Research Article

1786
Table 2. Effects of bagging on sugar content in loquat fruit (mg g −1 )
www.soci.org H-X Xu, J-W Chen, M Xie
Cultivar Treatment Sucrose Glucose Fructose Sorbitol Total sugar
Baiyu CK 2.43 ± 0.04 b 29.0 ± 1.47 b 42.1 ± 2.14 b 2.26 ± 0.09 a 75.8 ± 3.71 b
OWPB 3.00 ± 0.04 a 36.7 ± 0.10 a 47.6 ± 0.40 a 2.59 ± 0.24 a 89.9 ± 0.53 a
TGDPB 2.27 ± 0.10 c 25.4 ± 1.34 c 42.3 ± 2.42 b 1.77 ± 0.10 b 71.8 ± 3.90 b
F-value 91.85 ∗∗∗ 76.17 ∗∗∗ 8.19 ∗ 19.77 ∗∗ 27.87 ∗∗∗
LSD0.05 0.14 2.29 3.76 0.32 6.24
Ninghaibai CK 1.59 ± 0.08b 39.7 ± 2.57a 51.7 ± 3.32a 3.42 ± 0.56a 96.4 ± 6.30a OWPB 2.26 ± 0.10a 40.8 ± 0.99a 52.8 ± 1.67a 2.40 ± 0.10b 98.2 ± 2.31a TGDPB 2.57 ± 0.34a 35.1 ± 1.52b 45.6 ± 0.82b 2.15 ± 0.19b 85.5 ± 2.01b F-value 17.03∗ 8.07∗ 9.27∗ 11.50∗∗ 8.70∗ LSD0.05 0.42 3.63 4.39 0.69 8.08
Values are expressed as means ± SD of three replications. Means within the same cultivar followed by the same superscript letters are not significantly
different at P = 0.05.
∗ Significant at P = 0.05.
∗∗ significant at P = 0.01.
∗∗∗ significant at P = 0.001.
CK, control (unbagged); OWPB, one-layered white paper bags; TGDPB, two-layered paper bags with a black inner layer and a grey outer layer.
OWPB or TGDPB, although the titratable acid content increased
significantly compared with Ninghaibai controls.
Surface colour is an important marketable (consumer acceptance)
quality attribute and is a measure of L ∗ , a ∗ , b ∗ and hab.
Table 1 shows that bagging improved fruit surface lightness as
L ∗ was higher in the bagged than in the control fruits of both
Baiyu and Ninghaibai. Fruit treated with TGDPB had the highest
lightness values. Reduced light is known to promote the degradation
of existing chlorophyll and inhibits carotenoid synthesis in
fruit peel, 26 and this resulted in unbagged fruits having a lower
hab and a more red than yellow hue (i.e. were more orange in
colour compared with bagged fruits). In addition, fruits treated
with TGDPB had higher hab than did those treated with OWPB.
The effects of bagging on sugar content
Sugar content is considered to be an important quality characteristic
of fresh fruit. However, bagging with different materials
can exert different effects on the composition of soluble sugars.
For example, Padmavathamma and Hulamani 23 found that total
sugars varied significantly with bag colour, whereas Yang et al. 27
observed that bagging tended to reduce sugar content slightly,
although the sugar content was not significantly affected by bag
type. Table 2 indicates that the effects of bagging type on sugar
content varied between cultivars. OWPB treatment increased the
sucrose, glucose, fructose and sorbitol content and significantly
increased the content of total sugar in Baiyu fruit. However, OWPB
treatment increased the sucrose content, did not affect the glucose,
fructose and total sugar content but decreased the sorbitol
content in Ninghaibai fruit. Total sugar contents in Baiyu and Ninghaibai
after TGDPB treatment were reduced by 5.6% and 11.3%,
respectively, as compared with the controls.
The effects of bagging on antioxidant compounds
and antioxidant capacity
Numerous studies have shown that fruit and vegetables are
sources of diverse nutrient and non-nutrient molecules, many of
which have antioxidant properties. The present study determined
the antioxidant capacities of loquat fruit and analysed fruit extracts
for compounds (total phenolic, flavonoid, carotenoid and vitamin
C) that might contribute to the antioxidant activity. Table 3 shows
that the total phenolic and flavonoid contents decreased after
bagging treatment. Following OWPB and TGDPB treatment, the
total phenolic content of Baiyu fruit was reduced by 9.5% and
45.6%, respectively, and that of Ninghaibai fruit was reduced by
5.0% and 26%, respectively. This indicates that bagging influences
the metabolism of phenolic compounds, of which the flavonoids
are the dominant family. The pattern of variation in flavonoid
content was similar to that observed for total phenolic, with
maximum levels occurring in unbagged Baiyu (28.2 ± 4.4 µgg −1 )
and Ninghaibai (51.0 ± 6.4 µgg −1 ) fruits. The flavonoid content
was also lower in TGDPB-treated fruits than in OWPB-treated fruit.
Carotenoids and vitamin C are also the antioxidant compounds
in loquat. The study found that the carotenoid and vitamin C
contents increased after bagging fruit with OWBP, but decreased
in fruit bagged with TGDBP. Our other experiments have also
observed that the carotenoid and vitamin C content varies
significantly with bag type; however, both decreased markedly
when light was excluded during the maturation of loquat as
compared with that of control fruit (data not shown).
Three independent methods, the DPPH, TEAC and FRAP assays,
were used to compare the antioxidant capacity of fruit extracts.
The results presented in Table 3 show that the antioxidant
potential of loquat fruit extracts was significantly affected by
light transmittance. The highest antioxidant potential in both of
Baiyu and Ninghaibai loquat fruits was under full sunlight and
lowest under bagging with TGDPB.
Table 4 indicates that the total phenolic content and antioxidant
capacity are well correlated (DPPH, r = 0.64; TEAC, r = 0.77;
FRAP, r = 0.90). Fruits with the highest phenolic content
(unbagged fruits of Baiyu and Ninghaibai) had the highest
antioxidant potentials whereas fruit extracts characterised by
low total phenolic levels exhibited a poor antioxidant capacity.
Numerous studies have reported similar linear relationships
between antioxidant activities and phenolic content. 28–30 A
good correlation was also observed between total flavonoid and
antioxidant capacity (DPPH, r = 0.84; TEAC, r = 0.87; FRAP, r =
0.99) (Table 4). Flavonoids are low-molecular-weight polyphenolic
compounds that are widely distributed in fruit and vegetables, 31
and many have been shown to have antioxidant 32 and anticancer
www.interscience.wiley.com/jsfa c○ 2010 Society of Chemical Industry J Sci Food Agric 2010; 90: 1783–1788