Attempts to find a solution to the problem of beer staling have been unremitting: hundreds of articles have been published during the last few years alone. This paper introduces recent developments in brewing science and discusses basic research into the formation of stale flavors, together with measures proposed and adopted to counter them. Included are advances made both in brewing technology and beer distribution systems, which help minimize staling, with an example of product temperature management used by a Japanese company.
Lowfat Cheddar cheese (5% fat) was manufactured using different commercial fat replacers and aged for 6 months at 5°C with objective to study rheology and microstructure. Two protein-based fat replacers, Dairy Lo (DL) and Simplesse (SIMP), one protein-based fat-like perception enhancer termed “Fat-like Perception Enhancer” (FLPE) (also termed LiPro elsewhere), and two carbohydrate based fat replacers, Novagel (NOV) and Stellar (STEL), were used for the study. Rheological properties were determined using an Instron Universal Testing Machine. Lowfat control (LFC) cheese had significantly higher stress values indicating a hard rubbery texture compared to full fat control (FFC). Fat replacers decreased cheese stress values in the order; FFC<FLPE<STEL<DL<SIMP<NOV< and LFC. In terms of strain values, LFC had the lowest strain value indicating “crumbliness.” Considering that FFC had an ideal strain value, FLPE was the closest followed by DL and STEL. Scanning electron microscopy was carried out to observe cheese ultrastructutre. The FFC cheese had a spongy appearance due to globular cavities created in the cheese matrix by butterfat. These cavities were smaller in NOV and STEL than the rest. In general, fat replacers improved the textural quality of lowfat Cheddar cheese.
The properties of protein adsorption and desorption of alumina ceramic membranes were investigated using several types of proteins. The effect of pH on the protein adsorption was studied by soaking the membrane in protein solution. For basic proteins, the amount of protein adsorbed increased at pHs lower than the isoelectric point due to an electrostatic interaction between the protein and the membrane. A single protein solution was filtered and the protein was adsorbed on the membrane. Most of the adsorbed protein was desorbed and concentrated by changing the ionic strength or pH of the filtered solvent, however, the protein remaining on the membrane was not washed out even by soaking in sodium lauryl sulfate (SDS) solution. The adsorption-desorption experiments were carried out using a binary protein solution of lysozyme and β-galactosidase of pH 3 for the adsorption step and phosphate buffer solution of pH 7 for the desorption step. During the adsorption step, β-galactosidase was adsorbed more than the lysozyme, however, the absolute adsorbed amount was smaller than that in the single protein solution of β-galactosidase since the adsorption site was partially occupied by lysozyme. β-Galactosidase was concentrated seven-fold in the permeate during the desorption step in the first 20 s, while the concentration of lysozyme was one-tenth of its original value.
Relationship between the quality of shrimp cracker and the water activity (Aw) was studied by means of a sensory test. Crispness, odor, taste, and total acceptability decreased with the increase in water activity. Critical water activity, defined as a point where total acceptability became negative, was 0.35 Aw. Multiple regression analysis showed that crispness had great responsibility for total acceptability. Apparent breaking strength and breaking energy obtained by instrumental analysis increased with the increase in water activity within the range of 0 to 0.52 Aw. The relationship between the logarithmic value of breaking strength and the intensity of crispness indicated that the analysis of the breaking strength was a useful tool for quality evaluation of the shrimp cracker.
Fish meat emulsion was prepared from very-low-lipid sardine minced meat obtained through grinding or suspending in weak alkaline solution, and the effect of the yolk/white ratio in a blended emulsifier on this emulsion was investigated using rheometry and microscopy. A blended egg yolk/egg white ratio of 0.233/0.466 was equal to a constituent ratio in the real whole egg. Four changes in flow property, reported when whole egg was used as an emulsifier instead of egg yolk, were reproduced in ground-meat emulsion with a blended emulsifier: (1) the decrease in the flow behavior index in the up-curve (2) the increase in the yield stress in the up-curve (3) the decrease in the consistency index in the down-curve and (4) the increase in the hysteresis loop area. In suspended-meat emulsion, (2) and (4) became obviously true at the yolk/white ratios of 0.1/0.6 and 0.0/0.7. Lower moisture in suspended meat, which was prepared from sardines chilled in ice-water for a slightly longer period, would be the main reason for the result that these two items were not reproduced at the ratio of 0.233/0.466. The effect of the egg-white portion worked well under the higher moisture conditions of the suspended meat due to more egg-white. The increase in oil droplet size by the effects of both yolk and white caused the deformation of the droplet shape and the resulting coalescence during the shear. As a result, the shear-thinning property was intensified. The thread-like substances and the myofibrillar network structure tightly adhered to the surface of the droplet during the shear and promoted the coalescence at the yolk/white ratio of 0.0/0.7.
The effect of hydrostatic pressure sterilization was investigated in tomato juice. Saccharomyces bailii and Bacillus coagulans were used as the test microorganisms added to the tomato juice. The logarithm of the time of hydrostatic pressure treatment and the logarithm of the fungicidal effect of S. bailii were directly proportional at 200 MPa, after the number of viable fungi did not change for a few minutes (at 200 MPa). When the NaCl content in tomato juice was 3% or more, the effect of NaCl on the survival of S.bailii at 200 MPa was recognized. The time before the number of viable fungi began to decrease was prolonged, and the rate of extinction was slower than with a NaCl content of 1% or less in tomato juice. In the case of the survival of B. coagulans at 400 MPa, the same result was indicated.
Unboiled Japanese buckwheat noodle “Nihon-soba” is a perishable product when stored at room temperature. In order to find effective food additives for the quality preservation of this noodle, commercial food additive A-N was tested, together with lactic acid. A-N was a mixed compound of lysozyme 23.7%, glycine 49.8%, fumalic acid 17.5%, sodium caseinate 1.5%, and glycerol-fatty acid ester 7.5%. Although no inhibitory effect on microbial growth was observed at 0.2% lactic acid, and the control 0.5% A-N and the mixed use of 0.5% A-N and 0.2% lactic acid showed inhibitory effects on microbial growth. This combination use of 0.2% lactic acid and 0.5% A-N had clearly much more inhibitory effect than their individual effects. In semi-dried samples, 0.5% A-N and 0.2% lactic acid, as well as their combination uses, appeared to have considerable effect on maintaining the quality of the buckwheat noodles compared with the control.
Water sorption isotherms at 298 K for six kinds of fresh vegetables (carrot, daikon (Japanese radish), eggplant, potato, pumpkin and sweet-potato) were measured using a static equilibration method over saturated salt solutions in the relative humidity range from 11.3 to 97.3%. The equilibrium moisture content data were fitted to a modified Dubinin-Astakhov (DA) equation that assumes a Weibull probability density function to the desorption probability under the adsorption potential change. The modified DA equation was confirmed to be very accurate in predicting the water sorption isotherms of the vegetables. In addition, the test vegetables could be classified into two groups by the n (one of the DA parameters) values, which denote the porous degree of the adsorbent. One group consisted of carrot, eggplant and pumpkin. Daikon, potato and sweet potato belonged to the other group.
Listeria monocytogenes were isolated in 5 lots, more than one cell in each 25-g sample of 10 lots of chicken meat, which was obtained from several different areas in Japan. From taxonomic study, the psychrotrophic type of 3 isolates grew well at 4°C on Trypticase soy agar slant, whereas 2 isolates grew poorly. Cells of all isolates were sensitive to γ-irradiation in phosphate buffer, and the D10 values obtained were 0.16 to 0.18 kGy under aerobic irradiation conditions similar to the values of salmonellae. In the chicken meat sample, the D10 value obtained was 0.42 kGy the same value as in phosphate buffer under anaerobic irradiation conditions, and the necessary dose for inactivation of L. monocytogenes was estimated to be 2 kGy in raw chicken meat below 10-4 CFU (colony forming unit) per gram. In the storage study of chicken meat which was inoculated with about 3×103 CFU per gram of L. monocytogenes, the psychrotrophic type of the isolates grew quickly at 7 to 10°C storage. However, a dose of 1 kGy was also effective to suppress the growth of L. monocytogenes at refrigeration temperatures below 10°C.
Paprika extract (50 to 100 μg/ml) obtained by suspending ground paprika seeds in water, adding ethanol (50%, v/v), and then filtering the suspension, inhibited the growth of film-forming yeasts (Kloeckera, Pichia, Debaryomyces, and Candida species) isolated during the production of ume-zuke, a processed food product made by salting Japanese apricots (Prunus mume). The antimicrobial activity of the extract towards Pichia anomala was influenced by the initial number of yeast cells, as well as the temperature, pH, and sodium chloride concentration of the culture medium (ume vinegar). The inhibitory effect was cumulatively enhanced, although not synergistically, when the paprika seed extract was used in combination with either SO2, sorbic acid, thiamine dilauryl sulfate, or acetic acid. The antimicrobial activity of the extract was not influenced by the vinegar components. The extract proved to be very effective as a preservative to prevent the contamination and spoilage of ume-zuke by film-forming yeasts.
The effect of experimental diets with calcium tofu containing casein phosphopeptides (CPP) on ovariectomy (OVX)-induced bone loss was investigated. Experimental diets containing either calcium tofu (100 mg Ca), calcium tofu containing 28 mg CPP (CPP tofu) or calcium tofu containing 28 mg dephospho CPP (dephospho CPP tofu) were freely given to sham-operated rats or OVX rats for 4 weeks. OVX caused a significant decrease in the length, dry weight and mineral density of femur. Calcium content in the femoral diaphysis and epiphysis was significantly decreased by OVX. These decreases were completely prevented by the feeding of diets with CPP tofu. Such preventive effect was not seen by the feeding of diets with dephospho CPP tofu. These results demonstrate that the diets with calcium tofu containing CPP have a preventive effect on OVX-induced bone loss due to enhancing calcium availability.
The effects of salts and pH on the emulsion stabilities of water/kerosene (1:1, w/w) emulsions prepared with digalactosylmonoacylglycerol (DGMG) and trigalactosylmonoacylglycerol (TGMG) were investigated. The creaming stabilities of the emulsions prepared with 0.05% DGMG and TGMG did not change up to 0.2 M CaCl2, and their medium droplet sizes were constant. The creaming stabilities of their emulsions with salts were higher, and the medium droplet sizes of their emulsions were smaller than those of the sucrose esters of fatty acids and lysolecithin. The ratio of the oil phase weight to total weight separated by centrifuging the DGMG and TGMG emulsions were constant up to 0.2 M CaCl2, and were smaller than those of the sucrose esters of fatty acids and lysolecithin. The creaming stabilities of the emulsions prepared with 0.05% DGMG and TGMG did not change with various pHs, and their medium droplet sizes were constant. The creaming stabilities of their emulsions in an acidic pH were higher than those of the sucrose esters of fatty acids. The oil phase separation by centrifuging the DGMG and TGMG emulsions were constant at various pHs.
Digalactosyldiacylglycerol (DGDG) and trigalactosyldiacylglycerol (TGDG) were extracted from pumpkin and then hydrolyzed to the corresponding monoacylglycerols by 1,3-specific lipase from Rhizopus arrhizus. The hydrolyzates from DGDG and TGDG were identified as digalactosylmonoacylglycerol (DGMG) and trigalactosyl-monoacylglycerol (TGMG) by TLC analysis, acid hydrolysis and GC analysis, respectively. The surface tensions of the aqueous DGMG and TGMG solutions significantly decreased up to 0.005% DGMG and TGMG, and then decreased slightly at more than that concentration. The foamabilities increased with the DGMG and TGMG contents. The foamabilities and the foaming stabilities of DGMG and TGMG were superior to those of the other commercial emulsifiers. The interfacial tensions at the water/kerosene interface of DGMG and TGMG significantly decreased up to 0.001% DGMG and TGMG, and then slightly decreased at more than that concentration. The types of water/kerosene (1:1, w/w) emulsions prepared with DGMG and TGMG were O/W, respectively. The creaming stabilities and the strength of the interfacial film of the emulsions increased with the DGMG and TGMG contents. The emulsifying properties of the DGMG and TGMG emulsions were almost equal to those of the commercial emulsifiers.
In order to invesigate another function such as food in Morokheiya, the angiotensin-converting enzyme (ACE) inhibitor was extracted with 80% ethanol from the leaves of Morokheiya (Corchorus olitorious). The extract was dried, dissolved in water, defatted with ether and decolored with activated carbon. The ACE inhibitor was purified by successive ion-exchange chromatography, Amberlite IR-120B, Dowex 50W-X8 and Dowex 1-X4, respectively. The ACE inhibitor was further purified by silica gel column chromatography and finally purified and isolated by high performance liquid chromatography (HPLC) on Asahipak NH2P-50. The ACE inhibitor showed a positive ninhydrin reaction and no significant absorbance. The present ACE inhibitor was identified as Nicotianamine based on the comparative study using amino acid analyzer, TLC and capillary electrophoresis.