Frying is an important cooking process due to the unique palatability and sensory characteristics of fried foods. Fried foods contain a considerable amount of fat, and have a negative perceived image due to their high caloric value and increased consumer awareness of the relationship between food, nutrition, and health. Oil consumption and especially saturated fat, is considered as one of the principal factors increasing health risks of heart disease, cancer, diabetes, and hypertension. The mechanism of oil uptake during frying is complex and affected by numerous factors, such as product and oil composition, surface-active agents, etc. Frying oil undergoes three main deleterious reactions: oxidation, hydrolysis and thermal decomposition, resulting in the formation of numerous constituents. The latter affect the organoleptic characteristics of the fried product, and could pose health risks. Frying has a significant role in the overall nutritional value of the product. Compared to other cooking methods, retention of water-soluble vitamins and vitamin E could be higher after frying. Due to the deterioration of oil after prolonged frying, regulations on the maximum levels of polar compounds and polymer concentration have been utilized. Nevertheless, an alarming number of oil samples collected from restaurants and fast food outlets in Europe failed to comply with regulations. Frying has only a marginal affect on the concentration of trans fatty acids. Yet, due to their possible connection with heart disease, the initial concentration of hydrogenated fats (that could reach 50%) should be considered. The relationships between frying and carcinogenesis and mutagenesis are inconclusive. Cyclic fatty acid monomers, which can be formed during frying, were proven harmful only in some studies. Exposure to malondialdehyde (MDA) during typical consumption of fried food constituted no actual health hazard, although MDA is known to be a very potent mutagen and carcinogen. Heterocyclic amines, formed during fish and meat frying, were related to higher cancer incidence, but only in concentrations which were higher by several orders of magnitude than those formed in typical frying. It is concluded that based on information to date, and using good manufacturing practices, fried foods pose no significant health hazard in a balanced diet.
The effect of the combination of heating and pressurization on Maillard reaction was investigated using a model solution of glucose and glycine, and a white sauce. The apparent browning rates were calculated from the relationship between the treatment time and the absorbance of the model solution at 430 nm. The apparent activation volume was estimated from the relationship between the apparent browning rate and the pressure, and the apparent activation energy estimated from the rate and the temperature. High hydrostatic pressure (HHP) up to 400 MPa retarded the Maillard reaction in a temperature range of 100–115°C. The apparent activation volumes fell into 3.8–4.5 cm3·mol−1 in a temperature range of 100–115°C, and the apparent activation energies into 94.3–105.3 kJ·mol−1 in a pressure range of 0.1–400 MPa. The HHP treatment also suppressed the browning of the white sauce, which was heated at 115°C for 30 min under 300 MPa.
Pressure distribution during the chewing of food with molars was measured using a multiple-point sheet sensor, and compared with results from an instrumental compression test. The sensor system detected the masticatory pressure with many sensing cells so that masticatory force and contact area between food materials and the lower teeth were directly measured. Masticatory pressure of five foods (white bread, raw carrot, cracker, rice cracker and Yokan) for fourteen healthy adults was measured, and the different pressure patterns related to the texture were discussed. Masticatory force versus time curves were characterized by each sample, although they varied largely by subject. Two peaks appeared in the masticatory curves of carrot and Yokan, more peaks were shown in cracker and rice cracker, but the first peak was missing for the bread mastication. The first peak corresponded to sample rupture, therefore the active pressure defined as the force divided by the contact area was found to reflect the breaking stress of the samples. Similar to the results of mechanical tests, brittle cracker and rice cracker showed a lower breaking force within a short time at the first peak. The last peak appearing just before teeth opening was similar to the maximum masticatory force for bread, cracker, rice cracker and Yokan, and did not correspond with the breaking force of samples. The order of the active pressure at the last peak was similar to that of stress values at very high strain measured in a compression test. The maximum force detected during one chew is not always measured in a normal instrumental test.
Kefiran production by Lactobacillus kefiranofaciens alone under the culture conditions established by mimicking the presence and activities of yeast cells in kefir grains was investigated. When the pH of the culture broth was controlled at pH 5.5 by adding a 4 N-NaOH solution during cultivation, cell growth and kefiran production were stimulated as compared with those in the cultivation without pH control. The addition of 5 g/l of yeast extract to the medium was essential for kefiran production. By sparging a mixed gas of N2 and CO2 at a volume ratio of 9:1 into the culture broth at 0.3 vvm throughout the cultivation, a slight increase in the amount (670 mg/l) of kefiran produced was observed as compared with that (650 mg/l) in the cultivation without aeration. When 10 g/l or 20 g/l of ethanol was added to the medium containing 50 g/l of lactose, the kefiran concentrations were about 930 mg/l or 840 mg/l at 8 days, respectively. The maximum concentration of kefiran obtained was about 1040 mg/l at 10 days, when 10 g/l of ethanol was added to the medium containing 75 g/l of lactose. These results showed that under the culture conditions established by mimicking the actions of yeast cells on L. kefiranofaciens in kefir grains the amount of kefiran produced was enhanced even when only the lactic acid bacterium was used.
W/O/W emulsions were prepared using low concentrations of emulsifiers in the oily and outer aqueous phases, and the formation of the emulsions were evaluated by the encapsulation efficiency of a fluorescent marker in the inner aqueous phase. W/O/W emulsions were produced even at low emulsifier concentrations, although the standard deviation of the encapsulation efficiency immediately after preparation became larger as the emulsifier concentration decreased. Long-term stability of the emulsions with no emulsifier was unsatisfactory, although emulsions with a lipophilic emulsifier only in the oily phase were stable for 30 days with a decrease in the encapsulation efficiency of less than around 5%. Emulsifier species also significantly affected the formation of W/O/W emulsions.
The proximate and functional properties of yam bean were determined in five-flour form as raw, boiled, fermented, roasted and malted. The functional properties determined were water absorption, fat absorption gelation, emulsion and foam capacities as well as foam stability. An improvement was observed in protein under all the processing conditions. Protein content ranged from 20.43% in raw flour to 23.63% in malted flour. Fermentation significantly (p<0.05) increased the fat content of the flour. The emulsifying and foaming capacities (50.7% and 40.20%, respectively) observed for raw flour were significantly higher than for the processed flours. Gelation was significantly (p<0.05) increased and decreased respectively, by fermentation and malting. The water absorption capacity ranged from 131.9% in raw flour to 218.8% in boiled flour. There was no significant (p>0.05) difference in the fat absorption capacity of the flours except the fermented flour (0.40 ml/g) which was significantly lower than the value (0.73 ml/g) obtained for boiled flour. Though a high foaming capacity was observed for raw flour, this was less stable compared with the processed flours. Yam bean flour was found to exhibit good functional properties and can offer a great potential in various food systems.
The relation between apparent molecular weight and physical properties of agar gel and sol were investigated. Agar was extracted from seven kinds of red seaweed, Gelidium, Pterocladia and Gracilaria, which were collected in different seas. The apparent weight-average molecular weight (AMw) and apparent molecular weight distribution of agar were measured by a high temperature type gel permeation chromatograph. Gel strength and melting point of agar gel, and the viscosity of agar sol were measured. The gel strength of agar gel from each seaweed increased with increasing AMw, and it was found that 3,6-anhydro-L-galactose and sulfate group affected gel formation. These results were also suggested by endothermic peaks of differential scanning calorimetry accompanying the gel-to-sol transition. The melting point of agar gel and the viscosity of its sol also increased with increasing AMw.
The effects of pH, the major food ingredients sodium chloride, sucrose, protein and organic acids on Escherichia coli inactivation by hydrostatic pressure treatment with the addition of allyl isothiocyanate (AIT) were investigated. E. coli JCM 1649 and CR-3, the latter of which was O157:H7, were increasingly inactivated by pressurization at pHs lower or higher than neutral. That is, both strains were completely inactivated by pressure treatment: JCM 1649 at 200 MPa and CR-3 at 300 MPa, at pH 4.5 or 8 when %80 μg/ml of AIT was added, although at other pHs they survived under the same pressure and AIT condition. Sucrose or protein decreased inactivation of E. coli JCM 1649 in pressure treatment combined with AIT, and the presence of 1% or more did not change the number of bacterial cells inactivated, regardless of the AIT concentration. The presence of 3% or more of sodium chloride also decreased inactivation but a lower concentration, i.e., 1% or so, enhanced the inactivation of the bacterium. Lowering pH by adding 0.01% of the organic acids succinic or malic acid was effective in combined treatment-induced inactivation. These findings suggested that some food ingredients, for example, a small amount of sodium chloride and organic acids, might enhance inactivation in pressure treatment combined with AIT, and that this combination was effective in practical application.
A total of 20 Vietnamese and Japanese rice varieties were evaluated for their main chemical components, physical properties, cooking quality, pasting properties, amylase activity, and instrumental measurements. Based on these quality evaluations, it was concluded that Vietnamese rice varieties are of the indica type which are characterized by having intermediate or high amylose content, high protein content and fat acidity, high water uptake ratio, expanded volume, and a cooked form texture which is high in hardness, low in stickiness, and has very low balance degree. Both Vietnamese and Japanese glutinous rice have similar characteristics of very high whiteness, low amylose content, low peak viscosity, and high stickiness. Japanese milled rice glossiness was greater than that of Vietnamese milled rice. In addition, Vietnamese rice had a lower “Mido” score than Japanese rice. In an instrumental test using a “Taste Analyzer,” both Vietnamese and Japanese rice gave a significantly high correlation with the chemical components in moisture and protein content measurements.
The browning reaction in barley products after boiling or steaming is undesirable in human food. We estimated the degree of browning reaction—the browning index (BI)—by the difference in the Hunter’s whiteness values of barley pastes before and after heat treatment (90\\xa1 C, 2 h). The apparent polyphenol content of barley flours, as determined by the Prussian blue method, was significantly correlated with BI in 42 barley varieties (r=0.766, p<0.001). Proanthocyanidin-free mutant lines showed very low BIs. Of the constituents of the crude polyphenol fraction, levels of prodelphinidin B3, procyanidin B3, an unidentified compound (‘compound C’) and (+)-catechin were correlated with BI (r=0.595, p<0.001; r=0.599, p<0.001; r=0.400, p<0.01; and r=0.384, p<0.05, respectively). These 4 constituents may influence the heat-induced browning reaction in barley products.
The essential oils from fresh and dried rhizomes of galanga (Alpinia officinarum Hance) were obtained by hydro-distillation, and fractionated to the hydrocarbon and oxygenated compound fractions by silica gel column chromatography. Twenty-eight hydrocarbons and 29 oxygenated compounds were identified by gas chromatographic (Kovat’s index) and mass spectrometric data. In the fresh rhizome, the main components (over 1.0% in content) were 1,8-cineole (50.0%), exo-2-hydroxy-1,8-cineole acetate (11.2%), β-caryophyllene (6.4%), α- and β-pinenes (1.7 and 2.6 %), β-bisabolene (2.6%), chavicol (2.0%), limonene (2.0%), 4-terpineol (1.6%), chavicol acetate (1.2%), and methyl eugenol (1.0%). On drying the rhizome, the monoterpene fraction (including hydrocarbon and oxygenated compounds) de-creased in content, and the sesquiterpene and aromatic compound fractions increased. Major components of the oil from dried rhizome (over 2.0% in content) were β-bisabolene (9.6%), 1,8-cineole (8.2%), chavicol acetate (5.9%), chavicol (5.3%), eugenyl acetate (3.7%), α-farnesene (3.3%), methyl eugenol (3.3%), β-caryophyllene (2.9%), α-bisabolol (2.6%), spathulenol (2.5%), farnesyl acetate (2.4%), 4-hydroxycinnamyl acetate (2.3%).
The methanol extract of the aerial part of Daucus carota var. sativus showed a stronger antioxidative activity than the standard synthetic antioxidant, 3-tert-butyl-4-hydroxyanisole (BHA). From this extract, five known compounds, luteolin 7-O-β-glucopyranoside (1), chrysoeriol 7-O-β-glucopyranoside (2), chlorogenic acid (3), maltol 3-O-β-glucopyranoside (4) and benzyl β-glucopyranoside (5) were isolated. Among them, when 1–4 were investigated for their antioxidative activity using the ferric thiocyanate method, 1–3 indicated an antioxidative activity. The scavenging effect of 1–4 on the stable free radical, 1,1-diphenyl-2-picrylhydrazyl was also examined. Compounds 1 and 3 showed a scavenging effect. In addition, 1–3 were assayed for their inhibitory effects on the activation of inactive hyaluronidase induced by compound 48/80. All tested compounds showed this effect.
This study focused our attention on the changes in physiological activities of cabbage after treatment under various cooking conditions. Fresh, boiled, broiled and acid-treated cabbage juices and solutions after cooking were examined for their priming effects of the endogenous production of tumor necrosis factor (TNF-α) in mice, the induction of quinone reductase [NAD(P)H: (quinone-acceptor) oxidoreductase, EC220.127.116.11: QR] in Hepa 1c1c7 cells, and the anti-proliferative activities on Hepa 1c1c7 cells. Boiled and broiled cabbage juices as well as fresh juice significantly increased the production of TNF-α and raised the potency of QR induction activities. Acid-treated cabbage juice was little effective in enhancing the productivity of TNF-α or the induction of QR. The growth of Hepa 1c1c7 cells was inhibited by fresh and broiled cabbage juices.
To estimate the antigenicities of collagenase-treated gelatins, we assessed some antibodies to porcine skin gelatin from a human immortalized B-cell library. A competitive enzyme-linked immunosorbent assay showed that bindings of two antibodies to porcine skin gelatin were strongly inhibited by intact gelatin, but were not inhibited by collagenase-treated gelatins. We concluded that those antibodies secreted by immortalized human B cells could be useful to estimate the antigenicity of the collagenase-treated gelatins.