Determination of steroidal saponins in different organs of yam (Dioscorea pseudojaponica Yamamoto)

Yams (Dioscorea spp.) are perennial trailing rhizome plants. Steroidal saponins, furostanol and spirostanol glycosides are the marked functional compounds in yams. In this investigation, a C18 solid phase extraction method was developed for yam saponins purification. The contents of saponins in various organs of yam (Dioscorea pseudojaponica Yamamoto) were also determined. Results showed that the recoveries of yam saponins extracted by the developed method were about 99.48–100.08% when the saponins (each saponin weighed 0.20, 0.50 and 1.00 mg) passing through the C18 cartridge. The extractive method could efficiently reduce the interferences from impurities in yam saponin extracts prior to HPLC analysis. The recoveries of added saponins in different yam organs were 98.34–99.92% for tuber flesh, 95.98–98.89% for tuber cortex, 97.89–99.44% for rhizophor, 93.82–98.01% for leaf and 93.87–97.65% for vine, respectively. The yam tuber cortex had the highest amount of saponins (582.53 μg/g dw), which was higher than that existed in the tuber flesh (227.86 μg/g dw) about 2.55 times. The contents of saponins in the rhizophor, leaf and vine of yam were 29.39, 24.41 and 23.96 μg/g dw, respectively.     

Effect of endogenous glycosidase on stability of steroidal saponins in Taiwanese yam (Dioscorea pseudojaponica yamamoto) during drying processes

The effect of different drying methods on steroidal saponins, furostanol and spirostanol glycosides, in Dioscorea pseudojaponica Yamamoto, were studied. The yams were either steam-blanched or not blanched before drying. Results showed that solar and shaded drying without prior blanching would cause significant changes of yam saponins; hot air drying caused slight variation, and other drying methods showed almost no change. A similar phenomenon was observed in a model system containing crude yam saponin extract; it indicated that higher temperature and light exposure had very little effect on the stability of yam saponins during drying. On the other hand, the endogenous glucosidase in yam might play an important role in altering the saponin structures during drying. This was confirmed by a model experiment; a crude furostanol glycoside 26-O-β-glucosidase prepared from yam was shown to remove the glucose at position C-26 of the furostanol glycoside structure and change it to the respective spirostanol glycoside.     

Physicochemical changes occurring during post-harvest hardening of trifoliate yam (Dioscorea dumetorum) tubers

Processing of Dioscorea dumetorum tubers into flour could be a means of adding a longer-term value to this tropical plant with a high nutritional potential but which presents a post-harvest hardening problem. This study was carried out in order to investigate the effect of storage under prevailing tropical ambient conditions (19–28 °C, RH 60–85%) for 56 days on the physicochemical characteristics of flours produced from hardened tubers. With the exception of bulk density, the results showed that all the physicochemical properties measured (water absorption capacity, oil absorption capacity, water solubility index, hydrophilic–lipophilic index, swelling capacity and least gelatinising concentration) were significantly influenced by tuber storage time (P<0.05). In general, the physicochemical indices increased with storage in at least two phases, from days 2 to 21 and from days 28 to 56. Since sprouting of most tubers was observed after 28 days of storage, the results suggest that post-harvest hardening and sprouting influence the above-mentioned indices of flours produced from D. dumetorum tubers.     

Influence of fermentation on some quality characteristics of trifoliate yam (Dioscorea dumetorum) hardened tubers

Processing of Dioscorea dumetorum tubers into flour could be a means of adding a longer-term value to this tropical plant with a high nutritional potential but which possesses a post-harvest hardening problem, characterised by a hard-to-cook defect. In an attempt to investigate the changes leading to fermentation of hardened tubers, CIE L^∗a^∗b^∗ parameters and some physicochemical properties of the yams were monitored. Four fermentation periods (0, 2, 4, 7 and 14 days) under ambient temperature (23 ± 5 °C) in the presence and absence of oxygen were studied. The results showed that fermentation significantly (p ? 0.05) increased a^∗ and b^∗ parameters, and decreased L^∗ parameter. However, browning affected more tubers fermented in the presence of oxygen. All the anti-nutrients evaluated (total phenols, phytic acid, oxalates, trypsin inhibitors and α-amylase inhibitors) decreased by significant levels (p ? 0.05) within 14 days of fermentation. However, the rates of anti-nutrient losses varied for each constituent and followed first-order reaction kinetics.     

Effect of short-term storage on phenolic content,o-diphenolase and peroxidase activities of cut yam tubers (Dioscorea sp)

The effect of short-term storage on the protein, phosphorus and phenolic content as well as peroxidase and o-diphenolase activities of cut, harvested Jamaican yam (Dioscorea sp) tubers (D rotundata. D alata and D cayenensis) was studied. There was an initial increase in the total phenolic content up to the third week of storage followed by a gradual decrease to the sixth week. Phenolic content was found to be highest in D cayenensis followed by D rotundata and D alata. The activities of peroxidase (EC 1. 11. 1. 7) and o-diphenolase (EC 1. 10.3.1) increased steadily up to the third week of storage and thereafter decreased to the fifth week. The intensity and rapidity of browning in tubers when cut, correlated very closely with the tuber o-diphenolase and phenolic content levels while the onset of rotting correlated with the peroxidase activity levels in the species studied.     

Carbohydrate content of potato (Solanum tuberosum L.) tubers treated with Isopropyl-N (3-chlorophenyl) carbamate under different storage conditions

Post harvest application of Isopropyl-N (3-chlorophenyl) carbamate considerably reduced the degradation of starch when potato tubers were stored in an evaporative cooling chamber. The starch degraded at a faster rate when tubers were kept under refrigerated and room storage conditions.     

气相离子迁移谱结合化学计量法快速鉴别不同产地连翘

分析不同产地芋头挥发性有机化合物组成差异,并构建芋头产地溯源的可视化指纹图谱。采用气相离子迁移谱法对不同产地芋头的挥发性物质进行测定,结合主成分分析（PCA）实现样品产地的快速区分,进一步筛选芋头中差异挥发性物质。结果表明,在不同产地芋头中,共检测到45个信号峰,鉴定出26种化合物,包括单体和部分化合物的二聚体。主成分分析将芋头分为3类,其中,靖江香沙芋和奉化芋头的挥发性物质较为相似,而与荔浦芋头、沙沟芋头差别很大。异丙醇、2-甲基-乙酸丁酯、辛酸甲酯是区别不同芋头的特征标记物。该方法直观、快速,为地方特色芋头的区分提供了新方法和技术支持。     

Effects of catching methods on quality changes during storage of cod (Gadus morhua)

The catching method, storage time and composition of fish are factors that influence the quality of fish. Different opinions have been expressed concerning the effect of catching methods on the fish quality. In this work cod caught at the same time and location, using different catching methods (gillnet and longline) has been stored for up to 16 days. The same soaking time was used for both fishing gears. No differences due to fishing gear was observed in the quality attributes QIM score, water content, TVN, DMA, TMA, TMAO, Freshmeter-readings, total viable count, sulphide producing bacteria and P. phosphoreum during storage. The catching method had significant influence on pH only. It is shown that the pH of the fish caught by gillnet is lower than pH of fish caught by longline. It is also shown that fish caught by gillnet have higher K-factor than fish caught by longline. The pH of the fish muscle is closely correlated to K-factor; higher K-factor supports lower pH.It is also shown that by using the quality parameters water content, TVN, DMA, QIM score, Freshmeter-readings, TVC, sulphide producing bacteria, and P. phosphoreum, the storage time in ice can be predicted with a correlation of 0.99 and a prediction error of 0.8 day.     

Changes in the catechin and epicatechin content of grape seeds on storage under different water activity (aw) conditions

Storage effect on antioxidant content and capacity of grape seeds under different a_w conditions (a_w 0.33; 0.53; 0.75/50 days, 25 °C) was examined. Total phenol content (determined by the Folin–Ciocalteu method) decreased during storage though changes were trivial for samples stored at 33% or 53% RH. High level of humidity (75%) accelerated degradation and resulted in a ∼50% reduction of total phenol content. Minor loss of the DPPH radical scavenging activity (%RSA) of the extracts was observed. Catechin and epicatechin content monitored by RP-HPLC was reduced during storage, particularly at 75% RH. Epicatechin content proved to be less sensitive to water activity conditions than catechin content. Results of various in vitro assays (Folin–Ciocalteu, FRAP, DPPH, ABTS, CBA, ORAC and copper induced liposome oxidation) did not support difference in terms of resistance to oxidation. Based on the continuous release of gallic acid, our finding was related to hydrolytic reactions. Control of a_w of grape seeds can be of practical importance for the wine industry.     

Effects of different freezing treatments on physicochemical responses and microbial characteristics of Japanese sea bass (Lateolabrax japonicas) fillets during refrigerated storage

In order to establish an effective freezing method for quality control, the present research evaluated the effects of the different freezing treatments on the quality of Japanese sea bass (Lateolabrax japonicas) over a period of 20 days storage at 0 ± 1 °C. Fish pH value, total volatile basic nitrogen (TVB-N), K-value, trimethylamine nitrogen (TMA-N), drip loss, hardness, color, biogenic amines, microbiological characteristics were measured. Sea bass fillets were stored at −18 °C (T1), −55 °C for 24 h and then −18 °C (T2), −55 °C (T3) for 3 months prior to refrigerated storage. T2 showed lower TVB-N, pH value, biogenic amines and drip loss than T3 and T1 did. Significant lower value of bacterial loads, b* value and hardness were observed in T1, T2 and T3 than those of control group. No significant differences were observed among T1, T2 and T3 for TMA-N and a* value. The study demonstrated that Japanese sea bass fillets treated with −55 °C for 24 h and then −18 °C up to 3 months maintain better quality during refrigerated storage.     

Effects of tuber storage protein of yam (Dioscorea alata cv. Tainong No. 1) and its peptic hydrolyzates on spontaneously hypertensive rats

Yam storage protein (YSP) was purified from tubers of Dioscorea alata L. Tainong No. 1 (TN1) to homogeneity by DE‐52 ion‐exchange chromatography. The short‐term (24 h) and long‐term (25 days) antihypertensive effects of YSP‐TN1 and its peptic hydrolyzates (PH‐TN1) were measured in spontaneously hypertensive rats (SHRs). For 24‐h antihypertensive measurements, SHRs (age 10 weeks, body weight from 240 to 250 g) were administered orally once (YSP‐TN1 and PH‐TN1, 40 mg kg^?1 SHR) to measure the mean blood pressure (MBP), systolic blood pressure (SBP) and diastolic blood pressure (DBP). For a long‐term antihypertensive measurement, SHRs (age 12 weeks, body weight from 250 to 270 g) were administered orally once a day for 25 days (YSP‐TN1, 40 mg kg^?1 SHR) to measure SBP, DBP and MBP. Captopril (10 or 15 mg kg^?1 SHR) was used as a positive control. It was found that short‐term administration of 40 mg kg^?1 SHR of YSP‐TN1 and PH‐TN1 effectively lowered SHRs' MBP, SBP and DBP (For YSP‐TN1, the lowest blood pressure was reached in the fourth hour and for PH‐TN1 in the eighth hour). The lasting effects of PH‐TN1 on reduced SHRs' BP were better than those of YSP‐TN1 for one oral administration. For oral administration of 40 mg YSP‐TN1 kg^?1 SHR, the reduced MBP was 21.5 mmHg, which was comparable to 25.2 mmHg (the fourth hour) of 10 mg captopril kg^?1 SHR oral administration. For oral administration of 40 mg PH‐TN1 kg^?1 SHR, the reduced MBP was 33.7 mmHg, comparable to 38.4 mmHg (the fourth hour) of 15 mg captopril kg^?1 SHR. For long‐term 25‐day oral administration of 40 mg YSP‐TN1 kg^?1 SHR once a day, it was found that a feeding trial of YSP‐TN1 effectively lowered SHRs' SBP, DBP and MBP. The greatest reduction in SHRs' blood pressure was reached on the ninth day, for the reduced SBP, 27.7 mmHg; for the reduced DBP, 28.3 mmHg; and for the reduced MBP, 27.5 mmHg. Copyright © 2006 Society of Chemical Industry     

Biotransformation of (R)-(+)- and (S)-(−)-limonene to α-terpineol by Penicillium digitatum— investigation of the culture conditions

The biotransformation of (R)-(+)- and (S)-(−)-limonene by Penicillium digitatum was investigated. One strain of P. digitatum was able to convert (R)-(+)-limonene to pure (R)-(+)-α-terpineol in 8 h with a yield of up to 93%. It was found that (R)-(+)-limonene was converted much better into α-terpineol than (S)-(−)-limonene, and that no significant chemical conversion of the substrate occurred in control flasks at pH 3.5. The culture conditions involved such as the type and concentration of co-solvent applied and the sequential addition of substrate were investigated, taking into account some findings on the physical behaviour of the system. The highest bioconversion yields were obtained when the substrate was applied as a diluted solution in EtOH.     

Effects of tea polyphenol coating combined with ozone water washing on the storage quality of black sea bream (Sparus macrocephalus)

The present research evaluated the effects of tea polyphenol (TP) combined with ozone water (O₃) on the quality of black sea bream (Sparus macrocephalus) over a period of 15 days storage at 4 °C. A solution of TP (0.2%, w/v) was used to coat the fish after washing with ozone water (1 mg/L). Fish physicochemical (pH, K value, peroxide value, thiobarbituric acid, total volatile basic nitrogen, trimethylamine, texture, and colour), sensory, and bacteriological characteristics were all analysed. TP + O₃ treatment effectively reduced nucleotide breakdown, lipid oxidation, protein decomposition, and microbial growth, and maintained better characteristics of texture, colour, and sensory compared with the control. The efficiency of TP + O₃ treatment was also better than that of TP treatment or O₃ treatment alone. Therefore, tea polyphenol coating combined with ozone water prewashing may be a promising method of maintaining the storage quality of black sea bream and of extending fish post-mortem shelf-life during 4 °C storage.     

Effects of different food commodities on larval development and α-amylase activity of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

The present work was undertaken to study the influence of four commodities (wheat flour, dates, sorghum and barley) on Plodia interpunctella post-embryonic development. Larval weight, larval mortality, pupation and adult emergence were recorded. The study also aimed to find out the effect of these commodities on protein and glycogen production as well as on α-amylase activity. Results indicated that the weight of fourth instar larvae placed on dates increased gradually. Percentage mortality was low. Pupation and adult emergence were delayed. In contrast, the weight of larvae placed on wheat flour, sorghum or barley remained low. Pupation and adult emergence occurred sooner than among those placed on dates and the percentage mortality was highest for larvae placed on barley. Results also showed that protein content and α-amylase activity were lower for larvae placed on dates than for those placed on other commodities. The biochemical composition of different commodities showed that dates are a rich source of glucose, while their protein and starch contents were very low as compared to the other commodities. In contrast, wheat flour, sorghum and barley contained large amounts of starch and protein and low amounts of glucose. Thus, the reduction in α-amylase activity was probably due to the high levels of glucose in dates.     

Low temperature post-harvest storage of New Zealand Taewa (Maori potato): Effects on starch physico-chemical and functional characteristics

Fresh tubers from four traditional Taewa (Maori potato) cultivars (Karuparera, Tutaekuri, Huakaroro and Moemoe) and one modern potato cultivar (Nadine) of New Zealand, were stored at 4 °C and 80–90% relative humidity for six months after harvest. Starch was isolated from tubers after every three month period, and its physico-chemical and functional properties measured. Considerable changes in these properties occurred during storage. The extent of changes varied significantly from cultivar to cultivar. Starch swelling power, solubility and light transmittance decreased during tuber storage while a slight increase was observed in starch amylose content. The starch granule size distribution shifted to smaller granule size during tuber storage. Scanning electron micrographs showed degradation/erosion and pitting on the surfaces of many of the starch granules isolated from stored tubers. Transition temperatures and enthalpies of gelatinization of the starches increased somewhat during tuber storage, suggesting that changes in the stability of starch crystalline structures had occurred. Pasting, viscoelastic and texture profile analysis (TPA) characteristics of starch gels were found to have been influenced by tuber storage time for all the cultivars, but to the greatest extent for Nadine and Huakaroro. Gels made from starches from the stored tubers had a reduced tendency towards retrogradation as evidenced by the decrease in syneresis (%) during gel storage at 4 °C.     

Phenolic contents and antioxidant activities of bitter gourd (Momordica charantia L.) leaf, stem and fruit fraction extracts in vitro

Bitter gourd (Momordica charantia L.) has long been regarded as a food and medicinal plant. We investigated the antioxidant activity of the water extract of leaf, stem and fruit fractions by several in vitro systems of assay, namely DPPH radical-scavenging activity, hydroxyl radical-scavenging activity, β-carotene–linoleate bleaching assay, ferric reducing/antioxidant power (FRAP) assay and total antioxidant capacity. Total phenolic content was measured by Folin–Ciocalteu reagent. Identification of phenolic compounds was achieved using HPLC with the UV-diode array detection. The extracts of different fractions were found to have different levels of antioxidant activity in the systems tested. The leaf extract showed the highest value of antioxidant activity, based on DPPH radical-scavenging activity and ferric reducing power, while the green fruit extract showed the highest value of antioxidant activity, based on hydroxyl radical-scavenging activity, β-carotene–linoleate bleaching assay and total antioxidant capacity. The predominant phenolic compounds were gallic acid, followed by caffeic acid and catechin. The present study demonstrated that the water extract fractions of bitter gourd have different responses with different antioxidant methods. Total phenol content was shown to provide the highest association with FRAP assay in this present study (R² = 0.948).     

Effects of high-pressure treatment on the microflora of oysters (Crassostrea gigas) during chilled storage

The microbiological quality of oysters high-pressure (HP)-treated in-shell at 260 MPa for 3 min, or 500 or 800 MPa for 5 min and then stored at 2 °C, were investigated. Microbial counts after HP treatment showed that the bacterial load was reduced after treatment at all pressures to levels below the detection limit. Randomly-selected isolates from the total aerobic viable counts of untreated and HP-treated oysters after 14 days of storage were identified by the API identification system. Bacteria isolated from oysters HP-treated at 260 MPa were Shewanella putrifaciens and Pseudomonas fluorescens. For oysters HP-treated at 500 or 800 MPa, the main bacteria isolated were Pseudomonas spp. Vibrio spp. comprised 44% of the microflora in untreated oysters after storage for 14 days at 2 °C, but no Vibrio were detected in HP-treated oysters. This study confirmed that HP processing can inactivate microorganisms and delay microbial growth in chilled stored oysters.

Industrial relevance

High-pressure (HP) treatment is being increasingly employed for commercial processing of oysters but no studies of the microflora of HP-treated in-shell oysters have been reported. HP treatment significantly changed the microflora of oysters and apparently has good potential for inactivation of Vibrio spp as HP treatment, in combination with adequate chilled storage, can improve the microbiological shelf-life and safety of oysters.     

4-羟基-2,5-二甲基-3(2H)呋喃酮对单增李斯特菌AI-2类群体感应的干扰效应

利用群体感应抑制剂靶向干扰病源菌已成为有效控制致病性危害的突破口。本研究通过测定菌体浓度、哈氏弧菌BB170报告菌的发光值,研究不同浓度4-羟基-2,5-二甲基-3(2H)呋喃酮(DMHF)作用下单增李斯特菌(L.m)的生长与信号分子AI-2活性;通过半固体穿刺法、结晶紫法及溶血平板法检测L.m的动力、生物膜及溶血性,来评价DMHF对L.m AI-2类QS的干扰效应。结果表明,≤ 200 μg/mL的DMHF能推迟L.m的生长,且明显抑制了L.m AI-2的活性,实验组的AI-2活性值均低于阴性对照组的40%,由此可判定DMHF是AI-2类QS的抑制剂;当DMHF浓度为100 μg/mL时能明显抑制L.m的运动能力;50、100和200 μg/mL的DMHF对L.m生物膜的形成抑制率分别为29.72%、44.88%和75.27%;200 μg/mL的DMHF完全抑制溶血环的产生,本研究为利用DMHF作AI-2类QS的抑制剂提供依据。     

水翁花蕾提取物DMC对胰脂肪酶的抑制作用研究

本文主要探讨了2',4'-二羟基-6'-甲氧基-3',5'-二甲基查耳酮(2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone,DMC)对胰脂肪酶(Pancreatic Lipase,PL)的抑制作用及作用机理。以4-硝基苯丁酸酯为底物,采用对硝基苯酚法检测DMC对PL活性的影响,采用紫外光谱法、荧光光谱法以及分子对接法研究DMC与PL的相互作用。结果表明:DMC对PL有抑制作用,半数抑制浓度为50.01±3.56 μmol/L,酶动力研究表明DMC是PL的竞争型抑制剂;光谱实验结果显示DMC的加入使PL发生了荧光猝灭,猝灭类型为动态猝灭;同步荧光及三维荧光实验表明DMC不会改变PL构象;热力学参数ΔG<0,两者的相互作用是自发进行,ΔH<0,ΔS<0,表明DMC与PL的相互作用力主要为氢键和范德华力;分子对接实验进一步验证了以上结果。由此可见,DMC具有作为PL抑制剂的潜能。