Influence of natural coagulants on isoflavones and antioxidant activity of tofu

Inactivation Kinetics and Membrane Potential of Pathogens in Soybean Curd Subjected to Pulsed Ohmic Heating Depending on Applied Voltage and Duty Ratio

The aim of this research was to investigate the efficacy of the duty ratio and applied voltage in the inactivation of pathogens in soybean curd by pulsed ohmic heating (POH). The heating rate of soybean curd increased rapidly as the applied voltage increased, although the duty ratio did not affect the temperature profile. We supported this result by verifying that electrical conductivity increased with the applied voltage. Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in soybean curd were significantly (P < 0.05) inactivated by more than 1 log unit at 80 Vrms (root mean square voltage). To elucidate the mechanism underlying these results, the membrane potential of the pathogens was examined using DiBAC4(3) [bis-(1,3-dibutylbarbituric acid)trimethine oxonol] on the basis of a previous study showing that the electric field generated by ohmic heating affected the membrane potential of cells. The values of DiBAC4(3) accumulation increased under increasing applied voltage, and they were significantly (P < 0.05) higher at 80 Vrms, while the duty ratio had no effect. In addition, morphological analysis via transmission electron microscopy showed that electroporation and expulsion of intracellular materials were predominant at 80 Vrms Moreover, electrode corrosion was overcome by the POH technique, and the textural and color properties of soybean curd were preserved. These results substantiate the idea that the applied voltage has a profound effect on the microbial inactivation of POH as a consequence of not only the thermal effect, but also the nonthermal effect, of the electric field, whereas the duty ratio does not have such an effect.IMPORTANCE High-water-activity food products, such as soybean curd, are vulnerable to microbial contamination, which causes fatal foodborne diseases and food spoilage. Inactivating microorganisms inside food is difficult because the transfer of thermal energy is slower inside than it is outside the food. POH is an adequate sterilization technique because of its rapid and uniform heating without causing electrode corrosion. To elucidate the electrical factors associated with POH performance in the inactivation of pathogens, the effects of the applied voltage and duty ratio on POH were investigated. In this study, we verified that a high applied voltage (80 Vrms) at a duty ratio of 0.1 caused thermal and nonthermal effects on pathogens that led to an approximately 4-log-unit reduction in a significantly short time. Therefore, the results of this research corroborate database predictions of the inactivation efficiency of POH based on pathogen control strategy modeling.

The utilization of bilimbi (Averrhoa bilimbi) and lime (Citrus aurantifolia) juices as natural acid coagulants for tofu production

The influences of coagulation conditions on the characteristics of tofu have been investigated by many studies, with limited perspectives on the utilization of organic acid coagulants. Hence, this research aimed to study the psychochemical and functional properties of tofu coagulated by bilimbi (Averrhoa bilimbi) and lime (Citrus aurantifolia) juices. The highest tofu protein content was quantified for tofu prepared with 20% bilimbi and 5% lime juices, as much as 52.11 and 52.03% (DW), respectively. The corresponding yield was 73.46 and 69.17%. The hardness (155.98 g), gumminess (116.45 g), and chewiness (112.69 g) of treated tofu were found significantly higher than commercial tofu (p < 0.05). Total phenolic content of commercial tofu was about 370.09 μg GAE/g sample (DW). This value was significantly higher than that of treated tofu (p < 0.05). However, the antioxidant activity of the commercial tofu was lower than tofu coagulated with fruit juices. Based on SDS-PAGE analysis, protein band for 11S fraction of tofu coagulated by bilimbi and lime juices were thicker than that of commercial tofu. These small molecular weight peptides might contribute for higher antioxidant activities of tofu coagulated by bilimbi and lime juices. Conclusively, bilimbi and lime juices are potent natural acid coagulants for enhancing the physicochemical and functional properties of tofu.

Composition, texture and microstructure appraisal of paneer coagulated with sour fruit juices

The investigation studied the effect of sour fruit juices as coagulants on the physico-chemical properties, phytonutrients, sensory scores, texture profile analysis (TPA) and microstructure using scanning electron microscopy (SEM) of paneer. Paneer was coagulated using citric acid solution (control), lemon or amla juice. The total solids and protein recovery were higher using amla juice while fat recovery was more in control than with the other two coagulants. The mineral profile indicated that calcium content was higher in lemon and amla paneer than citric whereas sodium was highest in citric sample. Paneer collected using fruit juices exhibited higher quantity of functional components studied i.e. antioxidant activity, ascorbic acid, total phenols and tannins than control. Also, it scored high for sensory attributes of appearance/color, body and texture, mouthfeel, flavor and overall acceptability but exhibited disparate values for TPA (hardness, adhesiveness, gumminess and resilience) and discrete structures under SEM.

A Comprehensive Screening and Identification of Genistin Metabolites in Rats Based on Multiple Metabolite Templates Combined with UHPLC-HRMS Analysis

Genistin, an isoflavone belonging to the phytoestrogen family, has been reported to possess various therapeutic effects. In the present study, the genistin metabolites in rats were investigated by UHPLC-LTQ-Orbitrap mass spectrometer in both positive and negative ion modes. Firstly, the data sets were obtained based on data-dependent acquisition method and then 10 metabolite templates were established based on the previous reports. Then diagnostic product ions (DPIs) and neutral loss fragments (NLFs) were proposed to efficiently screen and ascertain the major-to-trace genistin metabolites. Meanwhile, the calculated Clog P values were used to identify the positional isomers with different retention times. Consequently, a total of 64 metabolites, including prototype drug, were positively or putatively characterized. Among them, 40 metabolites were found according to the templates of genistin and genistein, which was the same as the previous research method. After using other metabolite templates, 24 metabolites were added. The results demonstrated that genistin mainly underwent methylation, hydrogenation, hydroxylation, glucosylation, glucuronidation, sulfonation, acetylation, ring-cleavage and their composite reactions in vivo biotransformation. In conclusion, the research not only revealed the genistein metabolites and metabolic pathways in vivo comprehensively, but also proposed a method based on multiple metabolite templates to screen and identify metabolites of other natural compounds.

Impact of protein-rich meals on glycaemic response of rice

Asians typically consume carbohydrate-rich and high-glycaemic-index diets that have been associated with an increased risk of developing type 2 diabetes. Rice is rarely eaten alone such that it is of interest to investigate the effects of co-ingesting different protein-rich meals with rice on insulin and glycaemic response. This study had a randomised, controlled, non-blind, cross-over design in which fifteen healthy Chinese male participants were required to come on non-consecutive days. Five rice-based test meals were served: rice alone (control), rice with fish (RWF), rice with egg white (RWE), rice with soya beancurd (taukwa) (RWT) and rice with chicken (RWC). The control meal consisted of 50 g of available carbohydrate, whereas all other test meals contained additional 25 g of protein. RWT was the only meal that showed significantly lower glucose response when compared with the control (P<0·05). RWF and RWE had significantly higher insulin response, but no significant increase was observed in RWT and RWC when compared with the control (P<0·05). RWT and RWF showed significantly higher glucagon secretion as compared with the control (P<0·05). The four test meals studied showed varying effects, with RWT showing the greatest reduction in glycaemic response. Therefore, the ingestion of soya beancurd with rice may have a direct impact on reducing the risk in Asians transiting from being pre-diabetics to diabetics.

Evaluation and Characterization of Malabar Tamarind [Garcinia cambogia (Gaertn.) Desr.] Seed Oil

The objective of this study is to evaluate the chemical compounds present in the Malabar tamarind seed oil. The oil was extracted from the seeds of Malabar tamarind fruits collected from NBPGR Regional station, Thrissur. The seeds yielded 46.5 % of oil. Parameters such as the peroxide value, iodine value, saponification value, and acid value of the extracted Malabar tamarind seed oil were determined. These values were used to predict the quality of fatty acid methyl esters present in the oil. UV absorption spectroscopy of the oil showed hypsochromic shift, and the maximum absorbance was at 269 nm. The Fourier Transform Infrared Spectrum revealed the presence of olefin hydrogen and carbonyl group of ester compounds in the oil sample. The evaluation of the chemical compounds in the oil using gas chromatography coupled with mass spectrometry (GC-MS) revealed that, a total of five fatty acid methyl esters were present in the oil sample. Among the five fatty acid esters present in the Malabar tamarind seed oil, Methyl 16-methyl heptadecanoate (54.57 %) was found to be the predominant compound. This study also supports the presence of olefins in the long chain fatty acids from Nuclear Magnetic Resonance (NMR) data. There is a significant correlation between the properties and the characteristic profile of the oil sample. This study is the first report that shows Malabar tamarind as a promising source of oil seeds.

Effect of ultrasound assisted extraction upon the Genistin and Daidzin contents of resultant soymilk

The purpose of this study was to determine the effect of ultrasound treatment on the contents of daidzin, genistin, and their respective aglycones, daidzein and genistein, in resultant soymilk. Soybean slurry was exposed to ultrasound treatment, filtered, and placed in an ultrasound cleaning bath set with different frequencies (35and 130 KHz), treatment temperatures (20 and 40 °C), and times (20, 40, and 60 min). Concentrations for these isoflavones were determined using reverse-phase high-performance liquid chromatography. Results indicated that both frequencies significantly (p < 0.05) increased isoflavone content (IC), glycosides, and aglycones in extracted soymilk. These results were attributed to induced cavitation, which increases the permeability of plant tissues. However, the frequency of 35 kHz caused a noticeably higher increase in IC than 130 kHz. Results also revealed significant increases in IC with increased sonication time (from 20 to 60 min) and with increased temperature (from 20 to 40 °C).

Fumigant, contact, and repellent activities of essential oils against the darkling beetle, Alphitobius diaperinus

The fumigant, contact, and repellent activities of four essential oils extracted from Citrus limonum (Sapindales: Rutaceae), Litsea cubeba (Laurales: Lauraceae), Cinnamomum cassia, and Allium sativum L. (Asparagales: Alliaceae) against 6th instars and adults of the darkling beetle, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), one of the main pests of materials and products of Juncus effuses L. (Poales: Juncaceae) during the storage period, were assayed, and chemical ingredients were analyzed with gas chromatography-mass spectrometry in this study. While the major ingredients found in C. limonum and C. cassia were limonene and (E)-cinnamaldehyde, the main constituents of L. cubea were D-limonene, (E)-3,7-dimethyl-,2,6-octadienal, (Z)-3,7-dimethyl,2 ,6-octadienal, and diallyl disulphide (18.20%), while the main constituents of and A. sativum were di-2-propenyl trisulfide and di-2-propenyl tetrasulfide. The fumigation activities of A. sativum and C. limonum on A. diaperinus adults were better than those of the other two essential oilss. The toxicities of A. sativum and C. limonum were almost equitoxic at 96 hr after treatment. Essential oils from Allium sativum and L. cubeba also showed good contact activities from 24 hr to 48 hr, and toxicities were almost equitoxic 48 hr posttreatment. The repellent activities of A. sativum and L. cubeba oils on 6th instars were also observed, showing repellence indexes of 90.4% and 88.9% at 12 hr after treatment, respectively. The effects of A. sativum on AChE activity of 6th instars of A. diaperinus were strongest compared to the other essential oils, followed by C. limonum, L. cubeba, and C. cassia. These results suggest that the essential oils of C. limonum and A. sativum could serve as effective control agents of A. diaperinus.

Functional properties of autolysate and enzymatic hydrolysates from yam tsukuneimo (Dioscorea opposita Thunb.) tuber mucilage tororo: antioxidative activity and antihypertensive activity

Yam tsukuneimo tuber mucilage tororo hydrolysates were prepared by autolysis and three different peptic enzymes. Except for pepsin hydrolysate, tororo was perfectly digested. Each hydrolysate for 100 mg/ml significantly prolonged the induction period of auto-oxidation of linoleic acid, which was similar to 5 mM ascorbic acid. These hydrolysates also possessed high scavenging activities such as superoxide anion radicals, hydroxyl radicals, and DPPH radicals. Moreover, high antihypertensive activities were detected in these hydrolysates except for autolysate, which were similar to various fermented foods such as miso, natto, sake, cheese, and so on. Present findings suggest that yam tsukuneimo tuber mucilage tororo may be useful for preventing diseases associated with reactive oxygen species and blood pressure in the body system and it can fully absorb the useful components from it to digest using the gastrointestinal enzymes.

Cloud-point extraction and reversed-phase high performance liquid chromatography for analysis of phenolic compounds and their antioxidant activity in Thai local wines

A cloud-point extraction (CPE) was developed for the determination of 12 phenolic compounds (i.e. gallic acid, procatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, guaiacol, p-cresol, o-cresol and 3,5-xylenol) using reversed-phase high performance liquid chromatography (RP-HPLC) with photodiode array (PDA) detection. The optimum CPE conditions were 2.0% (w/v) Triton X-114, 3.0% (w/v) Na2SO4 and 20-min equilibrated at 45 °C. The surfactant-rich phase was then analyzed by HPLC using a Symmetry C18 column, gradient mobile phase of acetonitrile and 1% (v/v) acetic acid, and PDA detection at 280 nm. Under the optimum condition, the target phenolic compounds were separated within 25 min. CPE gave higher enrichment factor up to 15-fold compared to that of direct analysis. The proposed method showed good analytical performances with limits of detection in the range 0.01-0.1 mg L(-1) and precisions with relative standard deviation (RSD) lower than 5% for retention time and 10% for peak area. The method was successfully applied to the analysis of phenolic compounds in Thai local wine samples. Gallic acid, procatechuic acid, and vanillic acid were the highest phenolics found in the studied wines with the contents up to 172.4, 99.1, and 26.6 mg L(-1), respectively. The recovery of the spiked wine samples (0.5, 1.0, and 2.0 mg L(-1)) were obtained in the range of 90.4-110%. High total phenolic content, total flavonoids, and antioxidant activity (DPPH method) in the studied wines were also observed.