The use of chemically modified starches to improve the physical properties of non-fat stirred yoghurt was investigated. Yoghurts were prepared from non-fat milk powder, sucrose, water and tapioca starch acetates (TSA-1, TSA-2, TSA-3), tapioca distarch phosphates (TDP-1, TDP-2, TDP-3) or native tapioca starch at 1% (w/w). Syneresis, particle size distribution and viscoelastic properties of the yoghurts were determined, and flow behaviour was described using the Herschel-Bulkley model. Furthermore, interactions between milk proteins and modified starches attributed to protein surface hydrophobicity were characterized. Results showed that yoghurts with starch acetates exhibited higher yield stress, consistency coefficient (K) values, hysteresis loop area, storage modulus (G′) and loss modulus (G″). Protein surface hydrophobicity was significantly influenced by the addition of starch acetates, and TSA-3 yoghurt exhibited the lowest values. This study concluded that the addition of TSA-3 starch showed better results in terms of the rheological properties of non-fat yoghurt.
The effect of fish oil supplementation on the quality of frozen and unfrozen sasa-kamaboko was evaluated. Alaska pollock surimi was emulsified with 0% (control), 2.5%, or 5% fish oil, and after shaping and heating, the resultant sasa-kamaboko samples were stored at −20 °C for 2 or 4 weeks. Compared to the control, emulsification of fish oil into sasa-kamaboko was found to significantly (p < 0.05) improve the water-holding capacity, whiteness, and breaking strength before freezing and after frozen storage. Microscopic observation revealed that the fish oil particles were well distributed even after frozen storage, and there was only slight structural damage. It was indicated that fish oil supplementation affected the formation and distribution of ice crystals, which had positive effects on the quality of thawed sasa-kamaboko. Our findings may be used to improve the manufacture process of high-quality, frozen surimi-based products.
During sardine fish sauce production, salt concentration needs to be maintained at a specific level to inhibit the growth of undesirable microorganisms. Here, we employed pressurized CO2 to control microbial growth in fish sauce. Fish sauces prepared at 30 °C for 6 months under 1–5 MPa pressurized CO2 with 10% NaCl (FSCO2) were compared to those produced under atmospheric pressure with 10–20% NaCl (FScon). FScon with 20% NaCl had a slight putrefied odor, whereas FSCO2 exhibited a favorable odor despite its low NaCl concentration. In FSCO2, bacterial count, biological amine content, and pungent organic acids decreased while free amino acid content increased compared to the control. Sensory evaluation indicated the FSCO2 had weaker rancidity, fish-like, putrefactive, and pungent odors but an enriched dashi-like odor. These results show that pressurized CO2 application can produce a salt-reduced, amino acid-enriched, and sensorially ameliorated sardine fish sauce.
Frozen Alaska pollock surimi (FA, A, and RA grades) was used to clarify how the heating method (ohmic heating and water bath heating) and heating rate affect the physical properties of heat-induced gels. Textural properties were significantly influenced by the heating method and heating rate. In 1-step heating, slow heating enhanced the gel strength of high-grade surimi more effectively than that of low-grade surimi. The quality of gels prepared by water bath and ohmic heating differed even if the heating time to the final temperature was the same, probably due to differences in the linear and non-linear temperature patterns of the two heating methods. The results of gels formed by 2-step heating and those with suppressed setting by EDTA confirmed that a slow heating rate enhanced gel strength by altering the setting phenomenon, but was also influenced by the modori effect, and the degree of enhancement differed depending on the surimi grade.
The relationship between soft wheat flour characteristics and sugar snap cookie (SSC) quality was analyzed using SSC diameter (SSCD) as an indicator of SSC quality. Various flour streams (flours), obtained by milling four kinds of soft wheat (Western White and three Japanese domestic wheats) with different characteristics, were used. The results showed that the soft wheat flour characteristics that greatly affected SSCD were damaged starch (DSC), amylose (AC) and protein contents (PC). SSCD showed a significantly higher correlation with DSC than AC and PC; the correlation coefficients were −0.938, 0.644 and −0.552, respectively. Based on the results, stepwise multiple regression analyses were performed, and a multiple regression model with DSC, AC and PC as explanatory variables was obtained. The model can be used to accurately estimate SSCD (corrected R2 = 0.915, standard error of residual = 2.22 (mm)). This model was effective as a means to estimate the SSC quality of various weak flours easily and accurately.
General qualities (moisture, grain size and quality level), cooking qualities (grain elongation), sensory evaluation and judgment of fungi, using Phka Rumduol and Somali collected from three markets in Takeo Province, Phnom Penh City and Battambang Province were determined. Rice qualities and grade of the two varieties among three markets in each of the three locations were rather stable. On the other hand, those among the three locations were not always stable. Grain size and grain grade were generally higher in the rice from Battambang Province. Grain size before and after cooking had almost similar tendencies. Rice qualities between the two varieties showed a tendency for Phka Rumduol to be longer than Somali in grain length, while Somali was wider and heavier than Phka Rumduol in grain width and weight. Sensory evaluation by local panelists showed that all cooked rice was highly evaluated in grain dimension, whiteness, hardness, aroma and favorability. No fungi were detected in any of the rice samples. The overall results of this experiment showed two rice varieties collected in three markets in three locations in Cambodia were generally and permissively high in quality both for domestic uses and exportation.
There are many sugar products in foods, and it is desirable to satisfy both product quality and process operability. One example of a sugar product is fondant with crystalline material containing xylitol, and it is difficult to formulate products with desired qualities such as crystallinity. The production process of crystalline material can be regarded as melt crystallization. The objective of this study was to investigate the relationship between the condition of melt before depositing process and the crystallization phenomena for xylitol-sorbitol system. The results showed that the crystallization process after depositing was affected by the initial slurry density. The Avrami equation was applied to this system to analyze the mechanism of melt crystallization. It was confirmed that the crystallization process can be analyzed and crystallinity can be predicted by the Avrami equation. Melt with high slurry density and high temperature is preferable for formulation of desired crystal qualities.
Lipid oxidation progress in semi-dried shrimp (Acetes chinesis) products during cold storage was studied. Samples with low salt content and without vacuum package exhibited the highest level of lipid oxidation and browning development. High salt content samples showed lower TBARS and 1-penten-3-ol concentration during whole storage period than low salt samples. Vacuum package showed some effects in retarding lipid oxidation particularly for low salt content sample. Vacuum package could also preserve astaxanthin at the end of storage. Browning development in this semi-dried shrimp product during storage was not due to astaxanthin loss. The mechanism of the browning requires further investigation.
The aim of this study was to evaluate the bactericidal effects of coffee and chlorogenic acid (CQA) on Escherichia coli and Salmonella spp. under low pH conditions simulating gastric juice. E. coli and Salmonella sp. survived at pH 1.5 and pH 3.0, respectively, for 3 h at 37 °C in our experimental conditions. However, 1.0% soluble coffee and 0.5% CQA killed E. coli at pH 1.5, and Salmonella spp. at pH 3.0, respectively. Thus, coffee and CQA showed bactericidal activity under low pH conditions. Although CQA showed stronger bactericidal activity than coffee, considering the content of CQA in soluble coffee, the bactericidal effect of soluble coffee could not be only attributed to CQA. The ethyl acetate fraction prepared from soluble coffee showed the highest activity. As this fraction contained various phenolics as well as CQA, these phenolics may be effective in killing the bacteria under low pH conditions.
The crude enzyme of latex from Japanese milkweed (Metaplexis japonica) clotted 10% reconstituted skim milk, and the curd was stable with no visible collapse. Additionally, milk-clotting properties of the crude enzyme were investigated. Multiple proteases were suggested to be involved in milk clotting, and cysteine proteases played a major role. The crude enzyme showed a higher milk clotting activity under acidic conditions and at 60 °C when a reconstituted low-heat skim milk ranging from pH 5.5 to 8.0 and from 25 to 60 °C was used as a substrate, respectively. Finally, the casein hydrolysis pattern of the crude enzyme showed a similar pattern to microbial rennet (degradation primarily of κ-casein).
The optimization of fermentation medium for α-galactosidase production by Trametes versicolor was investigated by using orthogonal design in shaker flask fermentation. The optimal liquid medium for α-galactosidase production by T. versicolor was consist of 1.0% soybean cake power, 0.60% galactose, 0.15% KH2PO4, 0.09% MgSO4. Then, the α-galactosidase from T. versicolor (TVG) was purified and characterized. The purified enzyme, a monomeric protein with a molecular weight of 70 kDa, was purified 332-fold by means of ion exchange chromatography and gel filtration. The optimal pH and temperature of TVG with p-nitro-phenyl α-D-galactopyranoside (pNPG) as substrate were 3.0 and 60 °C, respectively. The activity of TVG was inhibited by N-bromosuccinimide (NBS), constituting evidence for the essentiality of tryptophan residue(s) at or in the vicinity of the active centre. The α-galactosidase presented a broad substrate specificity, which included pNPG, melibiose, raffinose, and stachyose with Km values of 0.651, 3.66, 15.1, and 4.47 mM, correspondingly. Galactose acted as a noncompetitive inhibitor with Ki and Kis of 2.88 and 0.132 mM, respectively. A synergistic acceleration in guar gum degradation was found when TVG and mannanase were combined.
The quality attributes and cell wall materials of ‘Suli’ plums stored at 4 °C and 25 °C with 80%–90% relative humidity were investigated. Rapid changes in firmness, soluble solids content (SSC), titratable acidity (TA), and decay rate at 25 °C were evaluated. These changes were suppressed in the plums stored at 4 °C. Modification of cell walls in the ‘Suli’ plums was investigated by Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). FTIR and AFM indicated that low temperature significantly maintained cell wall integrity, as well as suppressed the conversion of protopectin and degradation of pectin during storage. The results confirmed that the microstructures and composition of the cell wall in ‘Suli’ plums were closely related to firmness, which is considered the main index of fruit softening.
The size of emulsion droplets can influence the taste and texture of food. Therefore, we investigated the effect of droplet diameter of oil-in-water (O/W) emulsions on the aroma release rate from emulsions. O/W emulsions were prepared to droplet sizes of 0.4, 2.0 and 20 µm. The release rates for seven aroma compounds, viz., limonene, ethyl hexanoate, 2-methylpyrazine, benzaldehyde, ethyl benzoate, α-terpineol, and benzyl alcohol, from the O/W emulsions were measured under non-equilibrium. The aroma release rate of 0.4-µm droplets was higher than that of 2.0- and 20-µm emulsion droplets irrespective of their partition coefficients. Aroma compounds in small oil droplets can rapidly diffuse in the water and air phases because a small droplet has a large oil–water surface area. Overall, our findings suggest that small droplet emulsions can be used to release more aroma compounds than large droplet emulsions without changing the emulsion components.
Zein is a major by-product of corn processing and has a wide range of applications in many fields due to its unique solubility and specific amino acid composition. The aim of this study is to hydrolyze zein stepwise using alcalase and proteinase K while considering the enzymatic hydrolysis sequence and assessing the zein-chelating ability, solubility, foaming, and emulsification properties of the zein hydrolysate. The antioxidant activity of Zn2+ chelating peptide was determined. Zinc-chelating ability was used as the evaluation index, and proteinase K was further hydrolyzed on the basis of alcalase hydrolysis. The optimal hydrolysis conditions were reaction time of 2 h, substrate concentration of 10 mg mL−1, enzyme addition amount of 2.8 U mg−1, reaction temperature of 60 °C, and hydrolysate chelation ability of 12.16 mg g−1, thereby corresponding to a degree of hydrolysis (DH) of 35.30%. On the basis of the hydrolysis by proteinase K, alcalase was further hydrolyzed, and the optimal hydrolysis conditions were reaction time of 3 h, substrate concentration of 10 mg mL−1, enzyme addition amount of 8.0×105 U mg−1, reaction temperature of 50 °C, and hydrolysate chelation ability of 13.72 mg g−1, thereby corresponding to a DH of 29.32%. Zein Zn2+-chelating peptide is significant for 1,1-diphenyl-2-picrylhydrazyl free radicals, hydroxyl radicals, and ABTS·+. The clearance effect is positively correlated with the mass concentration of the polypeptide. Zein Zn2+-chelating peptide has good Zn2+ chelating ability and antioxidant activity. Hence, it has broad research prospects for new dietary supplements.
N-Methyltyramine (N-MeTA) is known as a gastrin-releasing factor in beer. In this study, the agonistic actions of N-MeTA as well as tyramine (TA)/β-phenylethylamine (PEA) and their other N-methylated derivatives were examined to elucidate their structure-activity relationships, using a secreted placental alkaline phosphatase (SEAP)-based reporter assay in HEK-293 cells transiently expressing a G protein-coupled receptor, human trace amine-associated receptor 1 (hTAAR1). We detected the agonistic actions of six test compounds, including N-MeTA (EC50 = 6.78 µM), on hTAAR1. The agonistic actions were reduced depending on the number of N-methyl groups introduced into TA and PEA; the order of potency is PEA > N-methylphenylethylamine > TA ≈ N,N-dimethylphenylethylamine ≥ N-MeTA ≥ N,N-dimethyltyramine. Taken together with our previous study on TA/PEA as agonists for hTAAR1 in the stomach, this finding suggests that hTAAR1 might be the primary target of N-MeTA in the stomach; however, the agonistic potency of N-MeTA is weaker compared to TA and PEA.