Optimizing the operation of a two-phase anaerobic digestion system digesting grass silage

This paper examines the optimization of an existing two-phase anaerobic digestion process using grass silage as a feedstock. The system comprises 6 leach beds connected to an upflow anaerobic sludge blanket (UASB). The existing system produced 305 L CH(4) kg(-1) VS added at an overall retention time of 42 days (6 leach beds emptied and fed sequentially every 7 days in series). The desired improvements were a reduction in retention time with increased methane production. It was noted in the existing system that biogas production and COD levels fell off in the last 2 days of each 7-day cycle. Thus the first change involved reduction in retention time to 30 days (6 leach beds fed sequentially every 5 days in series). This lead to a slight improvement in methane production (310 L CH(4) kg(-1) VS added). The second change was effected by separation of flows to the first stage (leach beds) and the second stage (UASB) through addition of an extra pump to optimize leaching. This led to an increase in CH(4) production (341 L CH(4) kg(-1) VS). The overall improvement from the existing system was an increase of 11.8% in methane production and a reduction in size or retention time of 40% (42 days decreased to 30 days retention time).     

Evaluation of hydraulic efficiency of disinfection systems based on residence time distribution curves

Hydraulic efficiency is a vital component in evaluating the disinfection capability of a contact system. Current practice evaluates these systems based upon the theoretical detention time (TDT) and the rising limb of the residence time distribution (RTD) curve. This evaluation methodology is expected because most systems are built based on TDT under a "black-box" approach to disinfection system design. Within recent years, the proliferation of computational fluid dynamics (CFD) has allowed a more insightful approach to disinfection system design and analysis. Research presented in this study using CFD models and physical tracer studies shows that evaluation methods based upon TDT tend to overestimate, severely in some instances, the actual hydraulic efficiency as obtained from the system's flow and scalar transport dynamics and subsequent RTD curve. The main objective of this study was to analyze an alternative measure of hydraulic efficiency, the ratio t(10)/t(90), where t(10) and t(90) are the time taken for 10 and 90% of the input concentration to be observed at the outlet of a system, respectively, for various disinfection systems, primarily a pipe loop system, pressurized tank system, and baffled tank system, from their respective RTD curves and compare the results to the current evaluation method.     

茯苓-丹参共发酵体系及其产物对糖尿病小鼠降血糖作用的影响

采用茯苓真菌作为发酵菌株,丹参作为药性基质,在基础发酵培养基中进行双向发酵试验。确定种子液的最佳培养时间,对最佳丹参加入量和发酵时间进行探究,比较共发酵体系与单一体系对胞内多糖和胞外多糖及总黄酮含量的影响,比较共发酵体系与单一体系对糖尿病小鼠血糖水平的影响。结果显示,种子液的最佳培养时间为1 d,培养基中丹参最佳质量浓度为1 g/mL,最佳双向发酵时间为5 d。共发酵体系与单一体系相比显著增加了体系中胞外多糖(15.74 mg/mL)、胞内多糖含量(1.26 mg/mL),同时共发酵体系引入了丹参总黄酮(1.04 mg/mL)。共发酵体系与单一体系相比能有效降低糖尿病小鼠的血糖,提高糖尿病小鼠的葡萄糖耐受力。所制得的茯苓-丹参共发酵产物具有潜在降血糖作用,具有进一步开发保健品的价值。     

食品机械自动定量填充系统的研究与设计

目的设计一种食品机械自动定量填充系统。方法以可编程逻辑控制器(programmable logic controller,PLC)为核心设计控制系统,并采用模糊比例-积分-微分控制算法(proportion integral derivative,PID)提高填充控制系统的精度以及稳定性。结果在400 g重量段,填充重量为(400.35±4.692)g,填充时间平均值为(4.97±0.170)s;在800 g重量段,填充重量平均值(800.47±7.098)g,填充时间平均值为(5.92±0.123)s;在900 g重量段,填充重量平均值(899.98±8.870)g,填充时间平均值为(6.43±0.080)s,填充质量变化率小于2%,并且填充时间小于7 s。结论该设计食品填充精度高,机械稳定性和安全性高,对现有食品包装机械装置具有很大的借鉴意义,有较大的推广价值。     

INHIBITION OF SALMONELLA TYPHIMURIUM ON POULTRY BY THE LACTOPEROXIDASE SYSTEM1

The antibacterial activity of the lactoperoxidase (LP) system on the growth and survival of a naladixic acid resistant strain of Salmonella typhimurium on poultry was determined. The LP system treatment, which consisted of lactoperoxidase (1 μg/ml), potassium thiocyanate (5.9 mM), and hydrogen peroxide (2.5 mM) (final concentrations) in water, reduced the level of Salmonella on inoculated chicken legs. The magnitude of reduction was dependent on temperature and time. For a water temperature of 25C and a time of 30 min, a 13.2% reduction was seen, as compared to a water temperature of 60C and a time of 15 min which showed a 80.6% reduction. In a 48 h shelf-life study, the LP system controlled growth of psychrotrophic bacteria on chicken legs. Hunterlab color values (L, a, b) for chicken thigh skin and oxidative deterioration as measured by TBA values for chicken thigh meat did not significantly differ (p < 0.01 and p < 0.05, respectively) between control and treated thighs.     

Short communication: Effect of automatic postmilking teat disinfection and cluster flushing on the milking work routine

The importance of a consistent and comprehensive milking routine as a critical component of any mastitis control program is well documented. However, as pressure on time increases, farmers are faced with 3 options: (1) adjust the milking routine to suit the time available, (2) undertake the task less thoroughly, or (3) examine which elements of the milking routine can be automated and substitute capital expenditure for labor. A study was undertaken on 5 farms in the United Kingdom in October and November 2007 to assess the effect on milking time of installing a commercial automatic postmilking teat disinfection and cluster back flushing system (ADF). Two of the farms recruited for the study were intending to purchase the ADF system in the near future and 3 farms had already invested in the technology. The farms ranged in size from 120 to 550 cows and included three 90° rapid exit parlors, a herringbone parlor, and an abreast parlor. All 5 farms were visited for 2 successive milkings before the ADF was installed or disabled, and a detailed time and motion analysis was undertaken. After ADF was installed or the system reactivated, a further 2 milkings were monitored. All monitored farms showed a measurable reduction in milking time after the ADF system was installed. However, the magnitude of the reduction was greater than would be expected by simply removing the elements of postmilking teat disinfection and cluster sanitization. The benefits of ADF are greater than simply disinfecting teats and back flushing clusters and the time saving obtained may allow a more structured milking routine that may have additional benefits in terms of mastitis prevention and control.     

Antioxidant activity of Maillard reaction products derived from aqueous glucose/glycine,diglycine, and triglycine model systems as a function of heating time

The purpose of this study was to evaluate the antioxidant activity of Maillard reaction products (MRPs) derived from aqueous glucose/glycine, diglycine, and triglycine model systems as a function of heating time. The pH of MRPs derived from the Glu-G model system decreased markedly as the heating time increased, while MRPs derived from the Glu-Di model system showed the highest increase in absorbance at 420 nm. MRPs derived from the Glu-G model system showed the highest cupric ion chelating ability, while MRPs derived from the Glu-Di model system had the highest ferrous ion chelating activity. MRPs derived from the Glu-Di model system were found to be effective antioxidants in different in vitro assays with regard to the 2,2′-azinobis(3-ethylbenothiazoline-6-sulphonic acid) diammonium salt (ABTS) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging activities and ferric reducing/antioxidant power (FRAP).     

花生红衣中黄烷醇抑制丙烯酰胺效果及其分离鉴定

目的研究花生红衣中提纯的原花青素(peanut skin procyanidins,PSPs-1)在化学模拟体系和食品体系中对丙烯酰胺产生的抑制效果,并对PSPs-1的组成成分进行鉴定。方法以天冬酰胺和葡萄糖反应产生丙烯酰胺作为化学模拟体系,以油炸薯条生成丙烯酰胺作为食品体系,通过HPLC分析PSPs-1对2种体系中丙烯酰胺的抑制效果,并采用反相高效液相色谱-电喷雾-质谱联用(RP-HPLC-ESI-MS/MS)技术对PSPs-1进行鉴定。结果在化学模拟体系中,PSPs-1具有明显的抑制丙烯酰胺生成的效果,并显示出非线性浓度效应,在添加量为0.1 mg/m L时达到最大抑制率,为(51.22?3.15)%;在食品体系中,PSPs-1的浓度及浸渍薯条时间皆对丙烯酰胺的产生有明显抑制效果,并显示一定的量效关系,PSPs-1浓度为0.1 mg/m L达到最大抑制率,为(51.03?2.97)%,且当浸渍时间为90 s时抑制效果最好(50.79±1.86)%。PSPs-1经RP-HPLC-ESI-MS/MS分析和与对照品比较,其可能是由含有儿茶素和表儿茶素的黄烷醇多酚组成。结论由儿茶素和表儿茶素组成的PSPs-1在2种体系中具有明显抑制丙烯酰胺产生的效果。     

The effect of pre-milking teat-brushing on milk processing time in an automated milking system

Cow throughput in an automatic milking system (AMS) is limited by system parameters such as the time required for pre-milking udder preparation and cup attachment, physiological responses of the cow (such as milk let-down and milking-out rate), milking machine features and cow behaviour. A single-factor cross-over design was used to investigate the effect of pre-milking teat brushing on milk processing time in an AMS operating in an extensive grazing farming system. Teat brushing consisted of two roller brushes tracking up each teat three times (total brushing time of up to 45 s/cow). Cows were allocated to one of two treatment groups with either no brushing (NB) or brushing (B) for a 4-week period before being changed to the other treatment. Teat brushing resulted in shorter average cups-on-time (B = 506.1 s, NB = 541.0 s, P = 0.0001), longer average milk processing time (B = 10.30 min, NB = 9.76 min, P = 0.001) and no difference in daily milk yield (B = 14.67, NB = 14.71 kg/cow, P = 0.826). There was no difference between the two treatments in the success of cup attachment (B = 3.76%, NB = 5.10% unsuccessful milking attempts, P = 0.285). The estimated time cost of pre-milking teat brushing was 53 min for every 100 milkings, equivalent to an additional 5-6 milkings for every 100 milkings by an AMS. The importance of these potential time savings is discussed in relation to automatic milking in farming systems that aim for a lower per cow milking frequency and high ratio of cows to AMS.     

Characteristics and antioxidant activity of Maillard reaction products from fructose-glycine oligomer

The pH of Maillard reaction products (MRPs) derived from the Gly model system (Gly) decreased markedly as heating time increased. However the Digly model system (Digly) exhibited the highest increase in absorbance at 294 and 420 nm. Moreover, the loss of fructose and degree of sugar enolization in MRPs derived from the Trigly model system (Trigly) was the highest, whereas the glycine oligomer content in the Digly noticeably decreased as heating time increased. Furthermore, the gel permeation chromatograms (GPC) patterns of all MRP samples exhibited rising intensities as a function of the heating time, whereas the major peaks of each MRP sample were eluted at different retention times as glycine oligomer. Antioxidant activity of each MRP sample was investigated by Fe²⁺ and Cu²⁺ chelating activity, Trolox, ABTS, 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging activity, and ferric reducing ability of plasma (FRAP) assay. MRPs derived from the glycine oligomer were found to be effective antioxidants in different antioxidant activity assays.     

MULTISPECTRAL IMAGING SYSTEM FOR FECAL AND INGESTA DETECTION ON POULTRY CARCASSES

A multispectral imaging system, including a common aperture camera with three optical trim filters (515.4, 566.4 and 631 nm), which were selected by visible/near‐infrared NIR spectroscopy and validated by a hyperspectral imaging system, was developed for a real‐time, on‐line poultry inspection application. The algorithm developed by a hyperspectral imaging system was employed for multispectral image analysis to validate the accuracy of fecal and ingesta detection in real‐time poultry processing. A multispectral imaging system could be used effectively for detecting feces (from duodenum, ceca, and colon) and ingesta on the surface of poultry carcasses with the processing time of approximately 251 ms or 3.99 frames/s. The multispectral imaging system developed in this research can be used for real‐time, on‐line detection of fecal and ingesta contaminant on poultry carcasses. The overall accuracy to identify fecal and ingesta contaminants was 96.8% and the prediction accuracy to identify each contaminant were 92.4% for duodenum and 98% for ceca, colon, and ingesta with moderate false positives.     

基于两种化学振荡体系检测奶粉中钙含量

采用硫酸-硫酸铈铵-溴酸钠-溴化钠-丙二酸(体系Ⅰ)和硫酸-硫酸锰-溴酸钠-溴化钠-丙酮(体系Ⅱ)为振荡体系,检测奶粉中固有的钙含量。采用国标检测方法,对奶粉标样中固有的钙含量进行测定,实现对该方法的验证。结果表明,采用体系Ⅰ时,奶粉中钙的总含量在0.0056~0.0174 g范围内,钙的总含量与最大振幅线性关系良好;采用体系Ⅱ时,奶粉中钙的总含量在0.0227~0.0323 g范围内,钙的总含量与波动周期线性关系良好。两种体系奶粉中固有钙含量的检测范围均为0.0030~0.0072 g。比较两个体系,体系Ⅰ一个样本的检测时间为900~1400 s,体系Ⅱ一个样本的检测时间为6000 s,相比较而言,体系Ⅰ优于体系Ⅱ,可缩短样本的检测时间。     

Starch modification using a twin‐roll mixer as a reactor

A starch modification reactor has been established using a HAAKE rheometer incorporating a twin‐roll mixer, which has been modified to improve its sealing and feeding, and to establish an oxygen‐free environmental. The advantages of the system include: (i) starch modification can be carried out at high starch concentration (up to 70%); (ii) combining the steps of starch gelatinization and chemical modification; (iii) controllable reaction time; and (iv) smaller sample size (60 g) requirement. The effects of water content, rpm, time, and temperature on the reactive system was systematically investigated. Corn starch (60% starch concentration) was successfully grafted with acrylamide then crosslinked by N,N′‐methylene‐bisacrylamide to produce biodegradable superabsorbent polymers using this reactor.     

Biological enhancement of tetrachloroethene dissolution and associated microbial community changes

A bench-scale study was performed to evaluate the enhancement of tetrachloroethene (PCE) dissolution from a dense nonaqueous phase liquid (DNAPL) source zone due to reductive dechlorination. The study was conducted in a pair of two-dimensional bench-scale aquifer systems using soil and groundwater from Dover Air Force Base, DE. After establishment of PCE source zones in each aquifer system, one was biostimulated (addition of electron donor) while the other was biostimulated and then bioaugmented with the KB1 dechlorinating culture. Biostimulation resulted in the growth of iron-reducing bacteria (Geobacter) in both systems as a result of the high iron content of the Dover soil. After prolonged electron donor addition methanogenesis dominated, but no dechlorination was observed. Following bioaugmentation of one system, dechlorination to ethene was achieved, coincident with growth of introduced Dehalococcoides and other microbes in the vicinity and downgradient of the PCE DNAPL (detected using DGGE and qPCR). Dechlorination was not detected in the nonbioaugmented system over the course of the study, indicating that the native microbial community, although containing a member of the Dehalococcoides group, was not able to dechlorinate PCE. Over 890 days, 65% of the initial emplaced PCE was removed in the bioaugmented, dechlorinating system, in comparison to 39% removal by dissolution from the nondechlorinating system. The maximum total ethenes concentration (3 mM) in the bioaugmented system occurred approximately 100 days after bioaugmentation, indicating that there was at least a 3-fold enhancement of PCE dissolution atthis time. Removal rates decreased substantially beyond this time, particularly during the last 200 days of the study, when the maximum concentrations of total ethenes were only about 0.5 mM. However, PCE removal rates in the dechlorinating system remained more than twice the removal rates of the nondechlorinating system. The reductions in removal rates over time are attributed to both a shrinking DNAPL source area, and reduced flow through the DNAPL source area due to bioclogging and pore blockage from methane gas generation.     

唾液乳杆菌M18-6在发酵大豆蛋白体系中的应用

通过测定发酵豆乳的凝乳时间、贮藏期间的活菌数和对菌株自身耐受性评价,筛选出1株能够稳定快速发酵大豆蛋白体系的乳酸菌菌株。以最短凝乳时间和贮藏期菌株的高存活率为主要依据,筛选出凝乳时间短、活菌贮藏性稳定的1株唾液乳杆菌M18-6,并对发酵体系进行抗氧化性评价。结果表明:M18-6最佳凝乳时间为(2.50±0.20)h,24 d贮藏期内M18-6菌株活菌数始终保持在10^8 CFU/mL以上,在pH 2.0的酸性环境中,存活率高于3.16×10^8 CFU/mL;同时发现,M18-6发酵体系对DPPH自由基的清除率达到93.34%,显著高于未发酵体系(P<0.05)。筛选出的唾液乳杆菌M18-6凝乳时间短,具有良好的活菌贮藏稳定性和清除DPPH自由基的能力,为后期开发快速发酵大豆蛋白体系的益生菌菌株提供理论依据。     

西瓜品质检测系统的光热环境测试

目的 掌握西瓜品质检测试验台光照箱内部光热环境变化。方法 在西瓜品质检测试验台的光源开启后30 min内, 每隔1 min采集光照箱的温度和光源的光谱。对光照箱的温度变化过程采用一阶系统的阶跃响应过程进行分析, 将光谱分为可见光波段(400~700 nm)和近红外波(700~1100 nm), 通过对其光谱值积分得到其光谱能量, 并对光谱能量随时间变化的情况进行分析。结果 采用一阶系统的阶跃响应公式计算得到各观测时刻的温度计算值与实测值的相关系数为0.9997, 西瓜品质检测试验台光照箱内温度稳定时间小于15 min, 光源的光谱稳定时间小于1 min。结论 西瓜品质检测试验台光照箱温度升高过程为一阶系统的阶跃响应过程, 西瓜品质检测试验台光照箱内光热环境稳定时间不大于15 min, 西瓜品质检测试验可在光源开启15 min之后进行。     

Chemical oxygen demand using closed microwave digestion system

A new approach to determine the chemical oxygen demand (COD) using a closed microwave digestion (CMD) system to replace the conventional, time-consuming open reflux (OR) method is proposed. The procedure uses a laboratory-grade closed microwave digestion system (one magnetron) for the digestion of small volume of samples (3.0 mL) in a completely closed (90 mL) Teflon vessel, digesting 10 samples at a time in the range of COD values of 5-1000 mg L(-1). The digestion time required is 15 min as compared to the 2 h required for the conventional OR method. Chloride ion interference can be removed up to 6000 mg of Cl- ions L(-1) as compared to the 2000 mg of Cl- ions L(-1) removed by conventional OR method. The present work reveals that the filtration of effluent samples by membrane filter or homogenization is not essential to obtain reproducible results. The proposed method is cost-effective; saves time, energy, and reagents with providing precise results for both the pure organic compounds and wastewater samples; and is ecofriendly.     

Effects of the working vacuum level on mechanical milking of buffalo

Mechanized milking has become widely used for buffalos in Italy in recent years, thus improving the management and the productivity of farms. The apparent similarities between buffalo and cattle have often resulted in applying the same milking systems and techniques currently used for dairy cows. Considering the effect of mechanical milking on animal health, productivity, and welfare in intensive livestock farming, this study compares the effects of milking at low vacuum (36 kPa) and medium vacuum (42 kPa) on milk emission characteristics and milking system performance. Individual milk flow curves were registered to analyze milk yield, average flow rate, and milking time, and milking operations were recorded to evaluate the system performances. When using 36 kPa vacuum, a significant increase in milking time and in the lag time before milk ejection occurred, as well as a decrease in average flow rate and residual milk. However, the vacuum level did not influence both milk yield and milk ejection time. As a consequence of decreasing the vacuum level to 36 kPa, the milking system throughput was decreased at most by 5 buffalo/h.     

Short communication: Effects of changing teatcup removal and vacuum settings on milking efficiency of an automatic milking system

The aim of this experiment was to assess strategies to reduce milking time in a pasture-based automatic milking system (AMS). Milking time is an important factor in automatic milking because any reductions in box time can facilitate more milkings per day and hence higher production levels per AMS. This study evaluated 2 end-of-milking criteria treatments (teatcup removal at 30% and 50% of average milk flowrate at the quarter-level), 2 milking system vacuum treatments (static and dynamic, where the milking system vacuum could change during the peak milk flowrate period), and the interaction of these treatment effects on milking time in a Lely Astronaut A4 AMS (Maassluis, the Netherlands). The experiment was carried out at the research facility at Teagasc Moorepark, Cork, Ireland, and used 77 spring-calved cows, which were managed on a grass-based system. Cows were 179 DIM, with an average parity of 3. No significant differences in milk flowrate, milk yield, box time, milking time, or milking interval were found between treatments in this study on cows milked in an AMS on a pasture-based system. Average and peak milk flowrates of 2.15 kg/min and 3.48 kg/min, respectively, were observed during the experiment. Small increases in maximum milk flowrate were detected (+0.09 kg/min) due to the effect of increasing the system vacuum during the peak milk flow period. These small increases in maximum milk flowrate were not sufficient to deliver a significant reduction in milking time or box time. Furthermore, increasing the removal setting from 30% of the average milk flowrate to 50% of the average milk flowrate was not an effective means of reducing box time, because the resultant increase in removal flowrate of 0.12 kg/min was not enough to deliver practical or statistically significant decreases in milking time or box time. Hence, to make significant reductions in milking time, where cows have an average milk flow of 2 kg/min and yield per milking of 10 kg, end-of-milking criteria above 50% of average milk flowrate at the quarter level would be required.     

Metal speciation dynamics and bioavailability: bulk depletion effects

Under conditions of bulk depletion, the speciation and bioavailability of trace metals must be considered at two different time scales: (i) the time scale of the biouptake flux, as determined by diffusion of the bioactive free metal, dissociation of the bioinactive complex species, and the internalization rate; and (ii) the time scale of depletion of the bulk medium. The implications of these two time scales for the speciation dynamics are discussed in terms of experimental conditions. The geometry of the system is taken into accountvia a spherical cellular model. It considers a spherical organism depleting a spherical volume in a nonstirred medium and assumes linear adsorption of the metal atthe biointerface and first-order internalization kinetics. In cases where the rate of biouptake is fully controlled by the internalization step, concentration gradients in the medium are insignificant. Then the biouptake becomes independent of the geometry of the system, and the model has a much simpler solution. Examples of trace metal uptake by microorganisms are analyzed: (i) cobalt uptake by Prochlorococcus in the presence of NTA, under conditions where bulk depletion is the controlling process due to the large number of organisms and high internalization rates, (ii) silver uptake by Chlamydomonas reinhardtii with significant effects of bulk depletion, due to the high internalization rate; (iii) lead uptake by Chlorella vulgaris with pratically negligible bulk depletion due to the low internalization rate of the metal; and (iv) lead uptake by intestinal Caco-2 cells, illustrating the simplification of the bulk depletion model for a system with different geometry where internalization is the rate-controlling step.