High pressure is used to texturize food with two different strategies. The first strategy consists of using high pressure of several hundred MPa as a gelling agent per se to replace any other gelling or coagulating agents. In the second strategy, a moderate pressure of 100-300 MPa is used as a pretreatment to modify the food components properties in order to improve the efficiency of the traditional texturing treatment such as heat texturization, acid or rennet coagulation of milk, and so on. In both cases, pressure effects depend on many parameters such as the nature and the concentration of the macromolecules, the temperature of pressurization, the holding time and pressure, the pH, and the presence of additives. The behavior of real foods upon pressurization is even more complex compared to that of macromolecular model solutions due to their complex composition and, especially, to the presence of enzymes which are sometimes hardly affected by pressurization. Findings exposed in this article demonstrate that high-pressure technology is a unique tool to texturize food and provide products with unique properties.
Electrons with energies of 300 keV or lower (soft-electrons) reduced microbial loads of grains, pulses, spices, dehydrated vegetables and seeds to levels lower than 10 CFU/g. The viscosity of gelatinized grain powder suspension (parameter for starch degradation) showed no significant difference between untreated grains and soft-electron treated ones, which indicated that soft-electrons did not significantly degrade the starch molecules of grains. Electrons with a higher energy with a higher penetration capacity resulted in a higher thiobarbituric acid value (TBA, parameter for lipid oxidation) of brown rice. Milling rice at a yield of 90% or 88% after electron treatment made the TBA of rice treated with electrons at 65 keV almost the same as that of untreated rice. The results indicated that the milling process removed the portion of brown rice exposed to soft-electrons. Seeds which were exposed to soft-electrons showed the same sprouting capacity as untreated seeds. Soft-electrons could eradicate microorganisms on the surface of dry food ingredients and seeds with little adverse effects on quality and sprouting capacity.
The effects of aged fermented bovine milk produced by a mixture of various lactic acid bacteria and a yeast, or a mixture of the lactic acid bacterium, Bifidobacterium longum, and a yeast on the proliferation activities of human carcinoma cells (DLD-1, MKN-1, and HL-60 cell lines) and human normal fibroblast cells (Fb) were investigated. Nonfermented bovine milk suppressed the proliferation activity in various degrees depending on the cell lines tested, suggesting that bovine milk may contain a component regulating in vivo proliferation of certain cells. The fermented milk produced by a mixture of various lactic acid bacteria and a yeast selectively reduced the proliferation activity of DLD-1 and MKN-1 cells. In contrast, the fermented milk produced by a mixture of B. longum and a yeast was selectively toxic to HL-60 cells, and cell proliferation activity was completely lost. Analysis of this cytotoxicity was revealed to be due to the induction of apoptosis which was demonstrated by the formation of apoptotic bodies and the fragmentation of DNA in treated cells. These findings strongly suggest that the cytotoxic factors affecting the viability of transformed and nontransformed cells are present in latent form in bovine milk, and these factors could be produced from milk by digestion using microbial enzymes.
Charts were prepared for estimating local maxima or minima of dimensionless, principal stresses of axial, radial, and tangential orientations formed in an elastic, cylindrical food during a drying or hydrating process. For this, analytical solutions derived previously were used. These charts showed that tangential stresses were the most critical for stress cracking during drying processes and radial stresses for hydrating processes. Sample applications of the charts were presented for adjusting process conditions to prevent stress cracking.
On-line measurement of sugar content in satsuma mandarins was already achieved using NIR transmittance spectroscopy. The feasibility of simultaneous measurement of citric acid content was investigated. The citric acid content determined by titration with NaOH and the second derivative absorption values autoscaled in the 710-930 nm region were analyzed by PLS1 using Unscrambler software. The spectra of peeled fruits measured by an NIR Systems Model 6250 were analyzed, and the model composed of 12 factors indicated the highest accuracy; R was 0.93, the mean residual (Bias) was -0.013% and the standard error of prediction (SEP) was 0.146%. The citric acid content in intact satsuma mandarins was regressed by the same method using an on-line instrument. The model composed of 5 factors calibrated from 689 samples showed the highest accuracy; R=0.83, Bias=0.024% and SEP=0.147% as a prediction result from 548 samples. It was possible to classify nondestructively the high acid fruits using near infrared (NIR) transmittance spectroscopy at about 20% error rate.
PTFE (polytetrafluoroethylene) membrane filters were tested for preparing corn oil emulsions by the membrane emulsification method using a pre-emulsified emulsion. A hydrophilic PTFE membrane was used to prepare an O/W emulsion without any disturbance of the continuous phase. A W/O emulsion was prepared with a hydrophobic membrane filter in the same way. The higher the flux of the pre-emulsified large particle emulsion via the membrane was, the higher the monodispersibility of the membrane emulsified emulsion became. There was no limit to the emulsifying pressure or the emulsifying rate under the conditions tested. The mean particle diameters of the O/W and W/O emulsions were ca. 3 times the mean pore size of the membrane used.
This study was conducted to determine the reason why dried rice cakes for non-glutinous rice crackers (Senbei) often break in the production process. Breakage after drying at 40°C for 12 h was found to be due to milling and storage conditions of the rice flour. Gel permeation chromatography revealed that the molecular weight of starch decreased as the extent of breakage increased. Damage to rice flour starch differed according to the milling methods. When press roller milled rice flour was stored at 5-25°C, the activity of α-amylase increased as the temperature became higher. The total water-soluble carbohydrate content of dried rice cake may be a good criterion to judge the extent of breakage. Reduction of the molecular sizes of starch, due to milling and action of α-amylase, is considered to cause the breakage of dried rice cake.
Enriching the atmosphere of fermenting “dhool” (macerated leaf) with oxygen led to faster production of some black tea volatile flavor compounds (VFC). There was a general rise in the total amounts of the VFC with long fermentation duration irrespective of whether it was done under enriched oxygen atmosphere or ambient air. The rise was, however faster under enriched oxygen atmosphere than under ambient air. The rise was also faster in the group I VFC than the group II VFC leading to a general decline in the Flavor Index with long fermentation durations. For every fermentation duration, the sum of group I VFC was higher under enriched oxygen atmosphere than under ambient air fermentation. Such variations were only marginal in the group II VFC. As a result, fermentation under enriched oxygen atmosphere reduced the aroma quality of black tea despite increasing the total amounts of VFC. Generally, the VFC which are oxidative products of amino acids and unsaturated fatty acids degradation increased with fermentation durations, while the major terpene alcohols declined under both ambient air and enriched oxygen atmosphere fermentation conditions.
The protective effects of (—)-epigallocatechin gallate (EGCg) and (—)-epigallocatechin (EGC) on paraquat-induced oxidative stress were compared in rats. Both EGCg and EGC effectively relieved decreases in food intake and body weight gain which were a result of administering the paraquat diet. The concentration of thiobarbituric acid-reactive substances (TBARS) in the liver of rats fed with the EGCg-added paraquat diet was lower than that of the EGC-added paraquat diet. The antioxidative enzyme activities in serum and liver, except for the catalase activity of the liver mitochondrial fraction, were not significantly different among the control, paraquat, paraquat+EGCg, and paraquat+EGC diet-fed rats. The catalase activity of the liver mitochondrial fraction was markedly decreased by feeding the paraquat diets and the decrease was strongly relieved by supplementing EGCg rather than EGC in the paraquat diet. On the other hand, decreases in the liver glutathione, cysteine and triacylglycerol concentrations that were caused by the paraquat diet had greater relief by supplementing EGCg rather than EGC in the paraquat diet. These results may suggest that the gallic acid moiety of the EGCg molecule plays an important role in demonstrating stronger protective effects for paraquat-induced oxidative stress.
Eggplant extract markedly inhibited melanogenesis in B16 mouse melanoma 4A5 cells (B16 cells). To clarify the characteristics of the melanogenesis inhibitor in eggplant, the effective fraction, P1, was separated from the eggplant extract by ammonium sulfate fractionation and Sephadex G-100 column chromatography. The P1 fraction from the eggplant contained 63% protein, 20% neutral sugar and 11% uronic acid. P1 was stable during heating at 60°C for 30 min, and the inhibitory effect remained stable after protease digestion. P1 weakly inhibited tyrosinase activity in crude B16 cell extract in vitro, and tyrosinase activity in B16 cells cultured with P1 was reduced. The regulation of tyrosinase activity in B16 cells was equal to melanogenesis suppression in B16 cells. These results show that the eggplant extract suppresses melanogenesis in B16 cells by regulation of tyrosinase.
The effects of triglyceride (TG) structure on the lymphatic absorption of dietary docosahexaenoic acid (DHA) were studied in lymph-cannulated rats using chemically structured TGs containing DHA. When 1,3-dipalmitoyl-2-docosahexaenoylglycerol (PDP) and 1,2(or 2,3)-dipalmitoyl-3(or 1)-docosahexaenoylglycerol (PPD) were administered to rats, DHA located at the 2-position in PDP was absorbed more efficiently in lymph than that at the 1(or 3)-position in PPD. Total fatty acid composition of lymph TG in rats given PDP and PPD was nearly similar, but the contents of DHA located at the 2-position of lymph TG were much higher in the PDP group than in the PPD group. HPLC analysis showed that the lymphatic TG composition in the PDP group was different from that in the PDD group. These results showed that the TG structure could influence the lymphatic absorption of dietary DHA.
L-Ascorbic acid (ASA) plays an important role in food and biological systems as an electron donor, and in the electron-donating process, ASA itself is generally oxidized to dehydro-L-ascorbic acid (DHA). The structure of DHA was reconfirmed to be monohydrated bicyclic structure in an aqueous solution. It was also clarified that DHA had the solvated bicyclic structure in methanol and ethanol solutions, and in these cases, the enantiomers were formed by the solvation of the C2 carbonyl group. When these solvated bicyclic DHA were dissolved in water, the solvent molecule on the solvated C2 carbonyl group was very easily replaced with a water molecule. From the results of MOPAC calculations, the heat of formation of C2 hydrated bicyclic DHA was estimated to be -299.2 kcal/mol, and DHA was clarified to be considerably stabilized by hydration. Furthermore, it was indicated that bicyclic DHA had more compact and less polar structure than ASA.