A new method of estimating the temperature in a food (sausage) exposed to dynamic temperatures was developed to predict bacterial growth in the food. First, the temperatures of nodes constructed in the sausage were successfully predicted from the measured temperatures of the surface nodes using the universal heat conduction equation. Second, to apply the method to real food industry contexts, the nodes for measurement were reduced to two standard nodes, namely, the centers of the top and bottom surfaces of the food. Temperature differences between the surface and standard nodes were mostly independent of the exposure temperature. Using the difference data and the temperatures measured at the standard nodes, the temperatures in the food exposed to various patterns of temperature were also successfully predicted. This method is thought to be empirical but practical. A new alert system which predicts the growth of microorganisms contaminating foods might be developed by coupling our method with a microbial growth model.
The aim of this study was to compare the inactivation effects of ohmic heating (internal heating by electric current) and conventional heating (external heating by hot water) on viable aerobes and Streptococcus thermophilus 2646 in milk under identical temperature history conditions. The effects of the two treatments on quality of milk were also compared by assessing degrees of protein denaturation in raw and sterilized milk (raw milk being sterilized by ohmic heating or conventional heating). It was found that microbial counts and calculated decimal reduction time (D value) resulting from ohmic heating were significantly lower than those resulting from conventional heating. There was no difference in degrees of protein denaturation during the two treatments. The results suggested that ohmic heating had not only a thermallethal effect, but also a nonthermal-lethal effect on microorganisms, due to the electric current. Based on the results, we propose that ohmic heating can be effectively used to pasteurize milk with no additional protein deterioration.
A novel method has been developed to measure the thermal conductivity of leaf-like material (tobacco) in the perpendicular direction to its surface over broad ranges of temperature and moisture with the aim of designing primary processes in the tobacco industry. Reduction in the time a sample is exposed to high temperature and humidity is a decisive factor because tobacco easily changes its nature under these conditions. A closed sample chamber with minimum volume permitted thermal conductivity measurements under these conditions without any significant deterioration in the sample. This method could also be applied to other wet materials that deteriorate easily. The thermal conductivity increased with both temperature and moisture and was regressed into two simple equations. It should become possible to estimate the heat transfer rate at desired temperatures and moistures when more extensive data become available. Consequently, a method for the measurement of the thermal conductivity of tobacco, which is one of the crucial factors in the rational design of primary processes, has been established.
Protein content and protein composition are considered very important factors in influencing the cooking and processing characteristics of rice. In the present study, the possibility of using near infrared reflectance spectroscopy (NIRS) to measure the protein composition (prolamin, globulin and glutelin) of rice flour was examined. The NIR spectra (1100-2500 nm) of a total of 119 rice flour samples with different protein compositions and particle sizes were acquired with a NIR spectrometer. Prediction accuracy of protein content was subsequently examined, revealing a similar accuracy (standard error of prediction (SEP) of 0.22%) to previous studies. NIR calibration models for determining protein composition were also examined using the partial least square (PLS) regression method. The best models were generated using multiplicative scatter correction-pretreated spectra, giving SEP of 0.18%, 0.06% and 0.25% for prolamin, globulin and glutelin, respectively. The findings show that NIR spectroscopy has the potential to serve as a rapid method for predicting the protein composition of rice flour.
6-O-Monoacyl ascorbates were synthesized by the condensation of L-ascorbic acid with caprylic, capric, lauric, myristic or palmitic acid using immobilized lipase in acetone. The decomposition processes of the acyl ascorbates in air were measured, and the decomposition kinetics were analyzed based on the Weibull equation. The rate constant, k, increased with increasing relative humidity and temperature for all acyl ascorbates; k also depended on acyl chain length, as the decomposition rates of ascorbates increased as acyl chains decreased. The enthalpy-entropy compensation held during the decomposition, suggesting that the decomposition of all acyl ascorbates proceeded by essentially the same mechanism. Furthermore, it was suggested that the oxidative degradation of the ascorbyl moiety of acyl ascorbate primarily proceeded during the decomposition, and was followed by the hydrolysis of the ester bond between the acyl and ascorbyl moieties.
The elution curves of caffeine, vanillin, coumarin, and methyl paraben, which have different hydrophobicities, in a bed packed with porous methyl methacrylate resin, were measured by the pulse response technique using methanol-water mixtures with various methanol contents as the eluent in the temperature range of 30°C to 200°C. The more hydrophobic solutes eluted at a slower rate under all conditions. All solutes eluted faster with eluents with higher methanol contents and at higher temperatures. The distribution coefficients of the solutes to the resin under various conditions were evaluated by moment analysis of elution curves. The adsorption enthalpy changes, ΔH, of the solutes were estimated from the plots of the distribution coefficients versus the reciprocal of absolute temperature. For the eluents with methanol contents higher than 75%, the ΔH values of all solutes were practically zero. This indicates that the solutes scarcely adsorbed on the resin. For eluents with lower methanol contents, solutes were eluted at a slower rate and their ΔH values were more negative. When water was used as an eluent, elution behavior showed the opposite tendency.
Although the carcinogenic effect of fumes produced during deep-fat frying has been well investigated, other toxic effects of these fumes have been little studied. In this study, a mixture of moisture and volatile compounds generated from a model system for deep-fat frying was collected for cytotoxicity evaluation using a series of connected ice and dry-ice traps. A system consisting of water-spraying-and-heating oil units was used as a model system for deep-fat frying. Chemical analysis of the trapped materials indicated that the main components were carbonyl compounds, and cytotoxicity evaluation revealed their cytotoxic activity on normal rat hepatocytes. The results of high-performance liquid chromatography analysis and cytotoxicity evaluation indicated that the main cytotoxic substances may be volatile aldehydes. The collection system used in this study could be useful to elucidate the toxicity of fumes generated from actual frying procedures.
We investigated the effects of L-ascorbic acid (AsA) on 11S globulin, which was reduced by 2-mercaptoethanol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis verified that AsA promoted the polymerization of 11S globulin via the formation of disulfide bridges. The generation of thiyl radicals (S·) in 11S globulin was examined by electron spin resonance spectroscopy coupled with spin trapping. The superoxide anion radical (O-2 ) was produced by the photoactivation of riboflavin. A typical line shape was observed for S·. Staining with nitroblue tetrazolium dye confirmed that O-2 was produced in the 11S globulin solution due to the autooxidation of AsA. Although the 11S globulin lacking AsA did not yield a rigid gel, the sample containing AsA successfully yielded a rigid gel. Thus, it is clear that O-2 generated during AsA oxidation exerts beneficial effects on 11S globulin in its reduced form.
The antioxidant activity of the polysaccharide from Ramulus mori and its derivatives (sulfated, phosphorylated, acetylated and benzoylated polysaccharides) were determined, including scavenging activity against superoxide, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals, reducing power and chelating ability. Obvious differences in antioxidant activity between the natural polysaccharide and its derivatives were observed, the antioxidant activity of the sulfated, phosphorylated and acetylated derivatives was stronger than that of the natural polysaccharide. In addition, the effect of temperature (20, 40, 60, 80 and 90 °C) and pH (3, 5, 7, 9 and 11) on the antioxidant activity of the natural polysaccharide and its derivatives was also investigated. The antioxidant activity of all samples in the linoleate emulsion improved with increasing from pH 3 to 11, while it decreased with ascending storage temperature from 20 to 90 °C.
Heterocyclic amines (HAs) are formed in protein-rich foods during high temperature cooking such as frying and grilling. The amount of HAs formed in several of the most frequently eaten food dishes in Korea such as Bulgogi (roasted beef), Galbi (grilled rib of beef), Samgyupsal (grilled boned rib of pork), fried chicken, charcoal grilled chicken and electrically grilled chicken, was determined. The ground-up samples were extracted under both acidic and basic conditions, cleaned on SPE cartridges, and the concentrations of fifteen HAs determined using electrospray ionization LC/MS. Limits of detection (LODs) and quantification (LOQs) were 0.99 ng g-1, and 3.33 ng g-1 for both MeIQ and Trp-P-1, and 0.51 ng g-1 and 1.67 ng g-1 for the remaining HAs. The absolute recoveries of the raw meat samples at a concentration of 3.33 ng g-1 (n=3) ranged between 60 and 100% for most of the HAs. The precision of inter-day assays was 1.0-15.3%. The range of inaccuracy for inter-day assays was -18.2 to 18.3% (bias) at a concentration of 25 ng g-1. Norharman, Harman, MeAαC and MeIQx were the amines the most frequently found in the cooked dishes, with concentration ranges of 17.4 - 261.0, 21.6 - 267, 3.61 - 27.7, and 6.45 - 20.8 ng g-1, respectively. While PhIP was the most frequently found HAs in the cooked pork (Samgyupsal) (5.2 - 17.2 ng g-1) and chicken breast (9.3 - 66.1 ng g-1), being present at high concentrations, it was detected in only one of the ten samples of cooked beef. Trp-P-2 was found in a few of the foods and its concentration was less than 5 ng g-1. In the investigation of the HAs contents according to the cooking method for the chicken breast, the highest amounts and frequencies of HAs, were found in the electrically grilled chicken breast, with 4,8-Di- MeIQx, 7,8-DiMeIQx and AαC being especially abundant. Since Bulgogi, Galbi, Samgyupsal and cooked chicken breast are the most popular meals among Korean people, regular consumption of such items may contribute substantially to their dietary intake of HAs.
We investigated the structure of fucoidan from Hizikia fusiformis. Using DEAE-Sepharose column chromatography, fucoidan was fractionated into four groups. F4, main fraction of fucoidan, contained 38 % (w/w) of ester sulfate and had the simplest sugar component (L-Fuc: D-Gal=7:3). The structure of F4 was discussed using de-sulfation, 2D-NMR and methylation analysis and proposed as [→3)-α-L-Fucp-(1→3)-α-L-Fucp-(1→3)-α-L-Fucp-(1→3)-α-L-Fucp-(1→]n R=α-L-Fucp-(1→4)-α-L-Fucp-(1→ (50%a) or α-D-Galp-(1→4)-α-D-Galp-(1→ (50 %a). 58 % in molar ratio of the hydroxyl group is sulfated.
The aim of this study was to characterize the sensory properties and taste compounds of the fermented milk (FM) produced by two species of lactic acid bacteria, Lactococcus lactis and Streptococcus thermophilus for 16 hours, and to compare them with those of yogurt (YG) made from the same reconstituted milk by Lactobacillus bulgaricus and S. thermophilus. Sensory evaluation showed that the sourness of FM was significantly weaker than that of YG, and that the lactic acid content of FM was significantly smaller than that of YG. The sourness intensity of an organic acid solution reconstituted on the basis of analyses of organic acids in FM was significantly weaker than that of YG. From these results, differences in lactic acid content appeared to be related to differences in sourness intensity between FM and YG.
The antibacterial activities of 81 edible plants against the dental caries pathogen Streptococcus mutans were investigated. The fresh vegetative crude extracts were subjected to the paper disc method. Furthermore, in order to fractionate the active component, hexane, ethyl acetate and methanol extracts from freeze-dried samples were also examined. Antibacterial activities were positive in 17 samples, including cinnamon and Japanese ginger. Among these, the stabilities of the active components against heat treatment or storage at 4 °C for one week were also investigated. Following these treatments, the activities of balsam pear and garlic extracts were lost, while the active components in ginger, Japanese ginger, clove and cinnamon appeared. Samples of the genus Zingiberaceae, including Japanese ginger and ginger, contained abundant and stable antibacterial components acting against S. mutans.
The pigments produced by Monascus are a mixture that includes azaphilone pigments. We simultaneously analyzed the 11 identified compounds present in Monascus pigments, and showed that there was a large variety of components produced by different strains and under different culture conditions. For example, pigments of Monascus pilosus NBRC4520 grown in potato dextrose broth were mainly composed of xanthomonascin A and monascorubrin. Ethanol extracts from cultured cells tended to contain more monascin and ankaflavin, and the nitrogen source also influenced the composition of pigment components produced. Moreover MK-1, a mutant of M. pilosus NBRC4520 that produces high levels of lovastatin and pigments (Miyake et al., 2006ab), was found to produce large amounts of rubropunctamine, monascorubramine, monascin and yellow II.
In this study, we examined changes in radical-scavenging activity, as well as in ascorbic acid content, total phenol content and color, in 6 kinds of shredded vegetables during storage. Radical-scavenging activity, ascorbic acid content and total phenol content of red cabbage were initially higher than those of the other vegetables. In shredded vegetables stored at 10°C for 7 days under air or under nitrogen gas, radical-scavenging activity remained unchanged, but ascorbic acid in green pepper decreased in the first day and remained unchanged thereafter. Total phenolics also remained relatively constant in shredded vegetables during storage.
Traditional Chinese medicinal herbs have been used for thousands of years to treat numerous ailments. In recent years, these herbs have been the focus of attention due to their medicinal and pharmacological benefits. In the present study, 25 types of herbs commonly used in Chinese medicinal culinary diets were quantitatively investigated for their various antioxidant activities. Using the 1,1-diphenyl-2- picrylhydrazyl high pressure liquid chromatography and 2´-deoxyguanosine oxidation methods, the highest antioxidant activity was found in chrysanthemum (Ju Hua), followed by hawthorn (Shan Zha), licorice root (Gan Cao), hibiscus (Luo Shen Hua), cassia seed (Jue Ming Zi) and Chinese wolfberry (Gou Gi), while poria (Fu Ling) and adlay (Yi Yi Ren) contained the lowest antioxidant activity. The same trend was also observed for total phenolic content using the Folin-Ciocalteu method. Ascorbic acid and tocopherol were only detected in trace amounts, suggesting that phenolic compounds may be the main contributors to herbal antioxidant activities.
The dough characteristics of mixtures of wheat flour and potato starches from three different cultivars (Eniwa, Benimaru and Norin No. 1) were investigated using a Brabender farinograph. The water absorption of control wheat dough was higher than that for all mixture doughs and decreased significantly with increases in potato starch. The peak time of wheat flour-potato starch mixtures ranged from 21.0 to 22.5 min, with no large difference with increase of potato starch. Dough stability significantly increased with increase of potato starch. The increase of potato starch in the mixtures decreased the tolerances of mixing, indicating that they were weaker than the control flour. Breakdown time of mixtures tended to be the same as for control wheat flour up to 5 % potato starch, above which it increased significantly. Results are applicable to the substitution of potato starch in certain wheat-based foods such as noodles, breads, biscuits, and crackers.
When mice fed a high-cholesterol diet were given 0.5 ml of a solution of Adzuki polyphenols (Adzuki- PP; 4 mg/ml) for two weeks via a catheter, the atherosclerotic index of experimental mice was significantly lower than that of the control group, indicating a significant inhibitory effect of Adzuki-PP on serum cholesterol level. In addition, the fecal cholesterol level in the experimental group was significantly higher than that in the control group. Supplementation of Adzuki-PP to a concentration of 290 ppm lowered the solubility of micellar cholesterol in a concentration-dependent manner, indicating that Adzuki-PP inhibits cholesterol micellization. It was therefore suggested that the inhibitory effect of Adzuki-PP on cholesterol micellization in the digestive tract was associated with suppressed serum cholesterol levels.