WO2019102076A1

WO2019102076A1 - Hydrolysis of vanilla aroma precursors at negative temperature

Info

Publication number: WO2019102076A1
Application number: PCT/FR2018/000237
Authority: WO
Inventors: Eric ODOUX
Original assignee: Odoux Eric
Priority date: 2017-11-21
Filing date: 2018-10-20
Publication date: 2019-05-31
Also published as: FR3073714A1; FR3073714B1

Abstract

A method for processing green vanilla through the action of endogenous fruit enzymes at negative temperatures. The methods currently used for processing green vanilla, and based on the action of one or more endogenous fruit enzymes, are carried out under temperature conditions which promote hydrolysis of glycosyl precursors of the fruit, and in particular glucovanillin. These conditions also promote reactions leading to the loss of vanillin and certain other aglycones, which is undesired. The invention described in the present patent, enables hydrolysis of these glycosyl precursors to be carried out at slightly negative temperatures, which temperatures also prevent reactions leading to the loss of free aglycones and, more particularly, vanillin. This simple to implement method is intended, in particular, for processing green vanilla, whatever the species concerned.

Description

Negative Temperature Hydrolysis of Vanilla Aroma Precursors

Technical Field of the Invention

The present invention describes a. process of transformation of green vanilla (vanilla fruit, family Orchidaceae, genus Vanilla), based solely on the action of the endogenous enzyme (s) of the fruit - without any addition of exogenous enzymes or other products, natural or not - and allowing hydrolysis of substantially complete glucovanillin (and other glycosides) substantially avoiding any loss of vanillin (and their respective aglycones).

Problem and state of the art:

The genus Vanilla has over a hundred species, the most widely cultivated commercially is Vanilla planifolia G. Jackson [syn. V. Andrews fragrans, V. fragrans (Salisbury) Ames, etc ...]. Other species, such as V.

JW Moore tahitensis, V. pompona or V. odorata, are also grown for commercial purposes but on a smaller scale. Vanilla species differ, among other things, in the composition of glycosylated precursors of their green fruits. These glycosylated precursors can be hydrolysed by one or more endogenous enzymes having a glucosidic activity, and lead to the release of their respective aglycones, which aglycones have or not organoleptic properties of industrial interest. This hydrolysis occurs naturally during the maturation of the fruit, but at a very advanced stage - during senescence - and also during the transformation processes developed by men over the ages, which differ according to the production zones. and according to the species cultivated. The aglycones thus released are more or less reactive according to their chemical class and can themselves become secondary reaction substrates leading to more or less chemical modifications. of the original aglycone and to a greater or lesser extent

important.

The most studied case study concerns the reactivity of vanillin, the aglycone released after the hydrolysis of its precursor, glucovanillin, given the economic importance of this molecule, particularly in the fruit of the most cultivated species, Vanilla planifolia G. Jackson. This reactivity would lead to a polymerization of vanillin (on the model of enzymatic or non-enzymatic browning reactions, like Maillard reactions), which results in significant vanillin losses relative to the initial potential of the green fruit. Whatever the exact nature of this phenomenon, from a technological and industrial point of view, the management of these antagonistic reactions that are the hydrolysis of glucovanillin and vanillin losses is a complicated problem because:

1- they occur simultaneously, with only a difference of their initiation in time, since the product of the 1 ^st reaction, vanillin, becomes, as and when it is produced, and as soon as it is in sufficient concentration, the substrate of the 2 ^nd reaction.

2- conditions that are classically favorable for the hydrolysis of glucovanillin

(including sufficient temperature and water activity) are also favorable conditions for vanillin losses.

3 - Conditions unfavorable to vanillin losses (temperature and / or activity of water sufficiently low) are also conditions that are classically unfavorable to the hydrolysis of glucovanillin, and can therefore only be applied if the hydrolysis is almost complete. that is, at a stage where vanillin losses are already significant.

Answering this problem can be summed up fundamentally in identifying conditions favorable to the hydrolysis of glucovanillin and unfavorable to vanillin losses, that is to say, to dissociate these 2 antagonistic reactions over time; the ideal solution is to identify conditions which make it possible to completely prevent vanillin losses, but which nevertheless allow the hydrolysis of glucovanillin to proceed. In practice, the traditional process of processing vanilla most widely used in production areas (Madagascar in particular), and which can be considered as the reference, inevitably leads to vanillin losses greater than 50% of the initial potential.

The patented industrial solutions based on the action of the endogenous enzyme of the fruit (USPO 2274120, USP 2621 127, USPO 2835591, USPO 3352690, USP 3663238, EP 0354118B1, US 201 1 / 0081448A1) do not make it possible to respond to the exposed problem because they are mainly based on optimization of the kinetics of hydrolysis of glucovanillin (contact between enzyme and substrate, temperature, etc ...), which does not have a sufficient impact on the losses in vanillin because the 2 antagonistic reactions are not sufficiently dissociated.

Industrial solutions based on the addition of commercial enzyme (WO

9304597A, WO2004 / 091316A1, WO 2010 / 066060A1, US Pat. No. 7803412B1) make it possible to significantly accelerate the kinetics of hydrolysis of glucovanillin, and can thus considerably limit vanillin losses, even if the vanillin loss reactions are not not formally stopped. However, they affect the overall aromatic profile and have different

disadvantages (higher production costs, implementation on more complex production sites, appellation of vanilla extracts obtained, etc.).

Presentation of the invention

The process described according to this patent makes it possible to respond to the problem by avoiding the various disadvantages inherent in patented processes.

previously. Indeed, the basic principle of the invention is to carry out the hydrolysis of glucovanillin (and other glycosides) in situ by the endogenous enzyme (s) of the fruit at temperatures below 0 ° C., without any other addition of Exogenous products, natural or not. This possibility of performing an enzymatic hydrolysis of the glycosylated precursors under these temperature conditions in the vanilla fruit is totally counter-intuitive for those skilled in the art and can not lead to sufficiently sufficient levels of hydrolysis of glucovanillin. high, only with fruits that have reached a particular stage of maturity, for reasons that are not known. In these conditions of At temperatures, the vanillin released remains chemically stable and does not become a secondary reaction substrate, which allows its initial potential to remain intact or virtually intact; this phenomenon also concerns certain other chemically reactive aglycones.

The detailed description of the process which is the subject of this patent is as follows:

Vanilla ripening stage: Vanilla must be harvested at an optimum maturity stage and / or subjected to a post-harvest maturation stage, for example on the model of what can be achieved with certain climacteric fruits. As this maturation progresses, the fruits that are considered mature are taken to undergo the heat treatment step described in paragraph 2. One skilled in the art will be able to distinguish the fruit not mature ripe fruit based on visual criteria known to professionals in the field and its experience of vanilla. This stage of sorting the vanilla is essential because the stage of maturity is closely correlated with the rates

hydrolysis of glucovanillin (and other glycosides) obtained in the next step. 2- Heat treatment step: The pods selected in the preceding step are placed at a temperature below 0 ° C but not below -15 ° C, the optimum temperature being between -1 ° C and -8 ° C. The vanilla pods are maintained at these temperatures for a period of between 2 days and 50 days, the optimal duration being between 5 days and 20 days. Subject to these temperature conditions, the vanilla browns gradually and changes from its green color at the usual harvest stage to a very dark brown color, even black. This heat treatment step can be carried out on whole pods, cut into pieces or crushed according to the subsequent stages of stabilization and storage that will be envisaged (extraction, drying, etc.). Embodiment of the invention

1.856 g of green vanilla from Reunion Island are matured post-harvest on receipt in a carton at room temperature; between the day of reception and the end of the maturation stage, in this case 8 days, sorting is performed daily to select the vanilla considered as being able to undergo the rest of the process.

The selected vanilla is cut into 1 cm long pieces and 15% by weight of this vanilla are taken at random and frozen at -18 ° C to form a representative sample to determine the value of the initial vanillin potential and serve as a sample. witness. The remaining 85% is placed in a glass jar and the jar is placed in a freezer whose thermostat is set to reach a vanilla temperature of -2 ° C (the original thermostat has been replaced by a thermostat universal adjustable over a temperature control range between + 30 ° C and -30 ° C).

This operation is repeated daily during the 8 days of maturation, until all the vanilla pods have matured. At the end of this protocol, 278 g of green vanilla was thus frozen at -18 ° C, constituting the control, and 1.578 g of green vanilla were placed at -2 ° C, constituting the test.

After 15 days of treatment at -2 ° C, the pot ¹ is released and vanilla become completely dark brown, is placed at -18 ° C until the complete batch is processed. This operation is repeated daily, and so each pot that has reached 15 days of treatment is taken out and the vanilla is stored at -18 ° C. When the last pot is out, the 1,578 g of vanilla are mixed and homogenized, and representative sampling, about 15% of the initial total mass, ie 278 g also (about 18% of the mass of the test), is taken to determine the levels of glucovanillin and vanillin in the test.

The control shows a vanillin potential content of 3.3 g / 100 g of dry matter (DM), of which 3.1 g / 100 g MS in the glucovanillin form and 0.2 g / 100 g DM in vanillin form (a about 6% hydrolysis), while the test shows a vanillin potential content of 3.2 g / 100 g MS of which 0.3 g / 100 MS as glucovanillin and 2.9 g / 100 g MS in the form of vanillin; which means that the vanillin losses can be evaluated at 0.1 g / 100 g MS (below the margin of error related to sampling, extraction and analysis) and the rate of hydrolysis of the approximately 91% glucovanillin (whether or not a possible vanillin loss is taken into account).

Thus, by treatment of the vanilla according to the invention described, hydrolysis of the glucovanillin is almost complete and vanillin losses substantially zero, at least insignificant.

Summary diagram of the test and sampling protocol

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HPLC Analyzes Industrial application:

Given its simplicity, both in terms of implementation and technology used, the industrial application of the present invention is particularly intended for the processing of green vanilla, regardless of the species concerned.

Applications may nonetheless potentially be extended to any product whose endogenous enzymatic activity releases a molecule of unstable interest from a precursor, such as for example certain molecules constituting the aroma of tea during its transformation.

Claims

1) Process for transforming green vanilla characterized in that the green vanilla pods - whole, cut into pieces or crushed - are subjected after harvest to a heat treatment at a temperature between 0 and - 15 ° C for a period of time between 2 and 50 days.

2) Process according to claim 1, characterized in that the heat treatment is carried out at a temperature between -1 and -8 ° C.

3) Process according to claim 1 or 2, characterized in that the heat treatment is carried out for a period of between 5 and 20 days. 4) Method according to one of claims 1 to 3, characterized in that the green vanilla pods were harvested on the plant at an optimum stage of maturity.

5) Method according to one of claims 1 to 3, characterized in that the green vanilla pods have undergone a post-harvest treatment adapted ripening.