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“Color study at storage of lyophilized carrot systems” Alicia del Valle GALLO,1 María del Pilar BUERA,2 Claudio PETRIELLA1 1Departamento

de Tecnología, Universidad Nacional de Luján 2Departamento de Industrias, FCEyN, UBA

AIC 2010 Color and Food, Mar del Plata, Argentina, 12-15 October 2010

Foods derived from fruit and vegetables provide not only water, fiber, vitamins and minerals, but also phytochemicals.

There is evidence that phytochemicals are highly beneficial, because they counteract the oxidative stress induced by free radicals, which is involved in the etiology of a wide range of chronic diseases. Hence, there is a need of antioxidants consumption.

Beneficial effects in prevention of many chronic and degeneratives diseases are attributed to vegetal pigments, mainly through theirs antioxidant properties. β-carotene and lycopene stand out by their antioxidant action. Carrot is the most important source of first, whereas tomato and watermelon are of the second.

The isolated pigments of natural raw material and laboratory synthesized analogs do not present the beneficial properties with equal intensity to that found in vegetal matter studies.

Nevertheless, the fresh raw material is perishable and seasonal and with a variable pigment concentration against the pure pigment preparations.

The encapsulation by freeze-drying is an excellent tool to preserve these compounds.

OBJECTIVE The objective of this work was to study the β-carotene stability in its natural matrix, encapsulated with different molecular weight maltodextrins.

GENERAL OBJETIVES

The study of:

effectiveness

of sugars and related compounds on carotenoid

pigments stabilization

frequent deterioration reactions and their kinetics in relation to storage humidity and physical properties of the medium (glass transition, porosity).

strategies to optimize extraction and carotenoids encapsulation and to improve protective agents effectiveness.

MATERIALS AND METHODS

Pulps preparation

CARROTS

Carrots (Daucus carota) WASHING

PEELING

CUTTING

Peels

Tips and tales

GROUNDING

BLANCHING

ENZYMATIC TREATMENT

Pectolytic Enzymes (hemicelulase and pectinase activities)

Encapsulation and freeze-drying Macerated Pulps Calcium Chloride (MCa), maltose (M) or maltodextrins of different molecular weights (MD40 and MD150)

Rehumidification

Storage

Freeze-drying process

Control samples were made of unblanched (C) or blanched (CE) carrots without enzymatic treatment nor any other substance added.

Freeze-dried samples were equilibrated at three different water activities (aw = 0,11, 0,44 and 0,75) and submitted to accelerated stability tests (55째C) during different time intervals.

The surface color of the samples was measured with a Minolta integrating sphere spectrophotometer and CIELAB L*, a*and b* coordinates obtained.

Electronic microscopy was used to verify the maltodextrins coverage.

RESULTS AND DISCUSSION

RESULTS AND DISCUSSION VEGETABLES CHARACTERIZATION

Parameters

Result

pH

6,8

°Brix

7,8

Acidez total titulable (%ác. cítrico)

1,54

Composition

Yield (%)

Full root

100

Peel

4

Tip and tale

12

Pulps

84

Storage behavior of controls and maltodextrin added samples equilibrated at different water activities

The b*/a* ratio was selected as a good indicator of vegetable color changes in the red-orange hue . As the red pigments decomposes b*/a* noticeably increases. As expected the most remarkable change took place with the unblanched control samples.

LIGHTNESS VARIATION DURING STORAGE

It shows L* values as a function of storage time of several different samples. L* differences during storage are not significant. Nevertheless their initial values were very different according to the composition of the samples.

The initial L* value was affected

both

by

blanching,

enzymatic

treatment

and

matrix

the

structure.

Samples with added calcium have higher L* and also those with less water (low water activity).

The most wet samples have a darker appearance due to a transparency effect caused by water on the structural biopolymers of vegetables (Agudelo-Laverde, 2008).

Luminosity is highly dependent of superficial phenomena, such as porosity, topography, and superficial humidity (Prado et al, 2006).

Figure depicts different freeze-dried carrot samples after 21 days of storage.

At aw = 0.11 can be seen clearly the dilution or coverage effect of color in samples with maltose and maltodextrin. On the other hand the deterioration is greater at high water activities.

aw: 0,75

aw: 0,43

aw: 0,11 CE

Control

MD40

MCa

MD100

MD150

CE

Control

MD40

MCa

MD100

MD150

Scanning electron microscopy of dehydrated carrot systems

Dehydrated carrot systems encapsulated with maltodextrin (Storage final stage )

aw: 0,11

aw: 0,43

aw: 0,75

CONCLUSIONS The lyophilized carrot systems described are more concentrated β-carotene sources than the raw vegetables.

The β-carotene losses during processing and storage could be related to the b*/a* ratio.

Instead, the luminosity values are highly dependent on systems’ composition and on the surface characteristics of samples. While the appearance seems little related to the pigment concentration, it is highly influenced by the water content.

The more unfavorable storage situation corresponds to the greatest water activity studied, 0.75.

In the freeze-dried carrot systems of

intermediate and high water content (aw = 0.43 and 0.75) the encapsulation with MD150 is the one allowing more pigment retention during storage.

The protecting action of maltodextrins was also evidenced by structural studies made with electronic microscopy.

The encapsulation process herein described which combines natural biopolymers and pigments of known antioxidant activity could be a useful tool in the development of innovative functional foods, of adequate appearance and health-promoting properties.

NOVEL PRODUCTS

Formulations: B: carrot+grapefruit+strawberry C: strawberry+carrot D: grapefruit+strawberry

THANKS FOR YOUR ATTENTION