Process-structure-function relations of mango pectin: In situ and ex situ enzymatic and chemical pectin functionalization

Fruits and vegetables are acknowledged for their wide range of health benefits such as prevention of chronic disease, and reduction of food intake by increasing the satiety. However they are perishable, often season dependent and for many, cultivation is limited to specific climate and regions. Therefore processing to produce intermediate ingredients such as purée is a common solution to facilitate their consumption, increase their shelf-life and year-round availability. Owing to their convenience next to their perception of year-round available natural products, fruit purées are becoming more and more popular. In fruit and vegetable based products, the cell wall polysaccharide pectin is an important polymeric component partially defining the functional and flow properties of such systems. Mango, accounting for almost 39% of the world’s tropical fruit production (82.2 million tons in 2009), is one of the most popular fruits in western countries (FAO, 2011). Mango purée obtained from fruit disintegration has an extremely high consistency leading to many limitations for further purée processing and manipulation. A common practice in industry to handle this problem is by diluting purée with water for which flavor reconstitution and sugar addition are required. However such process is not preferred due to the addition of sugar and sensorial drawbacks. The present drawbacks for the current solution incited us to formulate one of the aims of this work which was based on the intimate relation between pectin nanostructure and function. The aim was to utilize different naturally-present pectin modifying enzymes (i.e. pectinases) to tailor the flow properties of mango purée by alteration of pectin nanostructure. To reach the aim, in the first approach, the possibility of using endogenous pectin-degrading enzymes to influence the high consistency of mango purée was investigated. In the second approach, exogenous enzymes (single enzyme and mixtures) with and without an additional application of intensive mechanical disintegration were used. It was shown that the most active endogenous pectin-degrading enzyme, β-galactosidase, being temperature labile but pressure stable, was not able to significantly decrease mango purée consistency. It was observed that the high consistency of mango purée can not be solely related to pectin polymers and their modification. Other polymers such as starch and cellulose also contribute to the high consistency observed whether directly (starch) or indirectly (cellulose). We also observed that the enzymatic treatment significantly changed particle morphology. Our results suggest that particle morphology is an important factor in consistency changes in mango purée. The sequence of the enzymatic and mechanical treatments was found to be crucial to the final consistency observed. In general, the amount of serum is the main parameter having a strong and positive correlation with Bostwick consistency index, meaning that release of water and most likely with some degraded polymers into the serum by the enzymatic treatments decreased the consistency. Although mango processing increases the ease of consumption and mango year round availability, large amounts of mango peel is produced as one of the waste streams of mango processing. It should come as no surprise that currently wasted mango peel has to receive proper attention to sustain mango processing by decreasing downstream concerns. Escaping from the existing environmental limitations imposed by classical pectin extraction using mineral acids, the second aim of this work was to obtain a high quality pectin with a commercial valuable functionality from mango peel. A method of acidic-chelator-assisted pectin extraction isolated, with a higher yield compared to the common extraction technique, a pectin with unique chemical characteristics. The citric acid extracted mango peel pectin was compared with apple pectin in terms of chemical structure and some valuable industrial functional properties to evaluate the functionality as related to pre-determined pectin nanostructure. Despite the high molecular weight of the extracted pectin, a high ratio of neutral sugar branches limited the pectin gelation capacity but contributed to noticeable emulsification properties. The present work showed the potential of a well-known cocktail of exogenous enzymes to tailor mango purée consistency especially when such treatment was combined in a specific sequence with high pressure homogenization. Additionally, a sustainable way of pectin extraction was introduced, by which pectin with valuable functionality was obtained from currently wasted low cost mango peel.status: publishe

The effect of exogenous enzymes and mechanical treatment on mango purée: Microscopic, mesoscopic, and macroscopic evaluation

This paper addresses to what extent mango purée macroscopic properties (consistency) is related to its particle physical properties such as mesoscopic (particle size) and microscopic (morphology) properties. To manipulate mango purée particle sizes, high pressure homogenization (HPH) was used. Commercial fungal and bacterial (cell wall) polysaccharide degrading enzymes without/with HPH (different sequences) were used to understand the contribution of specific (cell wall) polysaccharides and the relevant parameters to consistency changes. The results reflect that, unlike endo-cellulase, pectin methylesterase (PME) together with endo-polygalacturonase (PG), and α-amylase significantly contributed to consistency decrease. HPH only, although largely changing the particle size, did not change the purée consistency, but the combination of HPH with an enzymatic treatment decreased it substantially. Enzymes, while having minimal effect on particle sizes, induced a type-dependent modification of particles’ morphology, showing the accessibility of particle polymers (in addition to the expected serum polymers) to enzymes.High consistency of mango purée that limits its processing is industrially decreased by dilution with water, requiring further flavor reconstitution and sugar addition. The consistency is believed to be related to pectin and starch. As physical and enzymatic pectin modifications are allowed by regulatory authorities, our study aimed at better understanding and controlling the flow properties of mango purée by both physical (high pressure homogenization) and enzymatic polysaccharides manipulations. Our findings highlight that in situ polysaccharide functionalization could be an industrially relevant alternative to commonly used additives in food systems for controlling the sensorial (i.e. taste and texture) properties.status: publishe

The effect of exogenous enzymes and mechanical treatment on mango purée: Effect on the molecular properties of pectic substances

Recent studies showed that the functional properties of food suspensions are determined both by the plant-based particles and the serum properties, and the ratio between these two phases. This paper addresses the effect of enzymatic and high-pressure homogenization (HPH) treatments on the properties of bio-polymers present both in mango purée serum and particle phase. Hereto, fungal and bacterial commercial enzymes such as pectinmethylesterase (PME), endo-polygalacturonase (PG), endo-cellulase (endo-β-glucanase), and α-amylase without/with HPH (20 MPa) were used to treat mango purée. The treated purées were centrifuged in order to independently analyze both the serum and particle phase. The enzymatic treatments resulted in clear structural changes of the bio-polymers present in both phases. The relative amount of the serum phase clearly increased after both “PG and PME” and “α-amylase” treatments although due to different mechanisms. The conformation and weight average molecular weight of the polymers in solution was also significantly affected by both HPH and enzymatic treatments. These findings highlight the effect of enzymatic treatments on both particle and serum phase on fruit and vegetable based suspensions with and without an intense mechanical treatment and clearly show that both phases are accessible and affected leading to a range of opportunities in terms of product design.status: publishe

The effect of high pressure homogenization and endogenous pectin-related enzymes on tomato purée consistency and serum pectin structure

The influence of mechanical tissue disintegration techniques (i.e. blending and high pressure homogenization) and the stimulation of endogenous pectin-related enzymes (i.e. pectin methyl-esterase and polygalacturonase) on tomato purée consistency, serum composition and serum pectin structure were investigated. Serum pectin structure was characterized in terms of degree of methyl-esterification, acetylation, neutral sugar composition and molecular weight (Mw) distribution. Endogenous pectin methyl-esterase and polygalacturonase stimulation resulted in the lowest purée consistency and highest serum yield. However, when such purée was homogenized, a higher purée consistency and a low serum yield were observed. Moreover, the Mw of serum pectin was exceptionally high for the homogenized purées. The low methyl-esterified, linear and remarkably high Mw tomato serum pectin of the homogenized purées partly explains their increased consistency. This work demonstrated that high pressure homogenization can at least partially restore the consistency of tomato purée despite an initial consistency loss ascribed to enzymatic pectin degradation.status: publishe

The use of high pressure homogenization and endogenous enzymes to control tomato purée consistency and serum pectin structure

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Deliberate processing of carrot purées influences purée consistency and serum pectin structures

status: accepte

Functional properties of citric acid extracted mango peel pectin as related to its chemical structure

The objective of this work was to extract and evaluate some functional properties (gelling and emulsification capacity, acidified milk drink stabilization) of pectin extracted from mango peel using an acidic ion chelator (citric acid) (pH 2.5, 2 h at 80 °C). The novel extraction method resulted in a high yield of pectin (MPP – mango peel pectin) having a very high DM (78.1%), high neutral sugar to uronic acid ratio and a high average molecular weight (Mw). Those chemical structural characteristics had a large impact on the obtained functional properties of the pectin. MPP (0.8%) was able to stabilize 5% oil-in-water emulsion for 30 days similarly to pectin from apple that had a comparable DM but a much lower neutral sugar to uronic acid ratio and a much lower Mw. Despite the high Mw that was expected to provide good gelling properties, MPP did not form a strong gel even at high concentrations of pectin and sugar at acidic condition. Such a result is most likely due to high presence of neutral sugar branches sterically hindering the gel network formation resulting in a thickening effect. The large concentration of neutral sugars that might provide interesting health related activities seemed also to limit the utilization of MPP for acidified milk drink stabilization. The unique structural properties of MPP that include a high DM, high Mw and high branching with neutral sugars are responsible for the limitations and further opportunities of functionalization of this polysaccharide obtainable from the by-products of the fruit industry.status: publishe

Thermal and high-pressure stability of pectinmethylesterase, polygalacturonase, β-galactosidase and α-arabinofuranosidase in a tomato matrix: Towards the creation of specific endogenous enzyme populations through processing

The thermal and pressure stability of tomato pectinmethylesterase (PME), polygalacturonase (PG), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af) were investigated in situ. Enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25-95 °C at 0.1 MPa and 10 min at 0.1-800 MPa at 20 °C) was monitored by measuring the residual activity in crude enzyme extracts of treated tomato purée samples. PME was completely inactivated after a 5-min treatment at 75 °C. Only 30 % of the pressure stable PME was inactivated after a treatment at 800 MPa (20 °C, 10 min). A 5-min treatment at 95 °C and a treatment at 550 MPa (20 °C, 10 min) caused complete PG inactivation. β-Gal and α-Af activities were already reduced significantly by thermal treatments at 42.5-52.5 °C and 45-60 °C, respectively. These enzymes were, however, rather pressure resistant: treatments at respectively 700 and 600 MPa were necessary to reduce the activity below 10 % of the initial value. Assuming that first-order, fractional conversion or biphasic inactivation models could be applied to the respective enzyme inactivation data, inactivation rate constants and their temperature or pressure dependence for the different enzymes were determined. Based on differences in process stability of the enzymes, possibilities for the creation of specific "enzyme populations" in tomato purée by selective enzyme inactivation were identified. For industrially relevant process conditions, the enzyme inactivation data obtained for tomato purée were shown to be transferable to intact tomato tissue. © 2012 Springer Science+Business Media New York.status: publishe

Study of mango endogenous pectinases as a tool to engineer mango purée consistency

The objective of this work was to evaluate the possibility of using mango endogenous pectinases to change the viscosity of mango purée. Hereto, the structure of pectic polysaccharide and the presence of sufficiently active endogenous enzymes of ripe mango were determined. Pectin of mango flesh had a high molecular weight and was highly methoxylated. Pectin methylesterase showed a negligible activity which is related to the confirmed presence of a pectin methylesterase inhibitor. Pectin contained relatively high amounts of galactose and considerable β-galactosidase (β-Gal) activity was observed. The possibility of stimulating β-Gal activity during processing (temperature/pressure, time) was investigated. β-Gal of mango was rather temperature labile but pressure stable relatively to the temperature and pressure levels used to inactivate destructive enzymes in industry. Creating processing conditions allowing endogenous β-Gal activity did not substantially change the consistency of mango purée.status: publishe