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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Studies on the low temperature infrared heat processing of soybeans and maize
No full textA modified process for the infrared heat processing of oilseeds and cereal grains at relatively low temperatures is put forward. The process which involves an additional holding step and potentials for saving energy was investigated on a pilot plant on the basis of which a design is proposed for industrial applications. The process was used in order to produce full-fat soy flour and maize germ with long shelf life and improved nutritive and organoleptic qualities. Antitrypsin factors, lipoxygenase and lipase could be inactivated with no damage to available lysine. Overheating not only caused damage to available lysine but also made the products more prone to rancidity possibly by causing destruction of natural antioxidants. The process caused protein solubility and dispersibility to fall and starch (in maize germ) to gelatinize. Water absorption of maize germ also increased. In soybeans, urease was found to be a good indicator of the extent of inactivation of antitrypsin factors, while lipoxygenase was found more heat sensitive than urease and antitrypsin factors. For evaluating storage stability, in addition to measuring peroxide value and % free fatty acids, sensory analysis was also carried out.The process was further applied for treating soybeans prior to oil extraction. It was concluded that the quality of the crude oil obtained from the pretreated beans in terms of oxidation products, free fatty acids and nonhydratable phospholipids was such that the alkali treatment step in the refining process could be circumvented. The improved quality of the crude oil was attributed to the inactivation of phospholipase D, lipoxygenase and lipase. The residual defatted flakes showed low levels of trypsin inhibitor activity and could be used directly as food or feed.Finally, the involvement of phospholipase D in the hydrolysis of phospholipids and formation of nonhydratable phospholipids in soybeans was elucidated by radio(chemical) methods, as well as thin layer chromatography and densitometry. The presence of an active, soluble form of the enzyme with isoelectric point 4.8 was shown by isoelectric focusing.</p
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Flavour release from dried vegetables
No full textThe research described in this thesis was focused on the development of an in vitro model system for isolation of volatile compounds from dried vegetables under mouth conditions, such as volume of the mouth, temperature, salivation and mastication. Instrumental analysis of these volatile compounds by gas chromatography (GC), combined with mass spectrometry, flame ionisation detection (FID) and sniffing port detection (SP) was correlated with descriptive sensory analysis. Dried vegetables were subjected to these techniques in order to study three aspects. (1) Factors influencing flavour release from dried vegetables under mouth conditions. (2) Suitability of three types of the model system for simulation of flavour release in the mouth. (3) Characterisation of the flavours of rehydrated vegetables, as influenced by cultivar, origin, storage and rehydration conditions.Flavour perception, physical aspects of flavour release, flavour analysis and factors affecting the flavour of dried vegetables, including literature concerned were discussed briefly in Chapter 1 . The thesis was outlined at the end of this chapter.Three types of the mouth model system were introduced in Chapter 2 and compared for flavour release from rehydrated bell peppers. Release was largest in the 'purge-and-trap1system, followed by the 'dynamic headspace and mastication, (DHM) and dynamic headspace' system, respectively.Flavour release influenced by the composition of artificial saliva was studied for bell peppers in Chapter 3 and for French beans in Chapter 4 . Influence of saliva volume on the flavour release from French beans was studied in Chapter 4 as well. Saliva component mucin mainly decreased flavour release in both vegetables, because of flavour~ protein interactions, a similar effect showed α-amylase in bell peppers. Release in French beans was generally increased by α-amylase, probably due to degradation of inclusion complexes of starch. Decrease in flavour release from French beans by saliva volume was evaluated in a model study. GC/SP patterns of odour active compounds were hardly influenced by both saliva composition and volume.Chapter 5 revealed that flavour release from rehydrated French beans, red bell peppers and leeks in the DHM model system did not differ significantly from their release in the mouth of 12 assessors. These assessors released volatile compounds with different efficiencies, but they showed a statistically consistent efficiency in flavour release across the vegetables.The flavours of the three rehydrated vegetables mentioned above were characterised by GC/SP of volatile compounds released in the DHM model system and by descriptive sensory analysis (Chapter 6). A common odour profile was shown in the vegetables, comprising each of the odour active compounds present in French beans. correlation of rehydrated vegetables with sensory attributes and volatile compounds showed considerable contribution of volatile compounds to the flavour of rehydrated vegetables.The flavours of commercially dried bell peppers (origins Chile, Hungary and Turkey) were evaluated by GC/SP and descriptive and hedonic panels ( Chapter 7 ). Although the three origins differed substantially in FID patterns, GC/SP patterns and scores for 'odour' attributes in sensory analysis were hardly different. Differences in appreciation between Chilean and Turkish bell peppers are therefore expected to be due to differences in 'taste' attributes (sour, bitter, sharp and pungent).The influence of storage conditions (water activity (aw), temperature and light) on the flavour of dried French beans was studied in Chapter 8 . Elevated temperature at aw 0.3 and 0.5 resulted in an increase in the number of assessors perceiving chemical, rotten odours in GC/SP and in an increase in scores for 'chemical', 'burned', 'musty' and ,bitter, attributes in sensory analysis. Light exposure at aw 0.1 resulted in an increase in the number of assessors perceiving chemical odours at the sniffing port and in increased scores for 'chemical, and 'burned' attributes in sensory analysis. French beans stored at 200C were more appreciated by the hedonic panel than those stored at 400C (absence of light, aw 0.3). Relationships between differently stored French beans, sensory attributes and volatile compounds indicated the latter compounds to be responsible for the difference in flavour and appreciation of dried French beans by storage conditions.The flavour of French beans influenced by rehydration conditions was described in Chapter 9 . Extended rehydration resulted in GC/SP in increased intensity for 2-butenal, 2methyl -2 -butenal, 1-octen-3-one and one unknown compound and in increased intensities for chemical,, 'mealy', ,mushroom, and musty, attributes in sensory analysis. Both instrumental and sensory analysis of the texture revealed a gradual decrease with extended rehydration. Relationships between sensory attributes and volatile compounds showed major contribution of volatile compounds to the difference in flavour of French beans resulting from rehydration conditions.It can be concluded ( Chapter 10 ) that flavour release from rehydrated vegetables was influenced by both saliva composition and volume. Mouth model system DHM simulated flavour release in the mouth quite well. The flavours of dried vegetables were shown to be influenced by cultivar, origin, storage and rehydration conditions.</TT
Characterisation of the flavour of fresh bell peppers (Capsicum annuum) and its changes after hot-air drying : an instrumental and sensory evaluation
No full textFruits of Capsicum annuum and C. frutescens are commonly used in the diet because of their typical colour, pungency, taste. and distinct aroma. The fruits are eaten fresh or processed, as unripe (green) or ripe (e.g., red, yellow, orange, white) peppers. In the last decade. attention is shifting towards flavour as an important quality parameter for fruits and vegetables. The flavour of fruits and vegetables, as perceived during consumption, is the overall sensation provided by the interaction of taste, odour, mouth feel, sight, and sound. The composition of non-volatile compounds influences mainly the sensory perceived taste, while the aroma is affected by volatile compounds.In this thesis, the flavour, including taste, aroma, non-volatile and volatile compounds, of fresh and dried bell peppers were evaluated. The major Dutch bell pepper cultivar for export, i.e., C. annuum cv. Mazurka, was used as basic cultivar throughout the thesis, others were included for comparison of results.Instrumental and sensory flavour evaluation of fresh bell peppersDevelopment of non-volatile bell pepper compounds . In chapter 2, some growth characteristics and changes in compositions of non-volatile compounds (sugars, organic acids) during ripening of cv. Mazurka and cv. Evident were investigated. The development of the fruits showed a growth (between 4-7 weeks after fruit set) and ripening phase (7-10 weeks). During growth, fresh weight increased rapidly, while during ripening the colour turned from green to red, which was reflected in a decreased level of chlorophyll a (i.e., green pigments) and an increased level of carotenoids (i.e., orange/red pigments). Two high performance liquid chromatography (HPLC) methods were developed for the analysis of sugars and organic acids in bell peppers. The sugars detected were, sucrose, glucose, and fructose, and the major organic acids detected were ascorbic, citric and malic acid, while oxalic, fumaric, shikimic, and pyroglutamic: acid were present at lower concentrations. The levels of sugars and organic acids showed distinct ripening related patterns, i.e., glucose, fructose, citric and ascorbic acid increased while sucrose and malic acid decreased.Relationships between non-volatile compounds and taste . Based on these time series, three distinct ripening stages (i.e., green, turning, and red) of cv. Mazurka and cv. Evident were selected for instrumental and sensory evaluation, in Chapter 3. The composition of sugars and organic acids were analysed and the fruits were evaluated by a sensory descriptive panel on flavour attributes, perceived while eating. The flavour of green bell peppers was characterised by bitter taste and grassy, green bell pepper, and cucumber aroma, while red bell pepper aroma, sweet and sour taste were typical for the turning and red fruits. The relationships between sugars and sweetness, and organic acids and sourness, and dissociated organic acids and sourness were examined using principal component analysis (PCA). It appeared that sweetness, which was typical for the ripe stages, closely related to glucose, fructose, total sugar, and dry matter content, while sourness, also characteristic for the ripe stages, closely related to total citric and total ascorbic acid. PCA on calculated undissociated and dissociated acids revealed that, mainly undissociated ascorbic acid and citric acid in the "-1" and "-2" dissociation forms related closely with sourness. Based on these results and the available literature, it was suggested that undissociated ascorbic acid might be directly important for the sour perception, while the dissociated forms of citric acid influenced the sourness by increasing the proton (H +) concentration.Development of volatile bell pepper compounds . In chapter 4, the same ripening stages of cv. Mazurka were selected for evaluation of the volatile compounds, for which samples were cut into pieces or completely homogenised. Sixty four compounds were analysed and identified in the headspaces of the different samples by gas chromatography (GC) and GC-mass spectrometry. A trained sniffing port panel detected and characterised 30 odour compounds, of which 21 could be identified. The GC-sniffing profiles of all ripening stages and sample preparations had several odour compounds in common, i.e., 2,3-butanedione (caramel odour), 1-penten-3-one (chemical/pungent, spicy), hexanal (grassy), 3-carene (red bell pepper, rubbery), (Z)-β-ocimene (rancid, sweaty), octanal (fruity), and 2-isobutyl-3-methoxypyrazine (green bell pepper). Furthermore, major ripening and preparation related differences were observed. During ripening from green to red, many volatile compounds having green-related odour notes e.g., (Z)-3-hexenol (grassy, lettuce, cucumber), nonanal (mushroom, herbal), 2-sec-butyl-3-methoxypyrazine (carrot, lettuce, grassy), linalool (floral, green bell pepper), (2)-3-hexenal (grassy, green bell pepper, fruity), and 1-hexanol (fruity, green bell pepper, herbal), decreased or even disappeared. Only the levels of (E)-2-hexenal and (E)-2-hexenol, which have almond, fruity, sweet odours, were higher in the turning and red fruits. Disruption of the cell structure by homogenization of the fruits favoured oxidation of unsaturated fatty acids by lipoxygenase and other enzymes, and stimulated the formation of related alcohols, aldehydes, and ketones; several of these compounds had distinct odour notes.Biochemical aspects of the formation of specific volatile bell pepper compounds . The development and origin of these enzymatic formed volatiles were studied in more detail in Chapter 5. Extracts of green bell peppers of cv. Mazurka were analysed for the presence of lipoxygenase (LOX); a pH-optimum of 5.5-6.0 was obtained and enzyme activity was 100% and 51% inhibited by two specific LOX inhibitors (10 mM of n -propyl gallate and 340 μM of 5,8,11,14-eicosatetraynoic acid). During bell pepper ripening, LOX activity decreased 70% between 6 and 8 weeks after fruit set. The composition of enzymatic formed volatiles showed four typical ripening related patterns. The origin of these compounds was investigated by adding specific LOX substrates to homogenates of green and red bell peppers. Addition of linoleic acid to green homogenates increased significantly the levels of hexanal, hexanol, 2-pentylfuran, (E)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, but also (2)-3-hexenal, whereas addition of linolenic acid to the same homogenates increased the levels of (2)-3-hexenal, (E)-2-hexenal, (Z)-2-hexenal, (Z)-2- pentenal, (E)-2-pentenal, (Z)-2-pentenol, (E)-2-pentenol, and 1-penten-3-one; similar qualitative effects were observed in the red pepper homogenates. A biochemical pathway was proposed for the formation of volatile bell pepper compounds upon tissue disruption based on experimental data and comprehensive literature.Influence of hot-air drying on the instrumental and sensory flavour evaluation of fresh bell peppersEffects of hot-air drying on the composition of non-volatile and volatile flavour compounds. In chapter 6, the composition of non-volatile and volatile odour compounds were analysed before and after drying of four bell peppers with distinct flavours, i.e., green and red cv. Mazurka, white cv. Blondy, and yellow cv. Kelvin. Hot-air drying affected both the composition of non-volatile and volatile compounds. The levels of glucose, fructose, ascorbic, citric, and oxalic acid decreased, while the levels of sucrose, malic, fumaric, and cis-aconitic acid increased. Glucose, fructose, and ascorbic acid possibly participated in the Maillard reaction during heating. The effects of hot-air drying on the composition of volatile bell pepper compounds could be distinguished in three groups i.e., 1) compounds which decreased or disappeared, 2) compounds which increased or were formed, and 3) compounds which showed no clear changes.The first group represented the majority of volatiles, which apparently evaporated during drying. Most of these compounds were partly retained in the dried bell peppers, but some disappeared completely such as, (Z)-2-pentenal, (E)-2-pentenal, (2)-3-hexenal, (Z)- 2-pentenol, (E)-2-pentenol, (E,E)-2,4-hexadienal, and (E,Z)-2,4-hexadienal. The majority of these compounds were ascribed to the enzymatic breakdown of unsaturated fatty acids upon tissue disruption (Chapter 5). Therefore, it was suggested that the disappearance of these compounds was due to heat inactivation of enzymes more than evaporation during drying. Sniffing port evaluation showed that the compounds, which decreased or disappeared after drying, had mainly "fresh" odour notes like lettuce/grassy/green bell pepper ((Z)-3-hexenal), fruity/almond ((E)-2-hexenal), fruity (octanal), lettuce/green bell pepper ((Z)-3-hexenol), and grassy/green bell pepper (Z)-2-hexenal,The second group included compounds which increased or were formed during drying. The increased levels of 4-octen-3-one, (E)-2-heptenal, (E)-2-octenal, (E,Z) and (E,E)-2,4-heptadienal, decanal, and (E)-2-nonenal were possibly due to autoxidation of unsaturated fatty acids. Whereas, the increased levels of 2- methylpropionic and 2- and 3-methylbutyric acid, 2-methylpropanal, and 2- and 3- methylbutanal seemed to be due to Strecker degradation. Sniffing port evaluation showed that the latter three compounds had distinct cacao, sweaty, and spicy odour characteristics.Changes of the aroma profile of fresh bell peppers due to hot-air drying. In chapter 7, the effects of hot-air drying on the fresh aromas of the four different bell peppers were investigated in more detail. The percentage composition of odour active compounds in the fresh and dried samples were analysed, and the fruits were evaluated by a sensory descriptive panel on aroma attributes, as perceived while smelling. On one hand, hot-air drying decreased the intensity scores of several characteristic fresh aroma attributes. For example, in the green and white fruits, mainly "green" attributes like herbal, grassy, green bell pepper, and cucumber decreased after drying. Moreover, the intensity of the aroma attributes fruity/fresh and floral decreased in the green, white, and red but not in the yellow samples. GC-analysis of the odour active compounds showed that the percentage peak areas of (2)-3-hexenal, 2-heptanone, (Z)-2-hexenal, (E)-2-hexenal, hexanol, (Z)-3-hexanol, (E)-2-hexenol, and linalool, which possessed green, vegetable-like, fruity, and floral characteristics, decreased during drying, which may be responsible for the decreased intensity scores of corresponding aroma attributes in the dried samples. On the other hand, hot-air changed the aroma profile. Five extra attributes, i.e., cacao, caramel, nutty, savoury, and dried tomato, were necessary to describe the aroma of the bell pepper samples after drying. The major odour active compounds detected in the dried samples were 2-methylpropanal, 2 and 3-methylbutanal hexanal, and nonanal. Also, the levels of 2,3-butanedione, 2,3-pentanedione, 4-octene-3-one, (E)-2-octenal, and (E)-2-nonenal were significantly higher in the dried bell peppers. Several of these compounds having cacao, spicy, sweaty/rancid, and sweet odour characteristics may contribute to aroma attributes like savoury, sweettsickly, rancid/sweaty, cacao, and caramel, which were characteristic for all dried samples.Modelling the lipid oxidation, Strecker degradation, and Maillard reaction products during hot-air drying of bell peppers . In Chapter 8, the complex behaviour of volatile bell pepper compounds during drying at different time and temperature conditions was described by four distinct kinetic mechanisms.This thesis provided basic knowledge about the flavour of fresh and hot-air dried bell peppers. This knowledge can be used to study effects of, for example, harvest time, growth conditions, sample variation, cultivars, and seasons on the flavour of fresh and/or dried bell peppers. Furthermore, in this thesis a biochemical pathway was proposed for the enzymatic development of bell pepper volatiles, which can be used as basis for detailed studies on the enzymatic formation of bell pepper volatiles. Finally, the complex behaviour of volatile compounds during hot-air drying of bell peppers was described by four different kinetic mechanisms. This kinetic approach may be used to investigate the behaviour of volatiles in other dynamic processes
Psychophysical evaluation of interactive effects between sweeteners and aroma compounds
No full textThe presence of intense sweeteners in a light soft drink influences the preferences for, and the flavour profiles of these drinks to various extents, depending on the aroma and sweeteners present. In this study equisweet mixtures of sweeteners were composed at 10% Sucrose Equivalent Value. The sucrose/maltitol and sucrose/aspartame mixtures were additive, whereas equisweet binary sucrose/Na-cyclamate mixtures and ternary sucrose/aspartame/Na-cyclamate mixtures revealed synergistic effects.The synergy observed for the ternary mixture was a linear combination of the synergy of the binary mixtures. Sensory analysis (quantitative descriptive analysis) of different solutions containing sweetener mixtures and a water soluble orange aroma revealed that aspartame and Na-cyclamate both differed from sucrose on the attributes chemical and aftertaste. The addition of orange aroma levelled out the differences observed between the sweetener solutions.Instrumental analysis revealed that high sucrose concentrations changed the release of the volatile compounds, while Na-cyclamate did not show this effect. Modelling of volatile release showed that the gas/solution partition coefficient and the mass transfer coefficient are the main factors influencing the release.</p
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