Science and Technology
Food, Agriculture & Environment Vol.1(2) : 88-92. 2003 www.world-food.net
Application of hydrolyzed carrot pomace as a functional food
ingredient to beverages
Thomas Stoll, Ute Schweiggert, Andreas Schieber* and Reinhold Carle
Institute of Food Technology, Section Plant Foodstuff Technology,
Hohenheim University, Garbenstrasse 25, D-70599 Stuttgart, Germany.*e-mail:firstname.lastname@example.org
Received 12 December 2002, accepted 18 April 2003.
Utilization of a carotene-rich functional food ingredient recovered through mechanical and enzymatic breakdown of the tissue of carrot pomace was
evaluated by its application to model beverages based on cloudy apple juice, aiming at sustainable carrot juice production. Contrary to synthetic ?-carotene
supplements, the stability of the natural ?- and ?-carotene in the beverages proved to be excellent after 20 and 24 weeks storage under moderate and even
intense illumination at 23 and 19°C, respectively. Neither degradation nor isomerization were observed, thus confirming the extraordinary stability of carotenes
in their natural matrix. Furthermore, cloud stabilities as determined by centrifugation and real time sedimentation tests were satisfactory. Although increasing
proportions of pectin only slightly delayed sedimentation of coarse cloud particles, the positive effect of pectin was more pronounced with respect to
improved serum turbidity of the beverages which might be ascribed to higher serum viscosity.
Key words: Beverage technology, carrot pomace, carotene stability, cloud stability, functional food ingredient.
In Europe and in the USA carrots (Daucus carota L. ssp. sativa)
Materials and reagents: Carrot pomace hydrolyzate (3.8 °Bx)
considerably contribute to human ?-carotene intake. Carrot juices
with a total carotene content of 64 mg kg-1, expressed as the sum
and blends thereof are among the most popular non-alcoholic bev-
of ?- and ?-carotene, was recovered from industrially processed
erages. From 1995 to 2000, German carrot juice production in-
carrots cv. ‘Karotan’ (Gemüsesaft GmbH, Neuenstadt/Kocher,
creased by 80 %, actually amounting to 42.2 million liters. De-
Germany) as described previously11. The ?- and ?-carotene ratio
spite considerable improvements in processing techniques includ-
was 0.57. Cloudy apple juice was kindly provided by Streker
ing the use of technical enzymes, mash heating, and decanter tech-
Natursäfte (Aspach, Germany). All reagents and solvents were of
nology, about one third of the raw material remains as pomace
analytical or HPLC grade (Merck, Darmstadt, Germany). All-trans-
which is usually disposed as feed or fertilizer1. Thus, a major part
?-carotene (Type II) and mixed isomers (?- and ?-carotene in a
of valuable compounds such as carotenes, uronic acids and neu-
ratio 1:2) were purchased from Sigma (St. Louis, MO, USA). The
tral sugars is still retained in the pomace2. In recent years, dietary
internal standard ?-apo-8'-carotenal was obtained from Fluka
supplements like ATBC (vitamin supplemented) drinks have at-
(Buchs, Switzerland). Citrus pectin (Type AU 202) with a degree
tained intense consumer attraction. Since the incidence of lung
of esterification of 72.5 % was supplied by Herbstreith & Fox
cancer in smokers was found to be inversely correlated with high
KG (Neuenbürg, Germany).
dosages of synthetic ?-carotene3,4, the former German Federal
Institute for Health Protection of Consumers and Veterinary Medi-
Preparation of model beverages based on cloudy apple juice:
cine (BgVV) recommended smokers to abstain from food and di-
Cloudy apple juice and pomace hydrolyzate were blended to yield
etary supplements fortified with ?-carotene5. According to a more
50 % fruit juice content and 12 mg L-1 total carotene in 45 kg fi-
recent recommendation of the BgVV daily intake of isolated ?-
nal product on pilot plant-scale. Soluble solids, pH, and titratable
carotene should not exceed 2 mg6. In contrast, intake of carotenes
acid as well as fruit juice, ascorbic acid and total carotene content
from fruits and vegetables was recognized as safe and beneficial.
were adjusted according to commercial ATBC and breakfast drinks.
Therefore, carrot pomace is considered a valuable and yet under-
After de-aeration for 10 min in a colloid mill under vacuum
estimated source of natural ?- and ?-carotene present in their
(100 mbar), the product was homogenized at 180 bar and de-aer-
genuine proportions. In the past, only few attempts have been car-
ated again. Weight and soluble solids (°Bx) were determined. Pec-
ried out at utilizing carrot pomace in foods such as bread7, cake,
tin was predissolved in water at approx. 20 °C to obtain a 10 g kg-
dressing and pickles8, and for the production of functional drinks9,
1 solution which was added to the beverage at concentrations of
respectively. However, consumer acceptance of carrot pomace as
0.5 and 1 g kg-1, respectively. Sucrose solution (68 °Bx) was added
a part of the recipe still needs to be demonstrated, especially since
to obtain 12 °Bx in the final product. After addition of ascorbic
sensory quality may be adversely affected. Recently, a novel pro-
acid (0.43 g kg-1) and citric acid (2.3 g kg-1), the blend was adjusted
cess for the complete utilization of carrot pomace as a source of
to the final concentration with water, pasteurized in a tubular heat
carotenes and oligogalacturonic acids has been developed includ-
exchanger (Ruland, Neustadt/Weinstrasse, Germany) at 90°C for
ing mechanical and enzymatic breakdown of the plant matrix10,11.
60 s, hot filled into 0.5 L glass bottles, sealed under superheated
The main objective of this work was to evaluate the potential use
steam (Type SLW 100 Vaporette, Schmalbach-Lubeca, Hannover,
of liquefied carrot pomace as a functional food ingredient. For
Germany), and then water cooled to room temperature. Control
that purpose a carotene-rich hydrolyzate was incorporated in a
samples without addition of pectin and ascorbic acid were also
model beverage based on cloudy apple juice. Particular attention
produced, respectively. The specifications of the model beverage
was paid to carotene and cloud stability during storage.
variants are given in Table 1.
Food, Agriculture & Environment; Vol. 1(2), April 2003
Storage conditions of model beverages: Stability of carotenes
Color measurement: L*a*b* values of the beverages before and
was evaluated after 20 and 24 weeks storage of bottled samples of
at the end of storage under conditions mentioned in Table 2 were
variant 1 and 2 under moderate and intense illumination at 23°C
determined with a Chroma-Meter (Type CR-300, Minolta,
and at room temperature, respectively, as shown in Table 2. Illu-
Langenhagen, Germany). The sample was poured in a Petri dish
mination intensities (lx-values) were measured with a luxmeter
(diameter: 14 cm, height: 2 cm), and L*a*b* values were recorded
(Type Mavolux-digital, Gossen, Nürnberg, Germany).
ten times using standard illuminant D65.
Sample preparation and HPLC analysis of ?- and ?-carotene:
Saponification of the model beverage, which was necessary due
Results and Discussion
to the addition of cloudy apple juice, was carried out according to
Application of the carotene-rich hydrolyzate to model bever-
a modified procedure of Kimura et al.12. An aliquot of 5 mL was
ages: Besides several other possibilities, the most obvious appli-
stirred at room temperature for 30-60 min in 60 mL of petroleum
cation for the carrot pomace hydrolyzate is its utilization as a func-
ether and 30 mL of methanolic KOH (100 g kg-1) under nitrogen.
tional ingredient in non-alcoholic beverages, since ?-carotene
The suspension was filtered through sintered glass (G ) under re-
intake from fruits and vegetables is considered beneficial. In con-
duced pressure, transferred into an amber glass separation funnel,
trast, commercial products, e.g. ATBC and breakfast drinks, pre-
and shaken with 50 mL of sodium chloride solution (100 g kg-1).
dominantly contain synthetic ?-carotene formulations for provi-
After separation, the petroleum ether layer was washed twice with
tamin A supplementation, which has been associated with adverse
water (50 mL). Emulsions were removed by adding a few drops of
effects at high dosages3,4. Moreover, crystalline ?-carotene for-
methanol. The extract was dried with anhydrous sodium sulfate
mulations are usually based on gelatin, whereas for plant food-
(2 g), and petroleum ether was evaporated in vacuo at room tem-
stuffs pectin is a more adequate hydrocolloid15. Consequently,
perature. The resulting residue was dissolved in 2-propanol, 1 mL
model beverages consisting of 50 % apple juice (12 °Bx), 12 mg L-
of a solution of ?-apo-8'-carotenal was added and made up to 5 mL.
1 total carotene, 0 and 0.43 g kg-1 ascorbic acid, 2.3 g kg-1 citric
The determination of carotenes was carried out in duplicate. HPLC
acid, and varying amounts of citrus pectin were prepared. Cloudy
analysis and quantification based on internal standard calibration
apple juice was chosen because of its high cloud stability16. Ana-
with ?-apo-8'-carotenal was performed as described by Marx et
lytical data of a model beverage are exemplified for variant 2 as
al.13 and Stoll et al.11, respectively. Calculated total carotene con-
follows: pH value of 3.2, 5.4 g L-1 titratable acid (calculated as
tents were standardized to soluble solids of 12 °Bx.
citric acid), 12.2 °Bx, sugar-acid-ratio of 22.6, and 4.4 mg L-1 and
7.5 mg L-1 ?- and ?-carotene, respectively.
Characterization of beverages:
Turbidity measurement: The turbidities of the cloudy apple juice
Particle size distribution of model beverages: The particle size
and model beverages before centrifugation (T ) and the turbidi-
distribution of variant 2, expressed as volume percent of the total
ties of their supernatants (sera) after centrifugation (T ; 4200 g,
particles is exemplarily shown in Fig. 1. Approximately 47% of
15 min, 20 °C) were determined. The cloud stability was deduced
particle size ranged from 83-151 µm with a maximum of 17%
from the relative turbidity (T ), according to Reiter et al.14. Tur-
between 101 and 124 µm, 17% occupied category 56-83 µm, and
bidity was determined nephelometrically with a two-beam-pho-
16.8% category 151-224 µm. Furthermore, the volume D[4,3],
tometer (Type LPT 5, Dr. Lange, Düsseldorf, Germany) using
surface D[3,2], length D[2,1], and number D[1,0] mean diameters
50 mm round cuvettes. Samples were diluted with de-ionized wa-
were found to be 117.3, 73.8, 22.9, and 6.2 µm, respectively.
ter. Turbidity was expressed as nephelometric turbidimeter units
(NTU). Additionally, cloud stability was checked during a 170 day
Cloud stability during storage: The amount of coarse particles
sedimentation test. Five bottled samples of variant 2, 3 and 4 were
is a crucial issue for the cloud stability of carrot juices14. A cloud
stored in the dark at about 18°C, respectively. The decrease in
stabilizing potential of pectin on pulp-containing fruit beverages
sediment height, relative to the initial value, was calculated and
was attributed among others to the increasein serum viscosity17.
plotted against storage time.
Therefore, in preliminary laboratory scale experiments, citrus
pectin was added in concentrations from 1 to 10 g kg-1 in 1 g kg-1
increments to evaluate cloud stability as well as mouthfeel. As
described by Mensah-Wilson et al.17, pectin addition neither af-
fected particle size distribution nor volume mean diameter D[4,3].
Particle size distribution: Particle size distributions of the model
Based on these findings beverages containing 0, 0.5, and 1 g kg-1
beverages were determined through laser light scattering with a
pectin were prepared in pilot plant-scale.
Mastersizer E (Malvern Instruments, Herrenberg, Germany) us-
The centrifugation test, primarily developed for cloudy apple
ing a condensing lens with a focal length of 300 mm. Data ob-
juice, is generally useful to predict sedimentation during storage
tained were evaluated using supplier-provided software. Volume
Table 1. Variation of pectin and ascorbic acid content of model
D[4,3], surface D[3,2], length D[2,1], and number D[1,0] mean
beverages produced by addition of carrot pomace hydrolyzate to
diameters were determined for all samples.
cloudy apple juice.
Soluble solids: °Bx-values were determined with a digital
refractometer (Type RX-5000, Atago, Tokyo, Japan).
Pectin (g kg-1)
Titratable acid: The determination of titratable acid in the model
beverages was performed according to IFU method No. 3.
Ascorbic acid (g kg-1)
Food, Agriculture & Environment; Vol. 1(2), April 2003
Table 2. Storage conditions of model beverages for evaluation of carotene stability after 20 and 24 weeks.
Illumination intensity (lx) b
Moderate illumination c
Intense illumination d
a Cf. Table 1
b 24 hrs illumination with artificial light
c Fluorescent lamp: L58W/25 Universal white (Osram, Munich, Germany)
d Four fluorescent lamps: L36W/76 Nature de luxe (Osram)
Turbidity before centrifugation
Turbidity after centrifugation
Cloudy apple juice
Particle size (µm)
0 g kg pectin
0.5 g kg pectin
1 g kg pectin
Figure 1: Particle size distribution of model beverage variant 2
Figure 2: Turbidity and relative turbidity of cloudy apple juice and
model beverages variant 2, 3 and 4 as determined by centrifugation
test (4200 g, 15 min).
Storage time (days)
Figure 3: Sediment height of model beverages variant 2, 3 and 4 as
determined by real time sedimentation test during 170 days of storage.
Storage conditions: dark, about 18°C.
Figure 4: Physical cloud stability of model beverages before (variant
and consequently for evaluation of cloud stability18. The initial
2) and after 170 days (variant 4, 2 and 3) of storage (from left to right).
turbidities of the beverages, the turbidities of the supernatant af-
ter centrifugation (4200 g, 15 min) and their corresponding rela-
trifugation could not be achieved, which was ascribed to a cloud-
tive turbidity values are shown in Fig. 2. As can be seen, the tur-
stable particle fraction with a particle density nearly identical to
bidity of the beverage (variant 4, no pectin added) considerably
the serum density. Surprisingly, despite the enzymatic degrada-
increased after blending cloudy apple juice (630 NTU) with the
tion of the carrot pomace tissue and thus of stabilizing pectic sub-
carrot pomace hydrolyzate, amounting to 2560 NTU. The turbid-
stances, a satisfactory cloud stability of the hydrolyzate in the bev-
ity after centrifugation remained unchanged for both beverages,
erages could be achieved. According to Reiter et al.14, carrot juices
resulting in lower relative turbidities. When adding 0.5 and 1 g kg-
produced by enzymatic mash treatment were characterized by ex-
1 pectin, the turbidities of both beverage and serum slightly in-
treme cloud stability, suggesting that the latter is affected by pro-
creased with a resulting increment of relative turbidity from 9.5
teins rather than by pectic substances.
to 12 and 15.5 %, respectively. Hence the observed increase in
Since previous studies revealed that the rapid centrifugation test
turbidity upon addition of pectin might be attributed to the higher
evidently depended on the type of beverage system17, a real time
serum viscosity. By visual inspection of the sera, fine cloud par-
sedimentation test was additionally carried out during a period of
ticles were shown to be still suspended. As described by Reiter et
170 days. As evidenced in Fig. 3, within the first day after bottling
al.19, complete clarification of carrot juices even after ultra-cen
a rapid sedimentation of coarse cloud particles was observed, re-
Food, Agriculture & Environment; Vol. 1(2), April 2003
sulting in a decline of sediment height, amounting to 13, 12 and
neither affected color nor carotene content during storage. Com-
15 % for variants 2, 3 and 4, respectively. Throughout the remain-
pared to vitamin-supplemented drinks composed of carrot juice
ing storage time the portion of sediment further decreased, reaching
as a natural source of ?-carotene, ATBC drinks containing syn-
80, 79 and 78 % for variants 2, 3 and 4, respectively. Pectin addi-
thetic ?-carotene formulations suffered from higher isomeriza-
tion did not significantly affect clarification behavior of the bev-
tion rates which have been associated with nutritional conse-
erages. The positive effect of pectin, however, became obvious
quences such as reduced provitamin A activity13. For the consumer
since the beverage without pectin was characterized by a more
the problem arises that an exact calculation of the provitamin A
pronounced clarification with a low turbidity value of 83 NTU af-
intake cannot be realized. Whereas in beverages based on syn-
ter 170 days of storage, whereas beverages containing 0.5 and
thetic ?-carotene overages need to be added to compensate losses
1 g kg-1 pectin displayed improved serum turbidities of 153 and
and guarantee the labelled content during the specified shelf life,
241 NTU, respectively. In contrast to the centrifugation tests,
adjustment of ?-carotene content by utilization of hydrolyzed car-
which were carried out for evaluating the prospective long-term
rot pomace appears to be advantageous. So far, legislative or offi-
stabilities of the beverages over one year, supernatant turbidities
cial guidelines concerning acceptable overage levels do not exist.
of the sedimentation tests were much lower, thus demonstrating
The Association of German Chemists recommended that a devia-
the limited applicability of the former assay to predict cloud sta-
tion of ±30 % for provitamin A should be tolerated, however,
bility of this type of beverage systems. On the other hand, Reiter
overages of 50 % of the specified content should not be exceeded22.
et al.19 confirmed that the centrifugation test is also suitable to
separate all fast sedimenting particles with a critical size of
> 10 µm from carrot juices. Nevertheless, by using both tests sat-
isfactory cloud stability and the lack of supernatant clarification
The results obtained in the present study demonstrate that the hy-
was clearly shown. Furthermore, sedimented cloud particles could
drolyzate recovered from carrot pomace may be used as a natural
easily be re-dispersed by slightly shaking the bottle. A visual com-
ingredient of functional soft drinks, as exemplified for cloudy
parison of the model beverages at the beginning and the end of
apple juice. Thus, complete utilization of carrots was achieved by
storage is shown in Fig. 4, impressively pointing out the bright
integration of carrot pomace hydrolysis into the conventional car-
and stable orange color originating from the hydrolyzate. Depend-
rot juice production. Whereas carotene stability of the model bev-
ing on the process stage of acidification during carrot juice pro-
erages based on hydrolyzed carrot pomace was outstanding, cloud
duction, acidifying juices prior to pasteurization always resulted
stability was found to be satisfactory after bottling during long-
in unstable juices, whereas acidification of the coarse mash re-
term storage. Furthermore, extended applications of the carotene-
sulted in highest cloud stability14. Therefore, hydrolysis of carrot
rich hydrolyzate as a coloring food, e.g. in dried products, appear
pomace on acidic conditions resulted in cloud stability when blend-
to be promising. Since water-dispersible synthetic ?-carotene for-
ing with acidic media such as apple juice.
mulations are usually based on gelatin to enhance water solubil-
ity, their application to beverages rich in polyphenolics may re-
Carotene stability: Total carotene content, expressed as the sum
sult in the formation of sensorically unacceptable sediments. In
of ?- and ?-carotene, was determined after 20 weeks of storage
contrast, hydrolyzates obtained from carrot pomace represent a
under moderate illumination (Table 2). No significant degradation
suitable natural alternative for the supplementation of cloudy func-
of the provitamins was observed. Variants 1 and 2 contained 12.4
tional drinks, especially of ATBC-drinks, since ?- and ?-carotene
and 11.7 mg L-1 total carotene at the beginning and 12.0 and
are added in their genuine proportion. Due to the almost com-
12.7 mg L-1 at the end, respectively. Even after six months under
plete degradation of the cell wall polymers, increased
intense illumination total carotene content remained unchanged,
bioavailability of carotenes from carrots may be expected23. More-
resulting in 12.2 and 12.8 mg L-1 for variant 1 and 2, respectively.
over, it has been shown that the hydrolyzate also contains
Moreover, formation of cis-isomers of ?-carotene was not ob-
oligogalacturonic acids (OGAs) as a second functional ingredi-
served even after intense illumination. These findings support the
ent, which was derived from enzymatic hydrolysis of pectic cell
protective role of the natural plant matrix for carotene stability,
wall substances10. OGAs have recently attracted intense interest
as already demonstrated for ATBC-drinks20 and carrot juices13,21.
since they have been demonstrated to inhibit the adherence of bac-
The present study also shows that ?- and ?-carotene are extraor-
teria to epithelial cells and might therefore be used as therapeutic
dinarily stable even after almost complete degradation of the cell
wall polymers (pectin, hemicellulose, cellulose) and confirms that
the physical state of carotenes seems to be the most important
The present work was supported by the Federal Department of
factor in carotene stability. As very recently demonstrated, model
Education and Research (BMBF 0339820). The authors wish to
preparations containing crystalline ?-carotene showed pronounced
thank Mrs S. Bayha and Mr K. Mix for excellent technical assis-
stability during heating, whereas ?-carotene dissolved in toluene
resulted in isomerization21. In addition to the quantification of
carotenes, color of the beverages was monitored by determina-
tion of L*a*b* values. Ascorbic acid was added to variant 2 to
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