SENSORY AND INSTRUMENTAL EVALUATIONS OF TEXTURE IN CHEESES MADE FROM OVINE MILKS WITH DIFFERING FAT CONTENTS

The present study considers the influence of reducing the fat content of ovine milk on the sensory and instrumental texture characteristics of the resulting cheeses. Three manufacturing runs were performed. In each run three cheese batches were manufactured using milks with differing percentage fat contents (8%, 4%, and 2% fat). Analysis of cheese samples was performed at 60, 90, and 120 days of ripening.
The instrumental method used to evaluate cheese texture was uniaxial compression at constant speed, taking readings of stress, strain, and modulus of elasticity (E). Statisticalanalysis revealed differences forboth the differentfat contents and the ripening times considered. Instrumental parameter values increased with lower cheese fat contents; with a 20% reduction in the fat to dry matter content from full-fat to reduced-fat cheeses, resulting in a 35% increase in maximum stress and in the slope of the stress-strain curve at the end of ripening. The greatest sensory differences between samples were recorded for firmness.     

SENSORY EVALUATION OF CHEDDAR CHEESE MADE WITH SODIUM CHLORIDE OR MIXTURES OF SODIUM AND POTASSIUM CHLORIDE

Cheddar cheese (three trials) was made from split lots of curd, salted with NaCl or mixtures of NaCl/KCl and ripened at 3 ± 1C. Preferences for cheese, as determined by consumer panels, were significantly (P < 0.05) affected by flavor and order of presentation to panelists but not (P > 0.05) by age of cheese. In the first order of presentation, cheese made with NaCl was preferred over those made with NaCl/KCl, whereas in the second order of presentation cheese made with 1.52% NaCl/KCl (2:1) was preferred. In the third order of presentation, cheese made with 1.72% NaCl (rather than 1.5%) was preferred. Overall, mean scores were higher for cheeses made with NaCl than with NaCl/KCl. However, the score of cheese made with ca. 1.5% NaCl/KCl was not significantly (P > 0.05) different from that of cheese made with ca. 1.5% NaCl. Cheese made with ca. 1.5% NaCl/KCl (2:1) was consistently preferred over cheeses containing more KCl.     

CHANGES IN CHEMICAL, SENSORY AND RHEOLOGICAL CHARACTERISTICS OF MANCHEGO CHEESES DURING RIPENING

Manchego cheese is a high-fat pressed ewe's-milk cheese made in Castilla-La Mancha (Spain) and produced by enzymatic coagulation. The minimum ripening time before marketing required by the Regulatory Board of the Manchego Cheese Appellation of Origin is 60 days.
This paper describes the physicochemical, proteolysis, sensory and texture characteristics of Manchego cheese, and the degree of homogeneity of cheeses made under the Manchego Appellation of Origin. The data gathered in this study indicate that sensory and instrumental analysis are useful tools for detecting changes in Manchego cheese during ripening. These changes were first detected by the instrumental analysis (2 months). The panelists detected differences after 4 months' ripening in all the factories. With physicochemical analysis, on the other hand, longer ripening times (6–8 months) are required before such changes become appreciated.     

PERCEPTION OF FAT IN A MILK MODEL SYSTEM USING MULTIDIMENSIONAL SCALING

This study examined the contributions of stimulus fat content and flavor volatiles to the perception of fat in a milk model system. The model system was formulated by adding bland vegetable oil (0%, 5%, or 10% w/v) and natural cream flavor (0%, 0.5% or 1% w/v) to a skim milk base. Panelists judged pairs of samples for similarity on the basis of three attributes (fat content, mouthcoating and thickness) and the results were analyzed using a multidimensional scaling procedure. Two-dimensional solutions best represented the data. The stimulus spaces for fat content and mouthcoating were visually similar to each other and provided reasonable separation of the samples. Instrumental measures helped to define the underlying dimensions of the stimulus space for fat content. Dimension 1 related to texture and included the contributions of viscosity, and fat particle size and number distribution; dimension 2 related to flavor perception. The sample with a moderate fat content (5%) and the highest concentration of added cream flavor (1%) was perceived to be similar to the 10% fat samples with added flavor. Thus, the added flavor provided the sensation of higher fat content. These data suggest that flavor plays an important role in the preception of fat in dairy foods. A psychophysical model of fat perception in dairy foods is proposed which includes the contribution of viscosity, fat particle size and number distribution, and volatile flavor perceptions.     

白鱀豚和江豚体内几种金属元素和有机氯的研究

本文报道了白鱀豚和江豚体内7种金属元素的组织分布以及有机氯(多氯联苯、六氯苯,滴滴涕)含量方面的研究,为两种动物的保护提出一个值得注意的问题。     

酒花浸膏及其异构化衍生物抗食品腐败菌的初步研究

以啤酒花及其异构化衍生物为原料,从中初筛出两种最有效抗菌成分β-酸和六氢β-酸,并测定其对几种常见食品腐败菌的抑制作用和最低抑菌浓度,结果表明β-酸(20×10-6)、六氢β-酸(8×10-6)对肉制品中的主要污染菌--李斯特菌有抑制作用,对荧光假单孢菌、普通变形杆菌也有较明显的抑制效果.     

SENSORY CHARACTERISTICS OF POTASSIUM LACTATE AND SODIUM CHLORIDE IN A MODEL SYSTEM

The objective of this study was to assess the sensory characteristics of potassium lactate (PL) in combination with salt (NaCl) in a model system at common usage levels for meat systems. Using a gelatin-based (3%) model system containing various concentrations of potassium lactate (0%, 1%, 2%, and 3%) and sodium chloride (0%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3%), a sensory panel (10) selected for salt sensitivity (0.08% threshold or less) scored the intensity of saltiness and bitterness of each treatment combination using a scale of 0 = none and 15 = intense. As salt concentration increased, saltiness increased and bitterness decreased; as PL increased, saltiness and bitterness increased. At 2% salt, the bitterness of PL was masked; however, salt concentrations below and above 2% were less effective in bitterness reduction.     

EFFECT OF HOMOGENIZATION AND FAT CONTENT ON ORAL PERCEPTION OF LOW AND HIGH VISCOSITY MODEL CREAMS

Assessed under low-intensity red illumination, homogenized and thickened higher fat milk samples evoked higher sensory ratings of creaminess than did the unhomogenized or lower-fat milks that had not been thickened to the viscosity of double cream. Furthermore, perceptual ratings of fat content showed the same dependency on homogenization, higher fat and thickness and were entirely accounted for by the creaminess ratings. This indicates that assessors recognize the type of milk or cream most similar to a rated standard and infer its fat content on the basis of tactile patterns produced in the mouth by forces at the surface of small and even-sized dairy fat globules when bulk forces are produced by sufficient viscosity.     

慢性颞叶癫痫大鼠行为、电图发作和核磁共振研究--海马-内嗅皮质-颞叶新皮质通路

目的和方法：强直电刺激（６０Ｈｚ,０．４￣０．６ｍＡ,２ｓ）左、右侧背侧海马或中部颞叶新皮质制作慢性大鼠癫痫模型,观察大鼠行为、ＥＥＧ、深部电图以及各脑区Ｔ２（质子横向驰豫时间）加权核磁共振成象（Ｔ２－ＭＲＩ）结构改变,研究海马－内嗅皮质－颞叶新皮质、大脑皮层神经通路在诱发颞叶癫痫中的可能作用。结果：右侧海马刺激组的原发性、继发性湿狗样抖动及癫痫“点燃”效应的发生率明显高于左海马和左、右颞叶新皮质     

STUDIES ON THE METABOLISM OF UREA AND OTHER NITROGENOUS COMPOUNDS IN CHLORELLA ELLIPSOIDEA: III ASSIMILATION OF UREA

Assimilation of urea by Chlorella ellipsoidea was investigatedby using ¹⁴C-urea. It was revealed that urea carbon metabolizedby the N-starved cell was almost quantitatively recovered incarbon dioxide under dark-aerobic conditions. The rate of ureaconsumption was considerably influenced by the N-content ofalgal cells, practically no metabolism of urea being observedwith the cells containing more than 7 per cent N on a dry weightbasis. Similar results were also obtained when urea was replacedwith ammonia as nitrogen source. Based on the results obtained,a tentative scheme for the assimilation process of urea in Chlorellawas proposed. (Received February 7, 1960; )     

肇庆星湖浮游植物状况及其富营养化评价

研究了 1 996年 4月至 1 997年 7月肇庆星湖 5个子湖泊浮游植物种类和数量变化。在 1 996年 4月至 1 997年 7月 6次采样中 ,共鉴定出浮游植物 82种 ,其中绿藻门 37种 ,其次为硅藻和蓝藻门 ,优势种有鼓藻、栅藻、衣藻、席藻、直链藻、多甲藻和裸藻等。大多数采样点年平均浮游植物密度为 1 0 4 个 /L至 1 0 5个 /L,整个湖泊年平均密度为 4.2 8× 1 0 5个 /L。星湖各子湖泊全年的总氮、总磷含量分别低于 1 mg/L和 0 .1 mg/L ,以叶绿素 a、总氮、总磷、氨氮、COD和 BOD为参数的营养状态指数 (TLI) ,除波海湖外均小于 50。根据浮游植物种类和密度及综合营养状态指数评价结果 ,星湖的富营养化状况属于中营养化至富营养化之间 ,其中波海湖已达到富营养化水平 ,5个湖泊的富营养化程度由高至低依次为 :波海湖、仙女湖、里湖、青莲湖、中心湖。     

在不稳定和相对稳定培养体系中CFU-S生长的动力学观察

利用 Dexter 培养方法,我们在体外对小鼠胎肝进行了长期液体培养。根据换液后悬液细胞总数的不同,建立了不稳定和相对稳定两个培养体系,并利用12d 脾结节检测和单个脾结节转移技术,观察了体系中悬液细胞总数,CFU-S 数及其自我更新的动态变化。表明在不稳定培养体系中,悬液细胞总数和 CFU-S 数增长较快,但由于每周换液时悬液细胞的丢失,可能使体系长时间处于应激状态,其自我更新力衰减也较快。而在相对稳定体系中,由于换液时其悬液细胞的再次种入,使总数保持相对恒定,CFU-S 数的变化比较平缓,其自我更新力的衰减也相对缓慢。提示在造血细胞体外液体培养体系中存在着一种生理性反馈调节活动,但其机理有待进一步研究。     

INSTRUMENTAL AND SENSORY EVALUATION OF TEXTURAL ATTRIBUTES IN CHEESE ANALOGS: A CORRELATION STUDY

The objective of this study was to investigate the usefulness of an array of statistical techniques to describe relationships between instrumental data and non‐oral sensory texture profiling scores by using a range of model processed cheese analogs as example. Pairwise correlation, used as an exploratory tool, showed no significant correlation for flexibility and greasiness with any individual instrumental parameter. Stepwise regression, principal component regression and partial least squares regression were used to generate models for firmness, stickiness and curdiness of the analogs studied. No models could be generated for flexibility and greasiness, and models for rubberiness had poor quality of fit compared with the other sensory attributes. In general, firmness, stickiness and curdiness were satisfactorily modeled by using chemical data and small deformation rheological parameters. Compression data (large deformation), often used in correlation studies regarding the texture of cheese, did not necessarily lead to better correlation results in comparison with other instrumental parameters used in this research.