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Het gecombineerde proces van magnetronbehandeling en onderdompeling in kokend water is een snelle methode voor de productie van stevige aardappelschijfjes die niet bruin kleuren bij blootstelling aan de lucht

Het meten van biochemische parameters voor het vaststellen van de versheid van schol, tong en haring

Het identificeren van belangrijke geurcomponenten van voedingsmiddelen met behulp van gaschromatografie

Crispness is one of the most important sensory characteristics of crispy bread, because consumers associate crispness with freshness, wholesomeness, and quality. This sensory sensation, however, is lost within a few hours after baking, because of a fast water uptake of the crust. Therefore, the aim of this thesis was to systematically determine the mechanisms that lead to the fast loss of crispness and to reveal the parameters that are key for crispness retention. We showed that the crust acts as a barrier for water migration, causing water accumulation in the crust. Reducing this barrier property by increasing the water vapor permeability of the crust to an optimal value of 8 × 10–9 g/(m s Pa) resulted in breads with crispness retention that was more than eight times longer. These breads had either channels or cracks in their crust. Despite the changes of the crust properties, these breads had similar crumb softness retention compared to standard breads. The properties of the crumb also affected the water uptake of the crust, but less so than the properties of the crust. Bread containing a crumb with a lower water vapor permeability had a significantly longer crispness retention. Based on these findings, we propose a model that provides a comprehensive view of crispness loss and concluded that the increase in crust permeability is the best way to create breads with a noticeably longer crispness retention.

Crispness is one of the most important sensory characteristics of crispy bread, because consumers associate crispness with freshness, wholesomeness, and quality. This sensory sensation, however, is lost within a few hours after baking, because of a fast water uptake of the crust. Therefore, the aim of this thesis was to systematically determine the mechanisms that lead to the fast loss of crispness and to reveal the parameters that are key for crispness retention. We showed that the crust acts as a barrier for water migration, causing water accumulation in the crust. Reducing this barrier property by increasing the water vapor permeability of the crust to an optimal value of 8 × 10–9 g/(m s Pa) resulted in breads with crispness retention that was more than eight times longer. These breads had either channels or cracks in their crust. Despite the changes of the crust properties, these breads had similar crumb softness retention compared to standard breads. The properties of the crumb also affected the water uptake of the crust, but less so than the properties of the crust. Bread containing a crumb with a lower water vapor permeability had a significantly longer crispness retention. Based on these findings, we propose a model that provides a comprehensive view of crispness loss and concluded that the increase in crust permeability is the best way to create breads with a noticeably longer crispness retention.

Hoe is het gesteld met de smaak van tomaten. Resultaten van smaaktest gehouden in Tomato World

Hoe is het gesteld met de smaak van tomaten. Resultaten van smaaktest gehouden in Tomato World

De invloed van deze technologie op vitamines, kleur, smaak en textuur. Enzymen en micro-organismen kunnen geinactiveerd worden, terwijl vitamines, kleur en smaak intact blijven

Within the CRAFT project Turpro water quality was researched to be optimised in the turbot recirculation farming system. Within this task the tank renewal rate was varied and growth of turbot was monitored. Within this experiment the question was whether the tank renewal rate affected the eating quality or off-flavour of the fillets.

Within the CRAFT project Turpro water quality was researched to be optimised in the turbot recirculation farming system. Within this task the tank renewal rate was varied and growth of turbot was monitored. Within this experiment the question was whether the tank renewal rate affected the eating quality or off-flavour of the fillets.

Meer aandacht voor de 'innerlijke' kwaliteit van groenten en fruit

Verslag van het in mei gehouden minisymposium te Wageningen. Het werd georganiseerd door de Vereniging voor Voedingsleer en Levensmiddelentechnologie

Verslag van het in mei gehouden minisymposium te Wageningen. Het werd georganiseerd door de Vereniging voor Voedingsleer en Levensmiddelentechnologie

De invloed van deze technologie op vitamines, kleur, smaak en textuur. Enzymen en micro-organismen kunnen geinactiveerd worden, terwijl vitamines, kleur en smaak intact blijven

Het gecombineerde proces van magnetronbehandeling en onderdompeling in kokend water is een snelle methode voor de productie van stevige aardappelschijfjes die niet bruin kleuren bij blootstelling aan de lucht

Het gecombineerde proces van magnetronbehandeling en onderdompeling in kokend water is een snelle methode voor de productie van stevige aardappelschijfjes die niet bruin kleuren bij blootstelling aan de lucht

De invloed van deze technologie op vitamines, kleur, smaak en textuur. Enzymen en micro-organismen kunnen geinactiveerd worden, terwijl vitamines, kleur en smaak intact blijven

The 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 showedα-amylase in bell peppers. Release in French beans was generally increased byα-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.

Het identificeren van belangrijke geurcomponenten van voedingsmiddelen met behulp van gaschromatografie

Fruits 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 340μM 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.

Het meten van biochemische parameters voor het vaststellen van de versheid van schol, tong en haring

The 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 showedα-amylase in bell peppers. Release in French beans was generally increased byα-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.

Meer aandacht voor de 'innerlijke' kwaliteit van groenten en fruit

Het meten van biochemische parameters voor het vaststellen van de versheid van schol, tong en haring

Meer aandacht voor de 'innerlijke' kwaliteit van groenten en fruit

Het identificeren van belangrijke geurcomponenten van voedingsmiddelen met behulp van gaschromatografie

Fruits 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 340μM 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.

In deel 1 over dit onderwerp is ingegaan op de overeenkomsten en verschillen tussen de twee genoemde benaderingen. Deel 2 gaat over de mogelijkheden en voordelen, alsmede over de problemen bij integratie. De literatuurverwijzingen zijn een selectie van een uitgebreide lijst. Deze kan worden aangevraagd bij dr. ir. H.N.J. Schifferstein, Vakgroep Marktkunde en Marktonderzoek, Sectie Sensorisch Onderzoek, Bomenweg 2, 6703 HD Wageningen, tel. 08370-83243

Verslag van het in mei gehouden minisymposium te Wageningen. Het werd georganiseerd door de Vereniging voor Voedingsleer en Levensmiddelentechnologie

Op verzoek van de Consumentenbond zijn in januari 1991 31 monsters bier chemisch en sensorisch onderzocht. Het chemisch onderzoek betrof bepalingen van SO2, nitraat, alcohol, eiwitten, koolhydraten en as. Tevens is de energie-waarde van de bieren berekend. Het sensorisch onderzoek bestond uit een vooronderzoek met de Free Choice Profiling methode om na te gaan welke termen relevant zijn in het beschrijven van verschillen tussen de bieren. Met deze termen zijn alle bieren door het panel beschreven. Een derde sensorisch onderzoek betrof de vraag of blind geteste monsters gemakkelijk binnen een categorie te plaatsen zijn.

Op verzoek van de Consumentenbond zijn in januari 1991 31 monsters bier chemisch en sensorisch onderzocht. Het chemisch onderzoek betrof bepalingen van SO2, nitraat, alcohol, eiwitten, koolhydraten en as. Tevens is de energie-waarde van de bieren berekend. Het sensorisch onderzoek bestond uit een vooronderzoek met de Free Choice Profiling methode om na te gaan welke termen relevant zijn in het beschrijven van verschillen tussen de bieren. Met deze termen zijn alle bieren door het panel beschreven. Een derde sensorisch onderzoek betrof de vraag of blind geteste monsters gemakkelijk binnen een categorie te plaatsen zijn.

Op verzoek van de Consumentenbond zijn in mei 1990 twintig merken koffie, waaronder zes gangbare, elf met een Max Havelaar keurmerk en drie merken van het type Max Havelaar zonder keurmerk, onderzocht op sensorische verschillen. Vijf merken koffie zijn cafeïnevrij. Het sensorische onderzoek is in twee gedeelten uitgevoerd. In het vooronderzoek is nagegaan welke termen relevant zijn in het benoemen van verschillen tussen de monsters. In het hoofdonderzoek zijn alle monsters met een schaalmethode met de in het vooronderzoek gevonden termen beoordeeld. Uit de resultaten blijkt dat er significante verschillen tussen de monsters bestaan bij de aspekten 'aromatisch/vol' , 'verbrand' en ' afwijkend' (karton/papier/teer e.d.). De koffiemerken met het Max Havelaar keurmerk zijn als het meest 'aromatisch/vol' beoordeeld, gevolgd door de gangbare merken. De merken van het type Max Havelaar zonder keurmerk zijn het minst 'aromatisch/vol' gevonden. De cafeïnevrije koffie met een Max Havelaar keurmerk is wat zuurder gevonden dan de overige koffiemerken. De cafeïnevrije koffies zonder keurmerk zijn als meer 'afwijkend' (karton/papier/teer e.d.) beoordeeld dan de overige merken.

Op verzoek van de Consumentenbond zijn in mei 1990 twintig merken koffie, waaronder zes gangbare, elf met een Max Havelaar keurmerk en drie merken van het type Max Havelaar zonder keurmerk, onderzocht op sensorische verschillen. Vijf merken koffie zijn cafeïnevrij. Het sensorische onderzoek is in twee gedeelten uitgevoerd. In het vooronderzoek is nagegaan welke termen relevant zijn in het benoemen van verschillen tussen de monsters. In het hoofdonderzoek zijn alle monsters met een schaalmethode met de in het vooronderzoek gevonden termen beoordeeld. Uit de resultaten blijkt dat er significante verschillen tussen de monsters bestaan bij de aspekten 'aromatisch/vol' , 'verbrand' en ' afwijkend' (karton/papier/teer e.d.). De koffiemerken met het Max Havelaar keurmerk zijn als het meest 'aromatisch/vol' beoordeeld, gevolgd door de gangbare merken. De merken van het type Max Havelaar zonder keurmerk zijn het minst 'aromatisch/vol' gevonden. De cafeïnevrije koffie met een Max Havelaar keurmerk is wat zuurder gevonden dan de overige koffiemerken. De cafeïnevrije koffies zonder keurmerk zijn als meer 'afwijkend' (karton/papier/teer e.d.) beoordeeld dan de overige merken.

Op verzoek van de Consumentenbond zijn zevenentwintig monsters kaas en drie monsters kaasachtigen onderzocht. De monsters zijn op de volgende parameters onderzocht: vocht-, vet-, zout-, nitraat-, nitriet- en natamycine-gehalte, vetzuursamenstelling, sterolgehalte en sensorische eigenschappen. De dieetkazen zijn tevens onderzocht op het natrium- en kaliumgehalte.

Op verzoek van de Consumentenbond zijn zevenentwintig monsters kaas en drie monsters kaasachtigen onderzocht. De monsters zijn op de volgende parameters onderzocht: vocht-, vet-, zout-, nitraat-, nitriet- en natamycine-gehalte, vetzuursamenstelling, sterolgehalte en sensorische eigenschappen. De dieetkazen zijn tevens onderzocht op het natrium- en kaliumgehalte.

Op verzoek van de Consumentenbond zijn 32 merken sinaasappelvruchtenlimonade en limonade met vruchtenextract (sinas) en 13 merken zwarte bessenvruchtenlimonade en limonade met vruchtenextract (cassis) sensorisch onderzocht. Eerst zijn in twee vooronderzoeken met respectievelijk acht monsters sinas en zes monsters cassis bepaald welke termen relevant zijn in het benoemen van de verschillen tussen de merken. Dit is met behulp van de free choice profiling methode en een procrustus-analyse uitgevoerd. Daarna zijn alle monsters sinas en cassis met deze termen beoordeeld.

In overleg met de Consumentenbond zijn de groentesoepen onderzocht op het gehalte aan natrium en glutaminezuur. Verder is de samenstelling van de monsters microscopisch onderzocht op zichtbare en onderscheidbare bestanddelen. Tenslotte zijn verschillen in geur, smaak en mondgevoel tussen de monsters groentesoep in kaart gebracht en zijn de monsters door een sensorisch-analytisch panel op basis van deze verschillen geprofileerd.

Op verzoek van Konsumenten Kontakt zijn veertien monsters bier onderzocht. De monsters zijn onderverdeeld in acht monsters alcoholarm of alcoholvrij bier, drie monsters dry bier en drie monsters gewone pils. De monsters zijn getest op sensorische verschillen. De monsters zijn verder chemisch onderzocht op alcoholgehalte, stamwortgehalte, percentage glucose en percentage malto-dextrine. Alle monsters voldoen aan de eisen van de Warenwet.

Op verzoek van de Consumentenbond zijn 32 merken sinaasappelvruchtenlimonade en limonade met vruchtenextract (sinas) en 13 merken zwarte bessenvruchtenlimonade en limonade met vruchtenextract (cassis) sensorisch onderzocht. Eerst zijn in twee vooronderzoeken met respectievelijk acht monsters sinas en zes monsters cassis bepaald welke termen relevant zijn in het benoemen van de verschillen tussen de merken. Dit is met behulp van de free choice profiling methode en een procrustus-analyse uitgevoerd. Daarna zijn alle monsters sinas en cassis met deze termen beoordeeld.

Op verzoek van Konsumenten Kontakt zijn veertien monsters bier onderzocht. De monsters zijn onderverdeeld in acht monsters alcoholarm of alcoholvrij bier, drie monsters dry bier en drie monsters gewone pils. De monsters zijn getest op sensorische verschillen. De monsters zijn verder chemisch onderzocht op alcoholgehalte, stamwortgehalte, percentage glucose en percentage malto-dextrine. Alle monsters voldoen aan de eisen van de Warenwet.

Het onderzoek naar het waarnemen van voedingsmiddelen is onder te verdelen in twee hoofdrichtingen. Eén richting wordt het analytisch-sensorisch onderzoek genoemd. De tweede richting is het emotioneel-sensorisch onderzoek. Hierbij worden produktvoorkeuren onderzocht door produkten in thuissituatie's te laten beoordelen.

Er zijn 20 monsters zuurkool onderzocht op de volgende aspekten: nettogewicht, uitlekgewicht, zout, zuur, alkohol en sensorische eigenschappen.

Het onderzoek naar het waarnemen van voedingsmiddelen is onder te verdelen in twee hoofdrichtingen. Eén richting wordt het analytisch-sensorisch onderzoek genoemd. De tweede richting is het emotioneel-sensorisch onderzoek. Hierbij worden produktvoorkeuren onderzocht door produkten in thuissituatie's te laten beoordelen.

Zes monsters erwtensoep uit blik zijn onderzocht op het gehalte aan keukenzout en glutaminezuur. Tevens is een procentuele schatting gemaakt van de zichtbare hoeveelheid erwten, vlees en groenten.

Er zijn 24 monsters doperwten en 19 monsters doperwten en wortelen onderzocht op netto inhoud, uitlekgewicht, sortering en uiterlijke kwaliteit, zout, alkohol onoplosbare stof (uitsluitend bij de monsters doperwten) en sensorische aspekten. Het betreft monsters in blik, in glas en diepvries.

Doel van dit onderzoek is: onderzoek naar de mogelijheden om de sensorisch waar te nemen rulheid van appelmoes te kwantificeren met behulp van een objectieve meetmethode.