Evaporation of water was enhanced by ordinary frequency (60 Hz) high electric fields (HEF), and the effect was directly proportional to the extent of treatment, i.e., increased with time and electric field, and decreased with separating head distance. Alternating current (AC) wire electric field was more effective in promoting evaporation of water than all direct currents (DC) and AC (plate) electric fields. As a result of the higher rate of evaporation, AC (wire) HEF caused a reduction of 1.0°C in the surface temperature in water and 4.5°C in ethanol. Both evaporation rate and surface temperature were resumed after the electric fields were discontinued. Furthermore, the evaporation rates of water and ethanol were equal to the respective controls after 60 min and 100 min of electric field cutoff, respectively. Similarly, HEF was very effective in promoting evaporation even at higher concentration of sugar or salt solutions. Cut discs (size: φ20 mm×10 mm, ca. 174 g, placed 10 mm apart on aluminum-foil) of apple flesh were dried under AC (wire) HEF under ambient conditions (25°C, 35%RH), and the higher the fields, the faster was the drying. After 10.0 h drying, the moisture contents of samples treated with 0.0, 5.7, 7.9 and 10.0 kV alternating electric fields (20 mm head distance) were 4.2, 3.6, 3.4 and 3.1 kg/kg dry solid, respectively.
Fish meat emulsion was prepared from egg-white, very low lipid sardine meat, salad oil, and vinegar. Its flow property was investigated in relation to coalescence. The peak stresses at 0, about 10, and 200 s−1 (P1, P2, P3) represented the shape of the flow curve. During the initial 7 days, an increase in P1 and P3 was observed in the conventional emulsion composed of egg-white, salad oil and vinegar. An increase in P1 and P2 was observed in fish meat emulsion and in the fish meat matrix including egg-white and vinegar. The P1 increase was ascribed to the properties of the egg-white. During this storage period of fish meat emulsion, coalescence proceeded slowly. On and after 10 days, the P1 increased in the conventional emulsion, but it decreased in fish meat emulsion and in the fish meat matrix. The P1 decrease was ascribed to the properties of the fish meat. This P1 decrease was accompanied by rapid progress of the coalescence. The coalescence development depended on the change in ovalbumin at the interface and the flow property of the fish meat matrix.
Limonoid glucosides extracted from seeds of Shiikuwasha (Citrus depressa HAYATA) grown in Okinawa were separated by column chromatography and high-performance liquid chromatography (HPLC), and then analyzed by thin layer chromatography, HPLC and nuclear magnetic resonance spectrometry. The 17-β-D-glucopyranoside derivatives of nomilin, limonin, deacetylnomilin and nomilinic acid were identified. The seeds contained 1.27 g of total limonoid glucosides per 100 g on a dry weight basis, showing two-fold higher levels than that found in other common citrus seeds.
Polyphenol oxidase was partially purified from aerial tubers of edible yam (Dioscorea opposita THUNB.). The enzyme strongly oxidized catecholamines such as dopamine and DL-noradrenaline. The optimum pH of the enzyme was 6.0 and its temperature was 30°C. The difference spectra produced a high positive peak at 300 nm during the enzymatic dopamine oxidation. Peak height (ΔA300) in the difference spectra increased in proportion to the reaction time for about 10 min at 30°C and pH 6. The ΔA300 value was found to be directly proportional to the dopamine concentration. A linear relationship was seen between the rate of dopamine oxidation (ΔA300/5 min) and the enzyme concentration. These results indicate that the difference spectrophotometric method is a useful way of rapidly and accurately determining catecholamine oxidase activity which is closely related to the enzymatic browning in edible yam.
1H-nuclear magnetic resonance (NMR) method using dioxane as the external proton standard was established to evaluate the quality of edible oils. The number of olefinic protons (OP) in oil was determined by the ratio of the integral value of olefinic protons (δH 5.33-5.47) versus that of methylene protons of dioxane (δH 3.4-3.5) using the solvent system of benzene-d6-30% MeOD (60°C). In this solvent system, good separation between the olefinic and methine protons from the triglyceride backbone was achieved. As a result, for various UV-irradiated oxidized rapeseed oils, the plots of the OP versus the iodine value and the plots of the number of divinylmethylene protons versus the 2-thiobarbituric acid value gave excellent linearity. In addition, the iodine values calculated by the proposed 1H-NMR method for five commercially available edible oils agreed with the experimental ones within ±3 iodine value error.
The angiotensin I-converting enzyme (ACE) inhibitory activity of fish sauce, the product with the strongest ACE inhibitory activity among liquid fermented foods, was fractionated into 2 fractions with ethanol treatment. The major part of the inhibitory substance was contained in the supernatant fraction (S-fraction) and its intraperitoneal administration had a hypotensive effect on spontaneously hypertensive rat (SHR). By octadecyl-silane column chromatography and two successive kinds of gel filtration, the inhibitory activity of the S-fraction was further separated into several fractions indicating that the strong inhibitory activity of the fish sauce is caused by a combined action of various kinds of inhibitory substances present. From the fraction with the lowest 50% inhibition concentration IC50 value, three kinds of dipeptides, glycyl-tryptophan, isoleucyl-tryptophan and valyl-tryptophan, were isolated as the ACE inhibitory compounds. Oral administration of these peptides to SHR showed a hypotensive effect.
Five sun-dried Kinema samples were collected from the eastern hills of Nepal and their proximate composition, mineral contents and amino acid compositions were analyzed. The Kinema contained 6.0±0.3% (mean±s.d., dry matter base) ash, and potassium comprised about 30% of the ash prepared from the Kinema sample. The average value of the trichloroacetic acid-soluble nitrogen (TCA-N) content relative to the total nitrogen content of the Kinema samples was 35.3% (s.d.=6.6). The percent liberation of amino acids (ratio of the sum of the free amino acid contents to the sum of the total amino acid contents) of the Kinema samples ranged from 6.0% to 16.5% with an average value of 11.4% (s.d.=4.3). When these values were compared with those of the Thua-nao sample obtained in Thailand and the Natto sample prepared in Japan, a higher TCA-N relative to total nitrogen was observed in the Natto sample. The pattern similarities of free amino acid compositions between the samples were calculated and showed that the samples were classified into 2 groups, the soybean sample and the group of the fermented soybean samples. The positions of the Kinema samples were closer to the position of the Natto sample rather than the Thua-nao sample.
Ten phenolic compounds; gigantol, moscatilin, tristin, crepidatin, 4-hydroxy-3,3',4',5-tetramethoxybibenzyl, 2,4,8-trimethoxyphenanthrene-3,7-diol, confusarin, moscatin, medioresinol and syringaresinol were isolated from Dendrobii Herba (stems of Dendrobium spp.), which is used as one of the important crude drugs for tonics, antipyretics and stomach agents, and their structures were elucidated on the basis of spectroscopic data. All of these compounds showed stronger antioxidative activity than BHA by the ferric thiocyanate method.
A direct titrimetric method for the determination of ethylenediaminetetraacetic acid (free EDTA) in foods is described. Free EDTA was extracted from food samples by equilibrium dialysis using ammonium buffer. An aliquot of dialyzate was subjected to direct titration with standard MgCl2 solution at pH 8.5 using Eriochrome Black T as a metallochromic indicator. The common inorganic ions (PO43—, NO3—, Cl—) and organic acids (citric acid, tartaric acid) in foods do not interfere with the proposed methods.
FSR, “Iwashinukazuke,” is a fermented fish product which takes over 6 months for ripening. The warmed brewing method is able to shorten the ripening period to 100 days. This study aims at obtaining fundamental qualitative knowledge of FSR using warmed brewing (30°C, relative humidity; 80%). The initial moisture (55.8%), NaCl content (31.2%) and pH (5.79) of FSR decreased to 51.0%, 26.3% and 5.20 after 100-days warmed brewing, respectively. TMA-N, VBN, NPN/TN and Amino-N/TN increased and the non-volatile amines of the FSR also increased during the warmed brewing. TBC, MYC and LAC at 100 days reached 8.7×107, 1.7×105 and 3.0×106, respectively. A sensory evaluation indicated that there was no particular difference except for color (rice-bran and meat) and flavor between the warmed FSR and the commercial FSR.
Quality changes in carrot slices, sticks, and shreds were not similar during storage at 0°, 5° and 10°C. The surface area per gram of tissue, respiration rate, and weight loss were greater with shreds than with slices or sticks. The total microbial count increased on all cuts during storage and the greatest increase was on shreds. Shear force of the sticks was greater than that of slices and shreds throughout storage. Chroma values for all types of cuts generally decreased during storage. These results indicate that carrot shreds quality cannot be maintained as well as that of slices and sticks during low temperature storage.
The effects of the concentration of the extract and the pH of the water phase on the partition between butanol and water of a crude extract from soybean seed hypocotyls were estimated. A seventy percent ethanol extract was dispersed in butanol-water (1:1) and each layer was subjected to thin layer chromatography and high performance liquid chromatography. A low concentration of the extract showed a high purity of saponins and a low partition ratio of soyasaponin I. At about pH 3.3, soyasaponin I was contained only in the butanol layer, and the partition ratio of soyasaponin I decreased with an increase in pH.
Volatile aroma compounds of mackerel samples (fresh, and frozen then stored for 5 days at 15±2°C (FR)) were analyzed by a dynamic headspace concentrator/gas chromatography/mass spectrometry (DHA/GC/MS) method. Compounds tentatively identified by MS were confirmed by comparing their mass spectra and GC retention times to those of standard compounds. Out of 65 peaks, 26 different volatile compounds were identified. Among the identified compounds were 4 aldehydes, 3 ketones, 10 alcohols, 2 esters, 3 alkanes, 3 sulfur-containing compounds and an acid. The aldehydes, ketones, alcohols, esters and alkanes generally give fresh fish aroma, whereas sulfur-containing compounds and acids give off-odors in mackerel. Although no sulfur-containing compounds were found in fresh mackerel, approximately 74% of the absolute peak area was occupied by dimethyl disulfide alone in FR mackerel.