content.