“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