Variation of Vitamin Concentration and Retention in Canned Snap Beans from Three Processing Plants During Two Years

A statistical evaluation of vitamin status during canning was obtained from samplings of raw, blanched and canned snap beans. With the exception of folic acid retention, it was not possible to distinguish the separate plants. This leads to the expectation that the season averages of vitamins from processing plants obtaining material from the same area would be similar. Retention percentages were lower for thiamin, folic acid and B₆ than for ascorbic, which was lower than for carotene. Raw material was a source of variation. Average concentrations in drained canned beans, dry weight basis were: ascorbic acid, 116 mg/100g; carotene, 22 μg/g; thiamin, 3.4 μg; B₆, 5.3 μg/g; and folic acid, 7.3 μg/g.     

基于Budyko假设的年径流计算方法在湿润地区年径流模拟中的应用

鉴于湿润地区气候和人类活动对径流预报结果的影响,以淠河流域横排头水文站以上的六个子流域为例,基于Budyko假设的五种公式进行了年径流量模拟,对1960~1987、2001~2009年两个时段分别进行率定和检验。结果表明,六个子流域中,只有黄尾河、白莲崖和横排头子流域适用五种公式(NSE平均值±标准差依次为0.677±0.157、0.718±0.147、0.687±0.101);Turc-Pike公式和傅抱璞公式的模拟结果均能接受(NSE平均值±标准差依次为0.681±0.139、0.677±0.141),产生误差的原因在于不同阶段降雨—径流的相关性对模型模拟精度的影响较大(P0.05)。     

THERMAL AND HIGH-PRESSURE STABILITY OF PURIFIED PECTIN METHYLESTERASE FROM PLUMS (PRUNUS DOMESTICA)

Pectin methylesterase (PME) from greengage plums (Prunus domestica) has been extracted and purified using affinity chromatography. Only one band on sodium dodecyl sulfate–polyacrylamide gel electrophoresis was obtained, with an estimated molecular weight of 31 kDa. On isoelectric focusing electrophoresis, two bands with neutral isoelectric points (6.8 and 7.0) were detected. The optimal pH and temperature for plum PME activity were 7.5 and 65C, respectively. A study of purified plum PME thermostability was performed at pH 7.5 and 4.0, indicating a higher thermostability at pH 7.5 than at pH 4.0. A biphasic inactivation behavior was observed for thermal treatments (54–70C), whereas its pressure inactivation could be described by a first‐order kinetic model in a pressure range of 650–800 MPa at 25C. Purified plum PME was found to be relatively stable to thermal and pressure (≤600 MPa) treatments, compared to PME from other fruits.     

THE THERMAL STABILITY OF ASPERGILLUS ORYZAE ALPHA-AMYLASE IN PRESENCE OF SUGARS AND POLYOLS

The aim of this study was to test whether it is possible to estimate the heat stability of Aspergillus oryzae alpha‐amylase (α‐amylase) based on the amount of hydroxyl (OH) groups provided in a buffer solution. The thermal stability of the enzyme in a presence of different sugars (sucrose and trehalose) and polyols (mannitol, sorbitol, lactitol and glycerol) was investigated in the temperature range of 62–68C on a kinetic basis. It was investigated if the protective effect of additional substances was correlated to the number of hydroxyl groups (nOH) provided by each of them (per volume unit of the enzyme solution nOH). All additives showed a protective effect on the enzyme's heat stability, which was strongly dependent on the added compound concentration. Among all stabilizing compounds investigated, sucrose exhibited the largest protective effect. The decimal reduction time of α‐amylase activity increased by 33.9 times when 420 mg/mL of sucrose was added to the environment. When the same concentration of trehalose was used, the D‐value increased by 6.4 times compared to the value in the buffer system. The nOH provided in the enzyme solution could not be related to the D‐values for the enzyme thermal inactivation, meaning that the enzyme heat stability was not dependent on the nOH.     

TORSION ANALYSIS OF FRESH AND AGED CHEESES1

Six cheese varieties encompassing a wide compositional and age range were analyzed fresh and after aging to determine correlations between casein proteolysis products, fat content, moisture content, and torsion results. Shear stress, a measure of the strength of the casein matrix, was dependent on the amount of intact α_sl‐casein. Shear strain, a measure of the cohesiveness of a structure, exhibited a negative correlation with fat content and a positive correlation with moisture content. Shear strain was also correlated with the ratio of moisture to protein, an indication of the interaction between casein particles. Torsion tests provide information on the level of degradation of the casein network in cheese, which can be used by manufacturers to alter storage conditions to optimize the quality of their aged cheese., April 10, 2003     

Evaluation of Performance Measurement Instruments on Their Use for Food Quality Systems

Due to regular challenges of food safety, consumers put high demands on the performance of food quality systems. To deal with these requirements, food manufacturers need effective quality management. Performance of food quality systems can be partly realized by quality assurance systems, such as HACCP (hazard analysis and critical control point), ISO (international organization for standardization), and BRC (british retail consortium). However, it is still unknown to what extent these systems factually contribute to the realization of quality in the wider sense. Therefore, an instrument is needed that measures the effectiveness of quality systems.

This article describes the evaluation of instruments on their suitability for the development of a diagnostic instrument that measures the effectiveness of food quality systems. For this evaluation, perspectives of quality, typical characteristics of agrifood production, quantification, and performance measurement of quality management were studied.

Instruments that measure the performance of both quality management and production quality were identified and evaluated on the basis of the defined criteria. The criteria for the performance of production quality were 6 quality dimensions, i.e., product quality, availability, costs, flexibility, reliability, and service. The criteria for performance of quality management were analyses of the relationships between quality management, context of the organization, and production quality, a normative procedure, validation, applicability, classification, and a process approach. Finally, for the final instrument, the evaluation resulted in an integrated approach i.e., a technomanagerial approach, and 3 suitable instruments i.e., Wageningen Management Approach, Extended Quality Triangle, and the quality concept of Noori and Radford.     

A new method to correlate acoustic spectroscopic microscopy (30 MHz) and light microscopy

A powerful new method is used to investigate the correlation between light microscopic and acoustic properties of biological tissues. Specimens of liver were sectioned into successive slices, 250 μm and 10 μm thick. The thick sections were investigated acoustically, the thin sections by means of light microscopy. Markers that could be detected and located, both optically and acoustically, were used to find and reconstruct corresponding regions in the acoustic and optical sections (2·5 × 2·5 mm). Parameter images were reconstructed from the sections investigated acoustically. The acoustic parameters were attenuation at 30 MHz, the slope of the attenuation spectrum (between 10 and 50 MHz), backscattering at 30 MHz, the slope of the backscattering spectrum (between 10 and 50 MHz) and the local ultrasound velocity. Acoustic images were obtained in the frequency range from 10 to 50 MHz, yielding a lateral resolution of about 50 μm. The sections for light microscopy were stained according to the Goldner trichrome staining technique. The histological composition was determined quantitatively, using digital image segmentation techniques. The percentage of collagen-rich fibrous tissue, luminal structure and interstitial spaces, and the number of nuclei were calculated for regions of 250 × 250 μm. These histological features were correlated with the acoustic parameters obtained from the corresponding regions in adjacent sections. It was thus possible to find the histological components responsible for acoustic parameters.     

Temperature Sensitivity and Pressure Resistance of Mushroom Polyphenoloxidase

Measurements of residual enzyme activity and FTIR-spectroscopy revealed that mushroom polyphenoloxidase is a thermosensitive enzyme readily inactivated by temperatures exceeding 50°C. The enzyme is, however, very pressure stable. At room temperature no enzyme inactivation occurred at pressures up to 6 kbar. FTIR-spectroscopy revealed that a modification in enzyme conformation occurred below 9 kbar. Kinetic studies showed that pressure and temperature did not always act synergistically with respect to enzyme inactivation. FTIR-spectroscopy showed that pressure- or temperature-induced changes were considerably different. Both temperature and pressure-temperature inactivation were only slightly influenced by pH (in the pH-range 5.5–7.5).