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Project
Study of the endogenous structure determining potential of vegetables and fruits in the context of split stream processing.
Dispersed plant-based foods, such as soups, sauces and smoothies, represent a category of ready-to-eat foods which contain one or more fruit and/or vegetable sources. Owing to their convenience next to their perception as natural products, these foods may convince present-day consumers to a higher consumption of fruits and vegetables. In fruits and vegetables, the cell wall polysaccharide pectin is important for tissue structure. Different types of naturally-present pectin-modifying enzymes (i.e.</>, pectinases) affect pectin nanostructure, changing the functional properties (i.e.</>, texture, rheology) of fruit- and vegetable-based products. Among different fruit and vegetable sources, the differences in pectin structure and variation in endogenous pectinases offer opportunities for structuring plant-based foods. Additionally, thermal and high-pressure processing can be used as techniques for (selective) inactivation of the pectinases. In the context of food products comprising multiple fruit- and/or vegetable sources, this natural or process-modified variety ofpectin and pectinases can fully be exploited using split-stream processing. Split-stream processing is a technique in which the individual ingredients, prior to being combined, are individually subjected to a sequence of specific unit operations directed to specific end-product functionalities. The present research work aimed at evaluating the potential of the split-stream processing concept for structuring dispersed plant-based foods consisting of multiple fruit and/or vegetable sources, targetingthe individual pre-treatments of each of the raw materials at (selective) inactivation of pectinases.</>
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As the first step, thepectin structure was investigated for the selected raw materials (i.e.</>, tomato, carrot and broccoli). Subsequently, the presence as well as the thermal and high-pressure stability of selected pectinases in tomato, carrot and broccoli purées was studied. The pectinases pectinmethylesterase, polygalacturonase, β-D-galactosidase and α-L-arabinofuranosidase were selected. Pectinmethylesterase and polygalacturonase affect linear homogalacturonan, the most abundant pectin subdomain. Pectinmethylesterase demethoxylates homogalacturonan, changing the pectin degreeof methoxylation while polygalacturonase depolymerizes homogalacturonan. β-D-galactosidase and α-L-arabinofuranosidase degrade galactose- and arabinose-containing side chain structures of the pectin rhamnogalacturonan I subdomain, respectively. Finally, as a split-stream processing case-study, endogenous tomato pectinases were used to change the consistency of tomato-carrot purées.</>
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The pectin structure of tomato was clearly different from the pectin structures of broccoli and carrot. Tomato pectin showed, in comparison, the broadest range in degree of methoxylation, the highest molar mass, the highest overall linearity and the lowest extent of rhamnogalacturonan I branching. Unlikebroccoli and carrot, tomato thus contains particularly long, linear pectin.</>
Thermal and high-pressure inactivation data were obtained forpectinmethylesterase, β-D-galactosidase and α-L-arabinofuranosidase in broccoli, carrot and tomato purées, and for polygalacturonase in tomato purée. These inactivation data allowed for the identification of processing conditions resulting in specific enzyme populations. By applying a thermal treatment to tomato purée, pectinmethylesterase and polygalacturonase catalytic activities could be largely maintained while β-D-galactosidase was completely inactivated and α-L-arabinofuranosidase activity was largely reduced. High-pressure treatment of tomatopurée allowed for selective inactivation of polygalacturonase, β-D-galactosidase and α-L-arabinofuranosidase, resulting in an endogenous enzyme population exclusively comprising catalytically active pectinmethylesterase. In case of carrot purée, thermal treatment allowed to largely inactivate β-D-galactosidase and α-L-arabinofuranosidasewhile pectinmethylesterase activity was mainly maintained. High-pressure treatment of carrot and broccoli purées could maintain high levels of pectinmethylesterase activity while reducing the β-D-galactosidase and α-L-arabinofuranosidase activity levels considerably.</>
Forthe split-stream processing case-study, raw tomatoes were used as source of pectinases while carrots were thermally pre-treated at two different intensities, i.e.</> blanching and cooking (both inactivating all endogenous pectinases), in order to obtain different levels of thermosolubilized pectin. After mechanical disintegration of tomato and carrot into tomato-carrot purées, stimulation of enzyme action at medium temperature level allowed tomato pectinmethylesterase and polygalacturonase action on both carrot and tomato pectin. Carrot pectin, when present in a purée mix of tomato and blanched carrot, was both solubilized and depolymerized by tomato polygalacturonase while mainly enzymatic depolymerization ofthe thermosolubilized carrot pectin was observed in the tomato-carrot purée containing cooked carrot. The final serum pectin properties were however similar for both types of tomato-carrot purée. Carrot contributed more to the consistency of the purée mix compared to tomato. Stimulatingthe catalytic activity of the tomato pectinases resulted in loss of this contribution, leading to a consistency reduction of the purée mix. This liquefaction of purée was larger for the tomato-carrot purée containing blanched instead of cooked carrots. Based on the obtained results, it is suggested that the liquefying effect is related to solubilization anddegradation of pectin that is counteracted by a reduction in particle size. In this respect, the purée mix containing cooked carrot showed smaller particle sizes than the purée mix containing blanched carrot.</>
</>
The present work showed the potential of split-stream processing for structuring dispersed plant-based foods composed of multiple fruit and/or vegetable sources by the interaction of pectin and pectinases of selectively pre-processed streams of raw materials. This processingprinciple is promising for structuring diverse products within this category towards consumers preferences, making use of the particular set of pectic polysaccharides and pectinases belonging to each of the composing plant sources.</></>
</>
As the first step, thepectin structure was investigated for the selected raw materials (i.e.</>, tomato, carrot and broccoli). Subsequently, the presence as well as the thermal and high-pressure stability of selected pectinases in tomato, carrot and broccoli purées was studied. The pectinases pectinmethylesterase, polygalacturonase, β-D-galactosidase and α-L-arabinofuranosidase were selected. Pectinmethylesterase and polygalacturonase affect linear homogalacturonan, the most abundant pectin subdomain. Pectinmethylesterase demethoxylates homogalacturonan, changing the pectin degreeof methoxylation while polygalacturonase depolymerizes homogalacturonan. β-D-galactosidase and α-L-arabinofuranosidase degrade galactose- and arabinose-containing side chain structures of the pectin rhamnogalacturonan I subdomain, respectively. Finally, as a split-stream processing case-study, endogenous tomato pectinases were used to change the consistency of tomato-carrot purées.</>
</>
The pectin structure of tomato was clearly different from the pectin structures of broccoli and carrot. Tomato pectin showed, in comparison, the broadest range in degree of methoxylation, the highest molar mass, the highest overall linearity and the lowest extent of rhamnogalacturonan I branching. Unlikebroccoli and carrot, tomato thus contains particularly long, linear pectin.</>
Thermal and high-pressure inactivation data were obtained forpectinmethylesterase, β-D-galactosidase and α-L-arabinofuranosidase in broccoli, carrot and tomato purées, and for polygalacturonase in tomato purée. These inactivation data allowed for the identification of processing conditions resulting in specific enzyme populations. By applying a thermal treatment to tomato purée, pectinmethylesterase and polygalacturonase catalytic activities could be largely maintained while β-D-galactosidase was completely inactivated and α-L-arabinofuranosidase activity was largely reduced. High-pressure treatment of tomatopurée allowed for selective inactivation of polygalacturonase, β-D-galactosidase and α-L-arabinofuranosidase, resulting in an endogenous enzyme population exclusively comprising catalytically active pectinmethylesterase. In case of carrot purée, thermal treatment allowed to largely inactivate β-D-galactosidase and α-L-arabinofuranosidasewhile pectinmethylesterase activity was mainly maintained. High-pressure treatment of carrot and broccoli purées could maintain high levels of pectinmethylesterase activity while reducing the β-D-galactosidase and α-L-arabinofuranosidase activity levels considerably.</>
Forthe split-stream processing case-study, raw tomatoes were used as source of pectinases while carrots were thermally pre-treated at two different intensities, i.e.</> blanching and cooking (both inactivating all endogenous pectinases), in order to obtain different levels of thermosolubilized pectin. After mechanical disintegration of tomato and carrot into tomato-carrot purées, stimulation of enzyme action at medium temperature level allowed tomato pectinmethylesterase and polygalacturonase action on both carrot and tomato pectin. Carrot pectin, when present in a purée mix of tomato and blanched carrot, was both solubilized and depolymerized by tomato polygalacturonase while mainly enzymatic depolymerization ofthe thermosolubilized carrot pectin was observed in the tomato-carrot purée containing cooked carrot. The final serum pectin properties were however similar for both types of tomato-carrot purée. Carrot contributed more to the consistency of the purée mix compared to tomato. Stimulatingthe catalytic activity of the tomato pectinases resulted in loss of this contribution, leading to a consistency reduction of the purée mix. This liquefaction of purée was larger for the tomato-carrot purée containing blanched instead of cooked carrots. Based on the obtained results, it is suggested that the liquefying effect is related to solubilization anddegradation of pectin that is counteracted by a reduction in particle size. In this respect, the purée mix containing cooked carrot showed smaller particle sizes than the purée mix containing blanched carrot.</>
</>
The present work showed the potential of split-stream processing for structuring dispersed plant-based foods composed of multiple fruit and/or vegetable sources by the interaction of pectin and pectinases of selectively pre-processed streams of raw materials. This processingprinciple is promising for structuring diverse products within this category towards consumers preferences, making use of the particular set of pectic polysaccharides and pectinases belonging to each of the composing plant sources.</></>
Date:1 Oct 2008 → 25 Feb 2014
Keywords:Processing, Vegetable, Multi-phase product, Fruit, Enzymes, Hemicellulose, Pectin
Disciplines:Other chemical sciences, Nutrition and dietetics, Agricultural animal production, Food sciences and (bio)technology
Project type:PhD project