Download full-text PDF

Carbohydrate Changes in Parsnip (Pastinaca sativa L.) during Long-Term Cold Storage

Conference Paper (PDF Available) inActa horticulturae 1079(1079) · June 2014with199 Reads
DOI: 10.17660/ActaHortic.2015.1079.91
Conference: Conference: V International Conference Postharvest Unlimited, At Cyprus, Volume: Acta Horticulturae, 1079
Abstract
The purpose of this study was to examine the effect of harvest time (November or January) and postharvest treatments (hot water, H2O2, NaOCl and non-washed – control) of parsnip roots (Pastinaca sativa ‘Banatski dugi’ – old domestic cultivar) and effects on the quantitative and qualitative changes during different storage conditions (S-1 0±1°C; >95% RH or S-2 0-5°C; 85-92% RH). Water loss and quality changes in parsnip taproot were monitored after 60, 120 and 180 days of storage. At the end of storage the percentage water loss ranged from 4.71% (from second harvest inside the S-1 unwashed-control roots) to 26.0% (second harvest in S-2 with H2O2 treatment). Dry matter (DM) values varied from year and harvest time (21.36-23.83%). The DM content of parsnip roots increased gradually during cold storage up to 33.3% (in S-2 with hot water treatment). This increase in DM was followed by a significant (P0.05) increase towards the end of cold storage, indicating water loss. Total sugar content is highly dependent on year and harvest time (9.57-10.69%). During storage, sugar content increased more in S-2 cooling room. Reducing sugar to non-reducing sugar (R/NR) ratio was around 1:10 and showed an increasing trend during storage. Sucrose is the predominant sugar in parsnip roots (8.51-10.05%). Content of glucose (0.35-0.40%) and fructose (0.10- 0.33%) is much smaller. Depending on storage condition and postharvest treatment, glucose and fructose concentrations also increased significantly during cold storage, but to a much lower level than sucrose. Starch concentrations (4.50-5.43% at harvest time) during first month in cold storage declined to <10% of their initial level. The total conversion of starch into sucrose occurs after the second month of storage and starch level almost completely depleted (0.04%). Accumulation of sucrose may raise the culinary quality of cold-stored parsnip.
Figures
667
Carbohydrate Changes in Parsnip (Pastinaca sativa L.) during Long-
Term Cold Storage
Z.S. Ilić and L. Šunić
Faculty of Agriculture Priština-Lešak
Kopaonička bb, 38219 Lešak
Serbia
Keywords: parsnip, harvest time, postharvest treatment, storage condition, quality
Abstract
The purpose of this study was to examine the effect of harvest time
(November or January) and postharvest treatments (hot water, H2O2, NaOCl and
non-washed – control) of parsnip roots (Pastinaca sativa ‘Banatski dugi’ – old
domestic cultivar) and effects on the quantitative and qualitative changes during
different storage conditions (S-1 0±1°C; >95% RH or S-2 0-5°C; 85-92% RH).
Water loss and quality changes in parsnip taproot were monitored after 60, 120 and
180 days of storage. At the end of storage the percentage water loss ranged from
4.71% (from second harvest inside the S-1 unwashed-control roots) to 26.0%
(second harvest in S-2 with H2O2 treatment). Dry matter (DM) values varied from
year and harvest time (21.36-23.83%). The DM content of parsnip roots increased
gradually during cold storage up to 33.3% (in S-2 with hot water treatment). This
increase in DM was followed by a significant (P0.05) increase towards the end of
cold storage, indicating water loss. Total sugar content is highly dependent on year
and harvest time (9.57-10.69%). During storage, sugar content increased more in S-2
cooling room. Reducing sugar to non-reducing sugar (R/NR) ratio was around 1:10
and showed an increasing trend during storage. Sucrose is the predominant sugar in
parsnip roots (8.51-10.05%). Content of glucose (0.35-0.40%) and fructose (0.10-
0.33%) is much smaller. Depending on storage condition and postharvest treatment,
glucose and fructose concentrations also increased significantly during cold storage,
but to a much lower level than sucrose. Starch concentrations (4.50-5.43% at harvest
time) during first month in cold storage declined to <10% of their initial level. The
total conversion of starch into sucrose occurs after the second month of storage and
starch level almost completely depleted (0.04%). Accumulation of sucrose may raise
the culinary quality of cold-stored parsnip.
INTRODUCTION
Parsnip is a vegetable with high nutritional value and dietetic quality. The storage
roots of parsnip contain considerable amounts of sugar, protein and vitamins C, B1, B2
and B6. The value of parsnip is also enhanced due to the content of fibre such as pectin,
and minerals that include potassium, phosphorus, calcium, and iron. Parsnip is a
promising source of dietary fibres with relatively high values of the dry matter. In the
parsnip production areas of Serbia (South Banat region), the most common storage
method which farmers employ is to leave the mature product unharvested in the field
during the winter period and harvest only when the product is about to be sold. The
advantage of keeping them in the soil (as they tend to shrivel and lose weight quite easily)
over winter is an improvement in taste (root tastes sweeter) which occurs when exposed
to frost as it converts starch into sugar. These storage methods can result in crop losses
estimated to be as high as 25-30%, with damage mostly occurring when there is soil
freezing (Ilić et al., 2013). Parsnips are harvested in the late fall, preferable after frost.
The delicate structure of the parsnip root makes it particularly sensitive to mechanical
damage which can occur during soil freezing. An important component of parsnip quality
is sweetness, which is enhanced by exposure to frost. The roots can then be stored 2 to
6 months in 0°C with 95-100% RH (Toivonen, 2004; Israelsson, 2000).
The two basic conditions, as recommended by previous researchers are
Proc. Vth International Conference Postharvest Unlimited
Eds.: G.A. Manganaris et al.
Acta Hort. 1079, ISHS 2015
668
temperature of 0°C and the relative humidity of 98%. The typical postharvest procedure
of root vegetables handling involves product washing, topping, chemical treatment, and
packaging prior to storage or immediate marketing. Chlorination of process water is one
of the primary elements of a proper postharvest sanitation program. Calcium chloride,
hydrogen peroxide and hot water treatment was very effective in controlling decay.
Another storage method involves placing harvested root on wooden boxes (Kora et al.,
2005) with soil into different types of storage room. The most significant changes in
postharvest quality are wilting, weight loss, bacterial deterioration, discoloration, rooting
and sprouting. Soluble solids and sugars content showed a tendency to increase during the
storage period. All of these changes can be prevented by different methods including cold
storage, and postharvest treatment.
The aim of this study was to determine the effectiveness of pre-storage treatment
in maintaining the quality of parsnip during prolonged cold storage.
MATERIALS AND METHODS
Plant Material
The parsnip (Pastinaca sativa L.) cultivar ‘Banatski dugi’ is an old domestic
cultivar for open field production during fall, autumn and winter. For this study, soil
conditions were well drained and sandy, and drip irrigation was used. Parsley was
cultivated in accordance to commonly accepted recommendations (land preparation,
sowing date, plant density, nutrition, plant protection of the crop). Seeds were sown at the
beginning of July (second sowing, after peas) and roots were harvested in the middle of
November as first harvest date (around 110 days after sowing) or 5 January at second
harvest. Uniformly sized taproots at their full maturity stage, with weight of about 250 g,
were picked directly from a field in the south part of Banat (village Debeljača). Medium
sized parsnips are the best quality, preferably around 50-70 mm shoulder diameter and
approximately 190-250 mm in length. Avoid large coarse roots which usually have
woody or fibrous centres. Traditionally, harvesting starts after the first frost (end of
October) and went on until April (depending on the demand). Firm taproots without
defects or diseases, of same size, shape and injury free were selected for the experiment.
The parsnip went into storage on 10 November or 5 January, and the study was
terminated on 10 May.
Postharvest Treatments
The following postharvest washing treatments were conducted: 1) hot water
washing and brushing (50°C for 1 min); 2) 1% H2O2 (tap water for 1 min); 3) 175 ppm
NaOCl (tap water for 1 min); and 4) control, non-washed roots (with soil).
Storage Conditions
Following treatment, the taproots were stored for 160 days at different storage
conditions. The taproots were stored at 0°C, in a cold room (S-1) with high relative
humidity (RH 95-98%) in the dark, or (S-2) in a cooling room with a temperature of 0-
2°C and uncontrolled conditions of relative humidity (RH 85-92%). For each postharvest
treatment, 25 roots per replicate were sampled for analysis, with 4 replicates analysed in
total. After 160 days storage at either temperature, the taproots were transferred to 20°C
for 20 days to simulate marketing practices. Analysis of dry matter, TSS, total sugar,
reducing sugar and vitamin C was completed after 60, 120 and 180 days of storage.
Reducing Sugar Analysis
The reducing sugar of carrots was determined using the Fehling method. This
method can be used as a basis for the analysis of reducing sugars. Fehling’s solution
contains Cu2+ ions that can be reduced by some sugars to Cu+ ions. As the Fehling’s
solution is added the blue Cu2+ ions will be reduced to Cu+ ions. These will precipitate out
of solution as red Cu+ ions. The resulting solution will be colourless. A titration can be
669
carried out to determine an equivalent amount of the sugar to the Fehling’s solution. The
end point would be when the blue colour has just disappeared. This reaction can be used
for the quantitative analysis of reducing sugars.
Sugars are extracted using ethanol, then starch is hydrolysed using hydrochloric
acid and the resultant glucose is extracted after neutralisation. Sugars are determined in
the extracts after oxidation using copper reagent, linked to the reduction of potassium
iodide to iodine, and titration of iodine with sodium thiosulphate.
Staining of Starch in Root Tissues
Pieces of the cross-sections of root (ca. 2 mm-thick) were immersed in Lugol
solution (Merck AG) and incubated on a rotary shaker at room temperature for 10 min.
The pieces were then transferred into a beaker and washed three-times in tap water for
15 min each.The wet pieces were placed on the glass plate of a digital scanner for
scanning.
Data Analysis
All data were subjected to one- or two-way statistical analysis at P=0.05 using
JMP6 Statistical Analysis Software Program (SAS Institute Inc. Cary, NC, USA).
RESULTS AND DISCUSSION
The principal factors which can be used to estimate the length of postharvest life
of parsnip include the time of harvest, stage of maturity at harvest, postharvest handling
and storage conditions. Storage conditions are among the main factors influencing
changes of root vegetables quality during postharvest period.
The moisture content of the refrigerated parsnips decreased with time of storage.
The relative humidity measured inside the S-1 sophisticated cooling room conditions
ranged from 95 to 98%, whereas the relative humidity under simple refrigerated storage
varied from 85 to 92%. The low relative humidity under the refrigerated storage may have
contributed to the decrease in moisture content of the parsnips with time.
Water losses (shrivelling) was the most important cause of postharvest losses of
parsnip and depending on the stage of maturity (harvest date) storage condition and
prestorage treatment. At the end of 180 days of storage period the percentage mass losses
ranged from 6.55% (inside the S-1 cooling room in unwashed-control roots) to 25.24%
(inside the S-2 storage room with H2O2 treatment) (Table 1).
A same trend was observed also at second harvest where the lowest water losses in
S-1 storage (4.71%) were recorded in treatment with NaOCl, but more significantly the
highest water losses were observed in S-2 storage with H2O2 (26.0%) and hot water
treatment (25.21%) (Table 2).
The rate of water loss of root vegetables is affected by the surface area of the root,
the water vapour pressure deficit and air velocity (Correa et al., 2012). Water loss due to
transpiration results in shrivelling, loss of bright colour and increased risk of postharvest
decay. A 7% weight loss is reported to make parsnips unsalable. Because parsnips are
susceptible to wilting, humidity must be kept high. Maintaining sufficiently high humidity
may be a problem, particularly in cold storage. Ventilated plastic crate liners help to
prevent moisture loss. Surface browning in parsnips is a significant problem during
prolonged storage period. Postharvest dips have been demonstrated to reduce browning in
whole parsnips during storage. Dip solutions can contain compounds known to reduce
tissue browning like ascorbic acid, citric acid or calcium chloride (Toivonen, 1992).
Parsnips contain sugars which impart a sweet taste to the vegetable. The
carbohydrate in parsnips is stored in the form of sugars. This contrasts with the potato
where the carbohydrate is 90% starch. In this research, we observed that the dry matter-
DM values varied from year and harvest time (21.36-23.83%). Parsnip from both harvest
time during SP in S-2 cooling room increased DM (up to 33.30% in hot water treatment)
except root from first harvest at second year in S-1 (DM stay on same level). This allows
the starches to convert into sugar, giving the parsnip its unique, sweet nutty flavour. Good
670
market quality is the result of starch changing to sugar which occurs after 2 to 3 weeks in
cold storage.
Total soluble sugars were calculated as the sum of fructose, glucose and sucrose
(Sujojala, 2000). Parsnips are considered sweeter than carrots with almost three quarters
of the sugar in parsnips as sucrose. By comparison, sucrose accounts for only one third of
the sugar in carrots. Total sugar content depends on year and harvest time (9.57-10.69%).
During storage the sugar content increased more in S-2 cooling room (Fig. 1).
Non-reducing sugar content takes around 90% of total sugar content. Same trend
manifested during storage period with non-reducing sugar as total sugar content. Also,
non-reducing sugar increased more in S-2 cooling room that in S-1 cooling room.
Reducing sugar in parsnips of around 1.2±0.30% was observed in 0 days and this content
stays at same level during the whole storage period (Fig. 2).
Sucrose is the predominant sugar in parsnip roots (Rutherford, 1977). Content of
sucrose was 8.37-9.93% and increased during storage, with some difference between
storage conditions and postharvest treatments. The content of glucose (0.35-0.40%) and
fructose (0.10-0.33%) did not change significantly during storage (Fig. 3).
Sucrose to hexose (glucose+fructose) ratio (S/H ratio) was between 1:10 to 1:19
and increased slowly during storage. The increase in sucrose induced by low temperature
in starch-containing plant organs is a widespread phenomenon and has also been observed
in other members of the Apiaceae. Sugar accumulation was more rapid in roots stored at
0°C than at 10°C and in the core than in the cortex. Roots stored at 0°C were perceived to
be sweeter than roots stored for the same period at 10°C or freshly-harvested roots,
suggesting that an improvement in the eating quality of parsnip roots during short-term
cold storage is possible, but would be temperature dependent (Shattuck et al., 1989).
The storage polysaccharide in parsnip is starch. The dietary fibre in parsnip mainly
comprises the cell wall polysaccharides (cellulose, hemicellulose, and pectin substances).
Parsnip roots from the second harvest, most of the hydrolysis of starch into sugars has
already occurred in the field and additional low temperature conditioning during storage
results in complete hydrolysis of starch. The total conversion of starch into sucrose occurs
during the second month of storage (4.50% at harvest time to 0.04% after 60 days).
Staining cross-sections of root with Lugol solution after 8 weeks cold storage,
demonstrated that the starch had completely disappeared from the stele during cold
storage, with weak staining evident in the cortex (Fig. 4).
Low-temperature storage (2°C) decreased the starch content dramatically and
concomitantly increased the sucrose content (Bufler, 2013). After harvest (i.e., during
cold storage at 1°C) the carbohydrate status of the roots changed substantially. Starch
concentrations declined to <10% of their initial level. The degradation of starch in storage
organs such as tubers or roots is complex and not completely understood (Zeeman et al.,
2010). A range of enzymes may be involved in this process, including α-amylase and
β-amylase. In parsnip roots, α-amylase activity increased during cold storage and starch
degradation, whereas β- amylase activity did not change significantly. Concomitant with
the decrease in starch concentrations, sucrose concentrations increased markedly in
parsnip roots during cold storage.
This work confirms the existence of significant differences between storage
conditions and postharvest washing treatments with regarding to mass, dry matter content,
total sugar and carbohydrates constituents of parsnips during storage. Loss of mass and
quality change during storage was greater in the S-1 (simple cooling room) compared to
the S-2. This research revealed that pre-storage root washing (sodium hypochlorite or
hydrogen peroxide) significantly reduced weight loss and quality changes when compared
with a hot water treatment and un-washed roots.
CONCLUSIONS
All experimental results showed that parsnips can be stored for 6 months at
different storage conditions and in various postharvest treatments without showing a high
degree of quality loss. The results in the present study suggest that the best conditions are
671
storage in wooden pallets at 0°C with more than 95% of relative humidity. Parsnips in
5-kg perforated PE bags can be done for 3 weeks at 20°C during shelf life period (market
simulation).
Literature Cited
Bufler, G. and Horneburg, B. 2013. Changes in sugar and starch concentrations in parsnip
(Pastinaca sativa L.) during root growth and development and in cold storage. J. Hort.
Sci. Biotechnol. 88:756-761.
Correa, P.C., Farinha, L.R.L., Finger, F.L., Oliveira, G.H.H., Campos, S.C. and Bohelto,
F.M. 2012. Effect of physical characteristics on the transpiration rate of carrots during
storage. Acta Hort. 934:1341-1346.
Ilić, Z.S., Šunić, L., Barać, S., Stanojević, L. and Cvetković, D. 2013. Effect of
postharvest treatments and storage conditions on quality parameters of carrots
(Daucus carota L.). J. Agri. Sci. 5:100-106.
Israelsson, L. 2000. Handbok för Köksträdgården. Wahlström & Widstrand, Stockholm,
Sweden, p.289-299.
Kora, C., McDonald, M.R. and Boland, G.J. 2005. Occurrence of fungal pathogens of
carrots on wooden boxes used for storage. Plant Pathol. 54:665-670.
Seljåsen, R., Bengtsson G.B., Hoftun, H. and Vogt, G. 2001. Sensory and chemical
changes in five varieties of carrot (Daucus carota L.) in response to mechanical stress
at harvest and post-harvest. J. Sci. Food Agric. 81:436-447.
Shattuck, V.I., Kakuda, Y. and Yada, R. 1989. Sweetening of parsnip roots during short-
term cold storage. Can. Inst. Food Sci. Technol. J. 22:378-382.
Suojala, T. 2000. Variation in sugar content and composition of carrot storage roots at
harvest and during storage. Sci. Hort. 85:1-19.
Rutherford, P.P. 1977. Carbohydrate changes in stored vegetables with special reference
to red beet and parsnip. Ann. App. Biol. 85:440-444.
Toivonen, P.M.A. 2004. Parsnip. webpage, available at: http://usna.usda.gov/hb66/
103parsnip.pdf, Cited on 2008-03-18. Published in: The Commercial Storage of
Fruits, Vegetables and Florist and Nursery Stocks. USDA Agric. Hndbk. No.66.
Toivonen, P.M.A. 1992. The reaction of browning in parsnips. J. Hortic. Sci. 67: 547-551.
Zeeman, S.C., Kossmann, J. and Smith, A.M. 2010. Starch: its metabolism, evolution,
and biotechnological modification in plants. Annu. Rev. Plant Biol. 61:209-234.
Tables
Table 1. Effect of postharvest treatments and storage conditions on mass loss (%) from
first harvest date during storage period.
Storage condition
Begeč S-1 (0°C; >95% RH) Debeljača S-2 (0-2°C; <90% RH)
Storage days
60 120 180 60 120 180
Control 2.60a 5.66a 6.55a 14.67a 20.53b 22.19b
H2O2 2.95a 5.87a 7.73a 11.06b 22.16a 25.24a
NaOCl 3.67b 5.22a 8.57a 12.73b 20.29b 21.53b
Hot water 4.10b 6.20a 7.54a 15.27a 20.60b 23.00b
672
Table 2. Effect of postharvest treatments and storage conditions on mass loss (%) from
second harvest date during storage period.
Storage condition
Begeč S-1 (0°C; >95% RH) Debeljača S-2 (0-2°C; <90% RH)
Storage days
60 120 60 120
Control 4.46a 5.05a 9.42b 22.78b
H2O2 4.06a 4.78a 12.41a 26.00a
NaOCl 3.32b 4.71a 10.27b 21.46b
Hot water 3.55b 4.93a 13.46a 25.21a
Figures
Fig. 1. Effect of postharvest treatments and storage conditions on dry matter and total
sugar content during storage period.
673
Fig. 2. Effect of postharvest treatments and storage conditions on reducing and non-
reducing sugar content during storage period.
Fig. 3. Effect of postharvest treatments and storage conditions on sucrose, glucose and
fructose content during storage period.
674
A
B
Fig. 4. Staining for starch using Lugol solution in pieces of the cross-sections of parsnip
roots. Panel A, Lugol-stained pieces of cross-sections of parsnip root at harvest.
Panel B, Lugol-stained pieces of cross-sections of parsnip roots after 8 weeks in
cold storage (0°C).
Project
The aim of the study was to determine how different environmental control technologies (coloured shade-nets as net-house or plastic tunnels integrated with coloured shade-nets) could influence plan…" [more]
Project
The purpose of this study was to examine the effect of production systems – (organic-ORG orconventional-CONV) and growing season (autumn or spring) of cos lettuce (Lactuca sativa L. var. longi-foil…" [more]
Project
The purpose of this study was to examine the effect of production systems – (organic-ORG orconventional-CONV) and growing season (autumn or spring) of cos lettuce (Lactuca sativa L. var. longi-foil…" [more]
Project
The purpose of this study was to examine the effect of production systems – (organic-ORG orconventional-CONV) and growing season (autumn or spring) of cos lettuce (Lactuca sativa L. var. longi-foil…" [more]
Article
    The objective of this study was to develop postharvest techniques and technologies of the most important root vegetables: carrots, celeriac and parsnip. Investigations included the effect of harvest maturity (harvest at November or January) and postharvest washing treatments (hot water, H2O2 and NaOCl and non-washed-control) of carrots (Daucus carota ’Bolero F1’), parsnip (Pastinaca sativa... [Show full abstract]
    Article
    October 2016 · Acta horticulturae
      The purpose of this study was to examine the effect of harvest time (Novemberor January) and postharvest treatments (hot water, H2O2, NaOCl and non-washed –control) of celeriac (Apium graveolens var. rapaceum 'Mentor') on the changes in different storage conditions S-1 (0°C; >95% RH) or S-2 (0-5°C; 85-92% RH) during 180or 120 days of storage period (SP). At the end of SP the percentage water... [Show full abstract]
      Article
      October 2015 · Fresenius Environmental Bulletin · Impact Factor: 0.38
        The objective of this study was to determine the effect of harvest maturity and postharvest washing treatments (hot water, H2O2, NaOCl) and unwashing (control) on the nitrate content of carrots (Daucus carrota 'Maestro F1'), celeriac (Apium graveolens var rapaceum 'Mentor') and parsnip (Pastinaca sativa 'Banatski dugi') roots stored at 0±1 °C and >95% RH (S-1) or at 0-5 °C and 85-92% RH... [Show full abstract]
        Conference Paper
        June 2014 · Acta horticulturae
          The objective of this study was to determine the effect of harvest maturity and postharvest washing treatments (hot water, H2O2 and NaOCl) or without washing (control), on the nitrate content of carrots (Daucus carrota ‘Bolero F1’), celeriac (Apium graveolens var. rapaceum ‘Mentor’) and parsnip (Pastinaca sativa ‘Banatski dugi’) roots stored at 0±1°C and >95% RH (S-1) or at 0-5°C and 85-92% RH... [Show full abstract]
          Discover more