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Abstract

Biochemical changes in response to dehydration methods were investigated in basil leaf of variety Genovese. The leaf samples were dried by three methods viz. microwave, sun and tray (45°C, 50°C and 55°C) drying. Drying of basil leaves by all three methods resulted in the decline in ascorbic acid, phenolics, chlorophyll and antioxidative activity. Retention in ascorbic acid content was 27% in sun and tray (45°C) dried samples whereas it was 22.5% in microwave dried samples. Total soluble phenols, flavonoids, chlorophyll and antioxidant activity were highest in microwave dried samples followed by samples dried in tray dryer at 45°C. Increasing the temperature of tray dryer from 45°C to 55°C resulted in decline in all quality parameters. Sun drying resulted in minimum content of all these quality parameters. This research showed a possible use of microwave to dry basil leaves as it gave the best retention of basil quality and required shorter drying period as compared to sun and tray drying.
331
*Corresponding author : surekhabhatia@pau.edu
Date of receipt : 08.03.2018, Date of acceptance : 30.04.2018
Agric Res J 55 (2) : 331-335, June 2018
DOI No. 10.5958/2395-146X.2018.00059.5
Basil (Ocimum basilicum) is a culinary herb prominently
featured in Italian and South East Asian countries. Basil
is related to tropical regions of Asia particularly India and
Iran, but now it is widely available throughout the world.
Basil, being an aromatic herb, is used extensively in food to
add a distinctive aroma and avour. Fresh or dried leaves of
basil can be used as a spice. The use of basil in food is not only
for its avour and aroma, but also for other purposes such as
its antimicrobial, anti-inammatory, antioxidant, antiviral or
medicinal properties (Risch, 1997; Boateng, 2013). Major
aroma compounds from volatile extracts of basil had anti-
oxidative activity (Chairat et al., 2013). Basil contains a wide
range of essential oils rich in phenolic compounds (Hussain
et al., 2008) and other natural antioxidants including
polyphenols such as avonoids and anthocyanins (Kwee and
Niemeyer, 2011). Essential oils extracted from fresh leaves
and owers can be used as source of aroma additives in
cosmetics, pharmaceuticals and foods (Rocha et al., 2011).
Technological processes have important role in nal
product quality. Decrease of biological value of product
during application of technological processes is due to
instability of some biological components. Drying is widely
used method for preservation as the drying process inhibits
enzymatic degradation and limits microbial growth. Drying
methods also inuence the composition and biological activity
of plant (Ahrne et al., 2007). Variation in composition has
been reported in dierent leaves during drying (Ozcan, 2005;
Boudhrioua et al., 2009). Drying is reported to inuence the
volatile compounds present in basil. Decrease in the total
amounts of essential oils had been reported in sweet basil
during drying (Calín-Sánchez et al., 2012). The losses,
however, vary with the drying technique employed (Negi and
Roy, 2001). Dierent drying methods viz. air drying, vacuum
microwave drying, sun drying and oven drying have been
applied by various researchers (Di Cesare et al., 2003; Ozcan
et al., 2005), but the antioxidant capacity and associated
quality parameters in relation to drying methods are less
known. Therefore, it is important to nd best methods for
preserving the value of basil leaves. So, the present study was
undertaken to evaluate the eect of dierent drying methods
on biochemical quality parameters and antioxidant capacity
of basil leaf.
MATERIALS AND METHODS
The present investigation was carried out on basil variety
i.e. Genovese obtained from FieldFresh Pvt. Ltd. Laddowal,
Ludhiana. Leaves of basil were carefully cleaned manually
to remove dirt and damaged ones removed from stalk and
were surface sterilized by washing with tap water. The leaf
samples were dried in microwave, sun ((12.2-21.0°C, 37-
98% humidity) and in tray dryer at three temperatures viz
45°C, 50°C and 55°C(Calín-Sánchez et al.,2012). The drying
conditions in each of these methods was such as to maintain
the moisture content of less than 10% (Farias, 2003; Oladele
and Aborisade, 2009). Dried basil leaves were then analyzed
for dierent quality parameters.
Estimation of ascorbic acid
Ascorbic acid was estimated by method described by
AOAC (1984). Basil leaves (0.5 g) were crushed in pestle
and mortar using 10 ml of metaphosphoric acid-acetic acid
solution and was ltered. Then 5 ml of ltered extract was
titrated against dye till the appearance of light pink colour
and the volume of dye used to oxidize vitamin C in sample
was noted. Ascorbic acid content was calculated by titration
of the standard ascorbic acid (0.2 mg/ml) with dye.
EFFECT OF DRYING METHODS ON BIOCHEMICAL QUALITY OF BASIL LEAF
Rudrakshi Sharma1, Surekha Bhatia2* and Preetinder Kaur2
1Department of Biochemistry, 2Department of Processing and Food Engineering
Punjab Agricultural University, Ludhiana-141004, Punjab
ABSTRACT
Biochemical changes in response to dehydration methods were investigated in basil leaf of variety Genovese. The
leaf samples were dried by three methods viz. microwave, sun and tray (45°C, 50°C and 55°C) drying. Drying of
basil leaves by all three methods resulted in the decline in ascorbic acid, phenolics, chlorophyll and antioxidative
activity. Retention in ascorbic acid content was 27% in sun and tray (45°C) dried samples whereas it was 22.5%
in microwave dried samples. Total soluble phenols, avonoids, chlorophyll and antioxidant activity were highest
in microwave dried samples followed by samples dried in tray dryer at 45°C. Increasing the temperature of tray
dryer from 45°C to 55°C resulted in decline in all quality parameters. Sun drying resulted in minimum content of
all these quality parameters. This research showed a possible use of microwave to dry basil leaves as it gave the
best retention of basil quality and required shorter drying period as compared to sun and tray drying.
Key words: Antioxidative activity, Ascorbic acid, Basil, Chlorophyll, Drying methods, Phenolics
332
Estimation of chlorophyll
Chlorophyll was extracted and estimated as described by
Sozzi et al. (1998). Basil leaves (0.5 g) were crushed in pestle
and mortar and chlorophyll was extracted ve times using
10ml of acetone. The extract was covered with aluminium
foil to prevent photo-bleaching. Combined mixture was
nally placed on shaker at 140 rpm for 30 minutes and then
centrifuged at 12000 rpm for 15 minutes. Final volume
of supernatant was made to 100ml by adding acetone.
Chlorophyll content was determined by taking absorbance
at 644.8 nm and 663 nm. The total chlorophyll content was
estimated according to the formula below
Total chlorophyll (mg/g tissue) = 20.7(A644.8)+8.02(A663)
xV/1000xW
Where A ; absorbance at specic wavelength, V; nal
volume of chlorophyll extract in acetone, W; weight of tissue
Estimation of phenolic compounds
Basil leaves (1g) were crushed and reuxed with 5 ml
of 80% methanol for 1h. The reuxed sample was ltered
through Whatman lter paper No.1 and the volume was made
10 ml by washing with hot 80% methanol. The extract, thus
prepared was used for estimation of phenolic compounds.
Total phenols were estimated as described by Singleton et
al. (1999). Methanolic extract (0.5ml) was evaporated to
dryness and the residue was dissolved in 6.5 ml of distilled
water. To this, 0.5ml of Folin’s reagent was added and shaken
thoroughly. After 5min, 1 ml of saturated solution of Na2CO3
was added and the reaction mixture was incubated for one
hour at room temperature. The absorbance of blue colour
was read at 760 nm against a blank. The concentration of
total phenol was determined from standard curve prepared
simultaneously using gallic acid (10-50µg/ml). Estimation
of total soluble avonoids was done by method described
by Balabaa et al. (1974). Methanolic extract (3ml) was
evaporated to dryness and the residue left was dissolved in
10 ml of 0.1 M methanolic solution of aluminum chloride.
Intensity of yellow colour so developed was read at 420 nm
against blank. Concentration of total soluble avonoids was
determined from standard curve prepared simultaneously
using rutin (40-200 µg/ml).
Estimation of total antioxidant activity
Total antioxidant activity was estimated as described by
Dasgupta and De (2006). To one g of crushed basil leaves, 10
ml of distilled water was added. Sample was boiled for 1h in
boiling water bath and left overnight. To 2 ml of above extract,
one ml of TAA (0.6 M H2SO4, 28mM sodium phosphate and
4mM ammonium molybdate, mixed in equal amounts before
use) reagent was added and mixture was incubated at 95°C
for 90 min. After cooling, intensity of blue colour was read
at 695 nm. The total antioxidant activity was measured as
ascorbic acid equivalent and was determined from standard
curve prepared simultaneously using ascorbic acid (40-200
µg/ml).
Statistical analyses
All experiments were carried out in triplicates. Standard
error was calculated manually for all experiments. Data
were subjected to one way ANOVA along with the multiple
comparisons by Tukey’s test (Graphpad Software Inc. USA).
RESULTS AND DISCUSSION
Drying time
In sun drying, time taken to dry the leaves was 70h and
during this time, weight of basil leaves was reduced by 92%.
Microwave drying took 7 minutes 30 seconds for reducing
the weight by 91.4% of fresh weight. Tray drying took 10 h
to reduce the physiological weight by 90%, 91% and 91.3%
at 45°C, 50°C and 55°C, respectively (Table 1). All the leaves
were dried to approximately 4% moisture content.
Table 1. Time taken for drying and physiological weight loss of
basil leaves
Methods of drying Drying time Physiological loss
in weight (%)
Sun drying 70 hrs 92.0±0.65
Tray drying at 45°C 10 hrs 90.0±0.42
Tray drying at 50°C 10 hrs 91.0±0.59
Tray drying at 55°C 10 hrs 91.3±0.48
Microwave drying 7 min 30 sec. 91.4±0.24
The values are mean ± SE of three determinations
Ascorbic acid
Drying of basil leaves resulted in signicant losses in
ascorbic acid content. The ascorbic acid content in control
was 766 mg/100g (db). After drying, the ascorbic acid was
found maximum in sun dried samples i.e. 207.45 mg/100g,
followed by tray drying at 45°C i.e. 206.28 mg/100g. Least
ascorbic acid content was found in microwave dried leaves
i.e. 172.48 mg/100g. Temperature of tray drying also had
signicant eect on ascorbic acid content as it decreased
signicantly with the increase in temperature during tray
drying. Ascorbic acid content reduced to 183.73 and 158.65
mg/100g at drying temperature of 50°C and 55°C (Fig.1a)
respectively. Decrease in ascorbic acid during drying might
be due to its oxidation at high temperature resulting in
decomposition of vitamin C. Oladele and Aborisade (2009)
reported 43-48% reduction in ascorbic acid content of Indian
spinach leaves during drying by dierent methods. Oboh
and Akindahunsi (2004) also found signicant decrease in
ascorbic acid content of some sun dried leafy vegetables
although they did not investigate other drying techniques.
Total phenolics
In fresh basil leaf samples phenol and avonoid content
was 2927.00 and 3091.98 mg/100g (db), respectively.
Method of drying signicantly inuenced the total phenolic
content of dried basil leaves. After drying, total soluble
333
phenol content was found highest in microwave drying i.e.
174.91 mg/100g and lowest in tray drying at 55°C i.e. 88.32
mg/100g, respectively. Leaves dried in tray dryer at 45°C had
149.01 mg/100g of total soluble phenol, whereas in sun dried
samples phenol content was found to be 96.02 mg/100g.
Temperature of tray drier also had signicant eect on the
phenol content as it decreased with increase in temperature
of tray dryer i.e. it reduced to 95.43 and 88.32 mg/100g at
drying temperature of 50°C and 55°C respectively (Fig. 1b).
Similar to phenol content, avonoid content was also found
Fig.1. Eect of drying methods on (a) ascorbic acid content (b)
total soluble phenols (c) total avonoids (The values are
mean ± SE of three determinations. Values with the same
letter were not signicantly dierent and values with the
dierent letter were signicantly dierent according to
the Tukey test (p<0.05))
maximum in microwave dried samples (160.85mg/100g)
followed by tray dried samples at 45°C (158.45 mg/100g)
and least in leaves dried in sun (114.32mg/100g) (Fig.1c).
Our ndings are similar to the data from a previous study by
Miean and Mohamed (2001) and Erbay and Icier (2009) who
reported a decreased in avonoid and phenol content in holy
basil and olive leaves after thermal processing.
Chlorophyll
Drying of basil leaves in microwave drying found no
signicant change in chlorophyll content as it reduced from
32.4 mg/g (db) in fresh leaves to 31.8 mg/g in microwave
dried basil leaves whereas, during other drying methods
signicant reduction in chlorophyll content was found.
During tray drying, it reduced to 17.5, 15.7 and 14.2 mg/g
at 45°C, 50°C and 55°C respectively. Lowest chlorophyll
content i.e.12.4 mg/g was found in sun dried samples (Fig.
2a). Change in content of chlorophyll during drying had
been reported by Di Cesare et al. (2003). According to them,
intracellular spaces of leaf collapsed during heating of leaf
resulting in release of chlorophylls from the protein complex.
Fig. 2. Eect of drying methods on (a) chlorophyll content (b)
total antioxidant activity (The values are mean ± SE of
three determinations. Values with the same letter were
not signicantly dierent and values with the dierent
letter were signicantly dierent according to the Tukey
test (p<0.05))
(a)
(b)
(c)
(a)
(b)
334
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These events promoted the change of chlorophylls into
pheophytins, providing a substrate for enzymatic browning.
It was also reported that the method used to dry fruits and
vegetable materials signicantly aected the three colour
parameters with air drying causing extensive browning
(Krokida et al., 2001). Microwave drying allowed a larger
retention of chlorophyll pigments thereby, preserving the
colour of fresh basil leaves.
Antioxidant activity
In fresh basil leaves total antioxidant activity was 3091.4
ascorbic acid equivalent. After drying total antioxidant
activity was also found to be maximum in microwave
drying i.e. 197.47 mg/100g followed by tray drying i.e.
174.39 mg/100g and least in sun drying 98.66 mg/100g
(Fig.2b) which was similar to trend followed for phenols
and avonoids and opposite of ascorbic acid. This suggested
that the antioxidant activity of basil leaf was not mainly
contributed by phenolics and not by ascorbic acid. Higher
retention of the quality parameters of leafy green vegetables at
faster drying conditions had also been reported earlier (Negi
and Roy, 2001). Phenolic compounds are commonly found in
plants and they had been reported to have strong antioxidant
activities (Bors et al., 2001; Li et al., 2006). Decrease of
antioxidant activity might be due to thermal degradation of
phenolic compounds. It could also be explained by loss of
antioxidant enzyme activities and activity of degradative
enzymes (Lim and Murtijaya, 2007).
This research showed that biochemical quality of basil
leaves was inuenced by the method of drying and a possible
use of microwave to dry basil leaves. Microwave dried basil
leaves showed larger retention of chlorophyllic pigments,
phenolic compounds as well as total antioxidant activity when
compared to leaves dried by traditional drying techniques i.e.
sun drying. Moreover microwave drying required shorter
period as compared to sun drying and oven drying.
Authors’ contribution
Conceptualization and designing the research work (SB,
PK); Execution of Lab experiment and data collection (RS);
Analysis of data and interpretation (SB, RS, PK); Preparation
of manuscript (SB, RS)
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... Total soluble phenolic content was decreased when leaves dried at 45°C, comparing to fresh holy basil phenolic and flavonoid contents being 2,927.00 and 3,091.98 mg 100 g -1 dry weight (Rudrakshi, Surekha and Preetinder, 2018). Zafer and Filiz (2009) reported that oleuropein in olive leaves could be hydrolyzed to hydroxytyrosol, in addition thermal drying treatment induced deterioration of the phenolic. ...
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... For example, there exist studies on the effects of different drying methods (microwave, sun-drying at 12.2-21.0 • C and 37-98% humidity, and machine-drying (MD) at 45, 50, or 55 • C) on ascorbic acid, phenol, and chlorophyll contents and antioxidant activity [14]; and optimization of osmotic dehydration to improve dried product quality and to limit changes in appearance, texture, flavor, and color [15]. We have previously examined the tea-making process of ...
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Agriculture and Food Science Book series aims to bring together leading academic scientists, researchers and research scholars to publish their experiences and research results on all aspects of Agriculture and Food Science. It also provides a premier interdisciplinary platform for researchers, practitioners and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the fields of Agriculture and Food Science. High quality research contributions describing original and unpublished results of conceptual, constructive, empirical, experimental, or theoretical work in all areas of Agriculture and Food Science are cordially invited for publication. It also focuses on a range of issues but not limited to 1. Textile Engineering 2. Agronomy 3. Soil Science 4. Microbiology 5. Phsiology 6. Ecology 7. Epidemology 8. Genetics & Plant Breeding 9. Plant Pathology 10. Entomology 11. Agricultural Biotechnology 12. Environmental Sciences 13. Agricultural Engineering 14. Food Science 15. Waste Management 16. Animal Husbandry and Dairying 17. Agricultural Statistics 18. Food Storage and Preservation 19. Food Technology and Processing 20. Agricultural Sustainability 21. Irrigation 22. Root Morphology Sensing 23. Yield-Monitoring 24. Industrial Crops and Products Engineering 25. Artificial Intelligence in Agriculture 26. Poultry Science 27. Forestry 28. Horticulture 29. Fisheries Science 30. Agriculture Equipments & Smart Technologies 31. Veternary Sciences 32. Contract & Integrated Farming 33. Sericulture
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Publisher Summary This chapter discusses the analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Analyses of the Folin-Ciocalteu (FC) type are convenient, simple, and require only common equipment and have produced a large body of comparable data. Under proper conditions, the assay is inclusive of monophenols and gives predictable reactions with the types of phenols found in nature. Because different phenols react to different degrees, expression of the results as a single number—such as milligrams per liter gallic acid equivalence—is necessarily arbitrary. Because the reaction is independent, quantitative, and predictable, analysis of a mixture of phenols can be recalculated in terms of any other standard. The assay measures all compounds readily oxidizable under the reaction conditions and its very inclusiveness allows certain substances to also react that are either not phenols or seldom thought of as phenols (e.g., proteins). Judicious use of the assay—with consideration of potential interferences in particular samples and prior study if necessary—can lead to very informative results. Aggregate analysis of this type is an important supplement to and often more informative than reems of data difficult to summarize from various techniques, such as high-performance liquid chromatography (HPLC) that separate a large number of individual compounds .The predictable reaction of components in a mixture makes it possible to determine a single reactant by other means and to calculate its contribution to the total FC phenol content. Relative insensitivity of the FC analysis to many adsorbents and precipitants makes differential assay—before and after several different treatments—informative.
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Sun drying and oven drying (50 °C) characteristics of basil (Ocimum basilicum L.) were determined. The effect of these drying methods on the mineral content of fresh, oven dried and the wire basket sun dried basil were compared. Oven drying resulted in increased drying rates and shorter drying time. Basil can be oven dried at 50 °C to 17.31% moisture content after 15 h and can be sun dried to 23.79% moisture content after 28 h. The mineral content of oven dried herbs was higher than sun dried herbs. K, P, Ca, S, Mg, Fe and Al contents were determined as main minerals in both oven and sun dried basil.
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This study reports the effects of drying methods on nutrient retention in a leaf vegetable during storage. The leaves of Indian Spinach were dried to 3.50-4.0% moisture content in the sun (35°), shade (28°C) and oven (45°C) and then stored in polyethylene wrappers. Their moisture, ascorbic acid, minerals and total chlorophyll contents were determined after drying and during storage. There was minimal moisture gain during the twelve week storage period being less than 1% in all three drying methods. Ascorbic acid decreased by 43-48% as a result of drying but storage for twelve weeks did not result into much further loss. Shade-dried leaves retained ascorbic acid in the least. Chlorophyll and minerals contents also decreased slightly with drying and storage. Shade-dried leaves were lowest in Ca, Mg, K, Na, Fe, Mn and Zn. The contents of Ca and Mg in shade dried leaves increased in storage while K, Mn and Zn decreased. Manganese was the most critically reduced element by both drying and storage with shade dried leaves losing 73.2, 81.6% at drying and 12 weeks later. Comparative figures for sun and oven dried leaves were 49.2, 47.6, 50 and 62.6% for the same periods. The greatest reduction in Zn content also occurred with shade drying. Sun drying resulted into more nutrient retention while there was only marginal difference in ascorbic acid content by the three techniques. Chlorophyll content was not much affected by both drying and storage and shade dried leaves retained chlorophyll more than those dried in the sun and oven.