This paper discusses recent advances in cereal drying. It focuses on mathematical modeling of convective heat and mass transfer using air as the drying medium. The mathematical modeling of air distribution follows conservation of momentum and a constituent equation relatinng the velocity of air to its static pressure. The paper presents data obtained from a series of detailed wheat drying experiments. It is shown that the existing simulation models can be improved once the thin layer drying equation is updated spatially and temporally within the bulk grain. The use of variable properties in calculating transient moisture contents and temperatures also improves the accuracy of mathematical simulations.
Sucrose fatty acid esters were used as coating materials to observe their effects on the ripening of ethylene-treated cavendish bananas. Bananas were coated with 2% sucrose fatty acid esters namely sucrose lauric, palmitic and stearic acid esters after 100 ppm ethylene application for 12 h and stored at 20°C. The sucrose fatty acid ester coating reduced the weight loss and extended the storage life of the bananas. Coated bananas reached close to the hue angle of 90 degrees later than non-coated bananas, i.e., delayed degreening. Non-coated bananas which ripened faster also lost their firmness earlier. Among the sucrose fatty acid esters, a 2% palmitic acid ester coating significantly delayed the ripening phenomenon of bananas. The reducing sugar content of 2% stearic acid ester-coated banana was 7.56 g/100 g and was found to be significantly higher than that of other treatments. Test panel members chose 2% lauric acid ester-coated bananas with respect to taste, sweetness and hardness.
The MAILPROF computer program for constant ambient temperatures (C-Model) was generalized to accept varying ambient temperatures (V-Model) by implementing the solution of the appropriate differential equation. The time-temperature profiles of gutted salmon with frozen gel pads or flake ice (3:1 ratio by mass) inside a thermally insulated (expanded polystyrene) box at varying ambient temperatures were predicted and compared with the measured temperatures. The predicted fish temperatures (V-Model) correlated well with the measured fish temperatures when fish and frozen gel pads were used and no significant differences (p>0.05) were observed between the two. The V-Model can be used to predict the quantity of cooling gel or ice needed to keep the fish below 8°C in transport at constant and varying ambient temperatures. The time-temperature profiles of smoked salmon packaged with cooling gel were measured in mail transit by miniature data loggers and also predicted by the C and V-Models. No significant differences (p>0.05) were found between the measured and predicted (V-Model) fish temperatures.
Our attention was focused on the factors influencing the drying characteristics of wet porous materials in consideration of the sample structure and the radiative heat source. By selecting three kinds of membrane filters, we examined the effects of the mean pore diameter, the irradiation power and its spectral distribution as variables using a far-infrared (FIR) heater and a near-infrared (NIR) heater. As a result, the drying characteristics were influenced by the mean pore diameter, and the FIR drying rate was faster than the NIR drying rate. In addition, we examined the relationship between the drying characteristics and the apparent optical properties of the drying sample. Consequently the results suggested that the diffuse reflectance of the membrane filter obtained in the present experiments was applicable to analyze the infrared drying characteristics. Moreover, we deliberated that it was possible to simulate the infrared drying characteristics by understanding the optical properties.
The relative activity of lysozyme by high pressure treatment over the pressure range of 50-300 MPa for 10 min at 0, 35 and 60°C was investigated. The activity gradually decreased by treatment at more than 200 MPa at 60°C, though stable at 0 or 35°C. To obtain a lysozyme with high activity, the lysozyme-dextran complex was prepared from a premixed solution of lysozyme and dextran, which was exposed to high pressure. The lysozyme-dextran complex showing the highest activity was prepared by the high pressure condition of 150 MPa for 60 min at 60°C in the weight ratio of 1:5 (lysozyme:dextran). It was concluded that the enhancement of the lysozyme activity of the lysozyme-dextran complex was due to the combination of lysozyme and dextran that was a hydrophilic polysaccharide.
Chungkuk-jang (hereafter referred to simply as jang), a traditional fermented soybean product in Korea, is manufactured by a process similar to that of Japanese itohiki-natto (referred to as natto). The bacteria isolated from jang were identified to belong to Bacillus subtilis (Ehrenberg) Cohn. The quality of jang manufactured with the isolated bacteria and two kinds of natto bacilli, B. subtilis (natto) KFP2 and KFP419, was evaluated to be as good in sensory evaluation except for the viscosity. Therefore, the isolated bacteria were estimated as B. subtilis (natto). In jang, soybean proteins were degraded to increase soluble and formol nitrogens. Sticky materials were produced, and natto-like flavor was emitted. Jang prepared in the laboratory showed elastase activity, and it was twice-to-three-times higher than that of the commercial product. While jang is a different product from that of natto, both products contain the common starter and elastase.
Changes in carotenoids and their fatty acid esters in banana peel during ripening were investigated using a combination of an alumina column and high-performance liquid chromatography (HPLC). The level of total carotenoids decreased during the early stage of ripening but recovered again to the level of green fruit. Carotenoids belonging to both the α- and β-carotene categories decreased in the early stage of ripening, then the α-carotene category, especially lutein, increased significantly, but not the β-carotene category. Because the amount of α-cryptoxanthin was quite small, the process of hydroxylation of α-carotene to lutein, where α-cryptoxanthin was the intermediate product, seemed to occur quickly. Free lutein was easily esterified to lutein monoester and then was gradually further esterified to lutein diester; the amount of free, monoester and diester of lutein was about 20, 60 and 20% of total lutein, respectively after 4 days' storage. A small amount of isolutein, which is an epoxy of lutein, was observed and all isolutein was in the monoester form after 4 days' storage, but no diester form was detected.
Duck eggs treated with 1.0 N HCl up to 120 min to adjust the permeability of the shell were immersed in 26% NaCl (0-40 days) and subsequently heated at 85°C for 90 min to obtain the salted eggs in order to investigate the effect of NaCl on the granulation and oil-off of the yolk formed. During brining, the NaCl contents of the yolk and albumen were increased 2-10 fold due to HCl treatment of the shell. The oil-off ratio, defined as the ratio of the free lipid to the lipid content of the yolk, was also affected by the penetration rate and brining time. Eggs treated with 1.0 N HCl for 120 min showed reduced time required to achieve the maximum lipid content and oil-off ratio and had a lower maximum value of oil-off ratio than eggs treated with 1 N HCl for 0-80 min. The yolk of HCl-treated (1.0 N, 80 min) egg changed in appearance mealy form to be granulous at 5-10 days and to a soft gel at 15-20 days after brining. In comparison, the eggs without HCl treatment respectively required 20-25 and 40 days for these changes. This study suggests that sustained brining may result in the formation of a gel-state yolk, and the NaCl penetration rate affects only the time for the change in forms.
Acylated κ-casein (kCN) and β-casein (βCN) were used (0.1% w/v) to improve textural and flavor properties of nonfat/low calorie yogurt and lowfat ice cream. Acylation was achieved by base-catalyzed ester exchange of N-hydroxysuccinimide esters of naturally occurring caprylic (C:8), lauric (C:12), and palmitic (C:16) acids. The degree of modification of the proteins was controlled by adjusting the ratio of fatty acid to protein (1:1 and 2:1). The hydrocarbon chain length was referred to as the “length.” Products with the acylated proteins displayed significantly improved texture. Shorter length (C:8) had the best effect. In terms of flavor, longer length provided better improvement of flavor ratings. Stability as assessed by degree of syneresis and gel strength was markedly improved by all acylated proteins and this was particularly true when acylated βCN was used. The apparent viscosity of the product was better improved by acylated kCN. Data indicated that acylated proteins markedly improved product quality.
This study was conducted to investigate the effect of five amino acids, aspartic acid, glutamic acid, histidine, cysteine and phenylalanine, and of two dipeptides, anserine and carnosine, on the uptake and transport of iron across monolayers of Caco-2 cells. Caco-2 cells were grown on polycarbonate membrane inserts in serum-free medium [DMEM plus ITS (5 mg/l insulin, 5 mg/l transferrin and 5 μg/l selenious acid)]. The anserine, carnosine, glutamic acid, histidine and aspartic acid, except for cysteine and phenylalanine, at 20 μM significantly increased the uptake and transport of iron. Iron uptake and rate of iron transport in the presence of aspartic acid at 20 μM were significantly greater than those of other test solutions. When the concentration of added carnosine, anserine, glutamic acid, histidine and phenylalanine was increased from 20 μM to 1 mM in the test solution, the uptake and transport of iron was further increased. The results of the present study indicated that aspartic acid, glutamic acid, histidine, and the dipeptides, anserine and carnosine, enhanced the uptake and transport of iron by Caco-2 cells.
Six aromatic compounds, asebogenin (1), 2',6'-dihydroxy-4'-methoxydihydrochalcone (2), 3-geranyl-4-methoxy-benzoic acid (3), 3-geranyl-4-hydroxybenzoic acid (4), nervogenic acid (5) and 2,2-dimethyl-6-carboxyl-8-prenyl-chromene (6) were isolated from the methanol extract of the aerial part of Piper elongatum VAHL., whose leaves are used as a folk medicine in South America. The structures of 1-6 were elucidated by MS, 1H-NMR and 13C-NMR spectroscopies, and chemical evidence. Among these compounds, 1 showed stronger antioxidative activity than that of α-tocopherol, and 4 and 5 exhibited higher activity than that of t-butyl-4-hydroxyanisole (BHA) using the ferric thiocyanate method.
The proteolysis degree in ewes' milk by 5 Streptococcus thermophilus and 4 Lactobacillus delbrueckii subsp. bulgaricus strains, as well as by their 20 combinations in ewes' milk yoghurt, was determined. Samples for analysis were taken after 24 h and 5 days' storage at 4°C. Determination of proteolysis degree in the 2% and 12% TCA soluble fractions was performed by the photometric ninhydrin method. The proteolysis degree varied among the single strains and their combinations. The proteolytic activity of Lb. bulgaricus strains was greater than or at the same level as the activity determined for Str. thermophilus strains. In yoghurt, the proteolysis determined was higher than that of the single strains. Changes in the proteolysis degree were also observed between the 24-h and 5-day samples. The highest total amount of free amino acids/peptides soluble in the 2% and 12% TCA fraction, in the 24-h as well as in the 5-day samples, was produced by Str. thermophilus strain CNRZ 404, Lb. bulgaricus strain CNRZ 1159 and the combinations CNRZ 1198/CNRZ 1159, ACA-DC 116/CNRZ 1159.
A rapid and precise method for the simultaneous determination of glutathione (GSH), γ-glutamylcysteine and cysteine in commercial GSH-enriched yeast extract (GSH-YE) is described. Isocratic separation of the above compounds was performed using an aminopropyl silica column. Post-column derivatization with N-acridinylmaleimide (NAM) was performed followed by fluorimetric detection. This HPLC method could be applied for the determination of GSH, γ-glutamylcysteine and cysteine in commercial yeast extract. All of the commercial GSH-YE contained γ-glutamylcysteine (0.057-0.50 g/100 g) and cysteine (0.020-1.71 g/100 g).
The inhibitory peptides of angiotensin I-converting enzyme have been identified from cottonseed proteins. The inhibitory peptides in the pepsin hydrolyzate of cottonseed globulin were purified by successive chromatographies on CM-Sephadex C-50, Sephadex LH-20, and reversed phase high performance liquid chromatography using a C18 column. The amino acid sequences of inhibitory peptides were Tyr-Arg-Lys-Ile-Arg-Ser-Gln-Leu and Trp-Gln-His-Gln-Ser-Arg-Gly-Arg-Phe. The IC50 value of the former peptide was 3.8 μM and the latter was 27 μM.
The antimicrobial activities of extracts from the leaves and rhizomes of Sachaline giant knotweed, Polygonum sachalinense, were examined. Of all the fractions separated using various solvents from the methanol extracts, the ethyl acetate fractions obtained from both the leaves and rhizomes had the highest antibacterial activity. Chloroform-separated fractions obtained from the rhizomes also displayed high antibacterial activity against some bacterial strains. Ethyl acetate-soluble fractions obtained from both the leaves and rhizomes showed effective growth inhibition against Bacillus brevis, Bacillus cereus, Bacillus coagulans, Curtobacterium flaccumfaciens, Staphylococcus aureus, Aeromonas hydrophila and Pseudomonas fluorescens.