FR2619678A1 - Process for treating endives for their long term preservation in a cool place - Google Patents

Abstract

Process for treating endives comprising the following steps: - trimming, cutting; - washing in an aqueous chlorine solution; - rinsing by spraying; - washing in an aqueous solution comprising an anti-oxidant; - rinsing by soaking; - mechanical draining; - packaging. The aqueous chlorine solution has a concentration of 0.1 mg/l and the treatment time is 1 min. The anti-oxidant is concentrated sodium metabisulphite at 1 g/l and the treatment time is 5 min. Given the density of the endives, the soakings and washes are performed in a bath with bubbling.

Description

Process for the treatment of endives with a view to their long-term fresh preservation.

The present invention relates to a process for the long-term preservation of leaves of raw endives, alone or mixed with other foodstuffs.

Attempts have been made to extend the shelf life of salad leaves without resorting to complex and costly means of preservation. We know that salad is a delicate product very sensitive to temperature, humidity and bacteria, and even more so for the variety called endive.

Lifestyles have also been profoundly changed and eating habits have followed. This is how market demand is moving towards ready-to-use, cut, washed salad bags. It is understood that this requires a prior preparation of the product and its packaging in a special packaging and possibly special storage conditions.

This is how, in the patent application
EP-A1-0201266, it is proposed to treat
Food products in an acid medium, containing a certain amount of sodium metabisulfite and sulfur dioxide, after these same food products have been blanched between 850 and 1000C for about five minutes.

Finally, they are vacuum-packed with partial addition of carbon dioxide.

Such a process is inapplicable to salad leaves, since the blanching would lead to partial cooking and total modifications of the product as it appears in the raw state. As for the acid treatment, it distorts the taste.

Patent application FR-A-2564701 relates to a process for preserving raw and perishable vegetable products, which is broken down into five stages - Washing plants; - Cutting; - Washing with particle-free water
of iron and copper, but added
sodium ascorbate, followed by spinning; - Ultraviolet drying and irradiation; - Vacuum packaging then reinjection
of a gaseous binary compound.

Sodium ascorbate delays the action of oxidants and UV rays destroy surface bacteria. The binary gaseous conservation compound comprises from 20 to 80% of carbon dioxide.

This process is applicable to chicory, fennel, and lettuce in particular. Such a process requires drying which, in essence, does not allow the product to maintain its own humidity level and even less the crispness, when applied to endive.

We also know the certificate of utility FR-B-2340687 which is applicable to leafy vegetables. The process proposes cutting the leaves, carrying out a washing in an aqueous solution of chlorine and a wringing, and conditioning the product thus wrung in a bag after having partially removed the air therefrom.

The chlorine concentrations vary from 70 to 150 ppm and the temperature is preferably between 10 and 15.50C, the immersion time being between 5 and 20 seconds.

The latter process has the major drawback of allowing chlorine particles to remain, even after spinning, which adversely affects the quality of the final product; moreover, this process, applied to endive, poses significant coloring problems due to oxidation.

The present invention overcomes these drawbacks and proposes a process for preparing endive leaves with a view to their conservation, which is characterized by the succession of the following stages: - trimming, cutting; - washing in an aqueous chlorine solution; - spray rinsing; - washing with an aqueous solution comprising
an anti-oxygen agent; - rinsing by soaking; - mechanical spin; - conditioning ; - cool storage.

The anti-oxygen agent is sodium metabisulfite.

All the process steps take place with liquids at 20C and an ambient temperature at 50C except the trimming which takes place between 10 and 120C.

This process makes it possible to obtain endives whose conservation is carried out at 2 or 30C without there being any deterioration of the product, both in terms of organoleptic and sensory properties.

Such a process allows easy and long-term conservation of a very sensitive product.

The present invention will be better understood on reading the description of a processing mode according to the invention.

The raw material must meet a certain number of criteria in order to be able to achieve the proposed goal, namely a clean salad, trimmed and cut, therefore ready to use, without additives or preservatives, alone or in combination with other types salad.

The endives are stored at a temperature of 2 to 30C, classic for this type of vegetable.

A humidity of 95% must be respected in order to avoid any wilting. Finally storage must generally be limited to two or three days, out of season, up to seven days, in full season, taking into account the quality of the raw material. The endives are then trimmed, that is to say that the parts which are not perfectly healthy are eliminated: leaves stained for example, likewise the endives are leafless and the core is removed. This removes a significant source of contamination and oxidation. This operation must be carried out at a temperature which limits oxidation, but this operation being manual, 100C seems to be a good compromise. The cut must be rapid, always to avoid browning by oxidation, and, in this case, the working temperature can be lowered to 50C, when this operation is automatic.The product is cut, not including the core, according to variable widths . For example, The first cut is made 55-60 mm from the top, along the longitudinal axis, the second cut has a width of 21 mm.

Thus the widths are diversified, while respecting a minimum width of 10 mm, and the losses are optimized. Only the core is lost.

These cut sheets are then washed with chlorinated water and, in order to obtain maximum efficiency, this washing is carried out by soaking. The material having a density of less than 1, it is necessary to carry out this soaking in a bath equipped with a bubbling system. The chlorinated water in the bath is renewed in portions in order to keep the same chlorine concentration in the bath. On the other hand, the aqueous solution is brought to a temperature of 20C, which is the soaking temperature, while the ambient temperature is around 50C. The chlorine concentration retained is 0.1 mg / l and the time is 1 min. This time does not require great precision, because the chlorine acts only on the surface, and the rinsing which follows will have to be adjusted to the soaking time and the quantity of product. The time of one minute is satisfactory, which is confirmed by the bacteriological analysis which will be studied in more detail later.

The proposed rinsing is done by spraying and its purpose is to eliminate bad flavors from the finished product. The rinse water must be at 20C and the duration chosen, which corresponds to soaking for 1 min in chlorinated water, is 1.5 min.

The rinsed leaves are then washed in an aqueous solution comprising an anti-oxygen agent. This agent can advantageously be E 223 or any sodium metabisulfite "for food use", that is to say corresponding to a certain criterion of purity of SO 2 and to a minimum percentage of impurities such as Iron or Selenium according to the current standards. The chosen concentration is 1 g / l and the soaking time is fixed at this concentration at 5 min. In this case, it is necessary to perfectly respect the concentration-time couple, because bad flavors of the finished product could appear.

The bath is at 2 "C., with bubbling, and the ambient temperature at 50 C. The advantage of this stage lies in the fact that the browning phenomenon is delayed by reduction of the oxidation. The color does not degrade and the sensory analysis is improved.

This step must be followed by an effective rinsing by soaking with bubbling in water at 2 "C and an environment at 50C.

The duration is 1.5 months.

The various soaks and other washes must be, even if they do not require great precision except for the antioxidant treatment, of a limited duration so that there is not too much water retention in the leaf itself, which would have detrimental consequences for conservation.

Spinning is classic; more generally, a centrifuge or other mechanical means is used and the duration, depending on the working conditions, must lead to a residual moisture on the plant of 2 to 3% more.

This operation is also! performed in an atmosphere at 50C.

Finally, the packaging in sachets also operates at 50C. Depending on the size of the sachet and the needs of the distribution, the internal pressure can be adapted so that the sachet is sufficiently inflated and that the consumer, when he chooses, does not degrade the content too much.

The bag must allow endive breathing to be controlled and prevent greening in the light. A suitable material is polypropylene 35 microns thick sold commercially under the reference M8400, OPP from the company MOBIL.

Packaging in sachets is followed by packaging in cartons; material that allows satisfactory plant respiration.

The finished product is stored at 2-30C and the humidity must be maintained at 85 X in order to avoid condensation phenomena in the sachet.

The analysis of the endive leaves thus conditioned makes it possible to define the characteristics of this product: - Absence of a particular odor other than
that of the fresh product after twelve days
conservation; - Absence of color degradation after
twelve days of storage; - Flavor very close to the fresh product after
twelve days of storage; - Crunchy without significant loss compared
to fresh produce after twelve days of
conservation.

- Value of FTAM (total aerobic flora
mesophilic), expressed by the logarithm
the number of germs per gram, inclusive
between 4.6 and 5.9 after seven days of storage
for a degree of quality called "satisfactory".

- Less than 10 fecal coliforms up to
sell-by date ; - Absence of salmonella until the date
of expiration.

It is understood that the example of treatment which has just been given is not limiting and may include variants which would be within the reach of those skilled in the art.

Thus, the bubble bath can be replaced by immersing the leaves using a closed basket.

Furthermore, such a process applicable to the chicory species for the "endive" variety as described above is fully transposable to the varieties: TREVISE; VERONA RED; CHIOGGIA.

Claims (11)

Claims 1. A method of treating endive leaves for long-term preservation, alone or in combination with other food products, characterized in that the leaves undergo the following treatment steps: a) trimming, cutting; b) Washing in an aqueous chlorine solution; c) Rinsing by spraying d) Washing with an aqueous solution comprising  an anti-oxygen agent; e) soaking rinse; f) Mechanical spinning; g) Packaging under partial vacuum; h) Cool storage. 2. Method according to claim 1, characterized in that step a) is carried out at a temperature between 10 and 120C and includes stripping and removal of the core. 3. Method according to claim 1, characterized in that the aqueous solution of step b) is dosed with 0.1 mg of chlorine per liter and in that the soaking time is one minute. 4. Method according to claim 1, characterized in that the anti-oxygen agent is sodium metabisulfite. 5. Method according to claim 4, characterized in that the sodium metabisulfite is dosed at 1 g / l and in that the soaking time is five minutes. 6. Method according to claim 1, characterized in that the soaking time of step e) is 1.5 min. 7. Method according to claim 1, characterized in that the spin is obtained by centrifugation. 8. Method according to claim 1, characterized in that the packaging is a polypropylene film sachet 35 microns thick, allowing respiration of the plant, filled and sealed under partial vacuum. 9. Method according to any one of claims 1, 3, 4, 5, and 6, characterized in that the washing and rinsing by soaking are carried out in a bath with bubbling. 10. Method according to claim 1, characterized in that steps b) to h) are carried out with liquids at a temperature of 20C and an ambient temperature of 50C. 11. Method according to any one of the preceding claims, characterized in that the endive leaves are cut along the axis of the plant, from the top, 60 mm for the first, 21 mm for the middle and the rest in 10 mm increments.