3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P24 INFLuENCE OF LONG-TERM STORAGE
CONDITIONS ON ANTIOxIDANT AND
OThER ACTIVE COMPONENT CONTENT IN
SEVERAL SORTS OF APPLES
KATEřInA DUROňOVá a , KATEřInA PAřILOVá a ,
AnDREA HALIEnOVá a , JITKA DVOřáKOVá a ,
RADKA KOČí a , JAn GOLIአb and IVAnA MáROVá a
a Institute of Food Science and Biotechnology, Brno University
of Technology, Purkyňova 118, 612 00 Brno, Czech
Republic,
b Department of Post-Harvest Technology of Horicultural
Products, Valtická 337 691 44 Lednice, Czech Republic,
katka.duronova@centrum.cz
Introduction
Apples are one of the most common sources of natural
antioxidants in Czech population. This work was focused on
study of changes of antioxidant content, enzyme activities,
and protein composition in several local sorts of apples stored
for a long time under controlled atmosphere with reduced
oxygen content.
To qualitative as well as quantitative analysis of individual
low-molecular weight antioxidants RP-HPLC/UV-VIS
and LC/MS were used. Activites of superoxide dismutase,
peroxidase and polyphenoloxidase were measured spectrophotometrically,
antioxidant activity was measured by Randox
kit. Proteins were analyzed by 1D microfluidic system
Experion, saccharides by HPLC/RI. Except long-term storage
conditions also influence of some other commonly used
technological processes were tested (freezing, drying).
Material and Methods
P l a n t M a t e r i a l
Apples of three cultivars (Idared, Golden Delicious and
Jonagored) were harvested and stored under Regular Atmosphere
(RA) and controlled atmosphere-Fluctuated Anaerobiosis
(FAn) for 158 days at 1 °C.
T o t a l P h e n o l i c , F l a v o n o i d a n d
A n t i o x i d a n t C a p a c i t y A s s a y s
Total solube phenolics were analyzed colometrically
with Folin Ciocalteu reagent using photometric detection
(750 nm) and results were expressed as mg gallic acid per
1 g of apple.
Total flavonoid content was analyzed colometrically
with nanO 2 + AlCl 3 using photometric detection (510 nm).
Results were expressed as mg catechin per gram of apple tissue.
Total antioxidant capacity was measured by Randox kit.
This colorimetric method use radical ABTS˙ + (2,2’-Azinobis(3-ethyl-2,3-dihydroBenzoThiazol-6-Sulphonate))and
photometric detection (600 nm). Results were expressed as
mmol Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic
acid) per liter of raw apple juice.
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I n d i v i d u a l A n t i o x i d a n t s A s s a y s
Individual flavonoids were analyzed using RP- HPLC
method with the extrenal standarts ((–)catechin, catechin
gallate, chlorogenic acid, epicatechin, morin, phlorizin, quercetin,
rutin). Spectrophotometric detection (UV-VIS) after
their extraction was used. In these assays two types of extrac-
tion were used:
•
•
water extraction
extraction by mixture of 1% HCl + ethylacetate
Samples (20 μl) were injected into the RP-18 column
(Biospher PSI 200 C18, 7 μm, 150 mm × 4.6 mm). Mobile
phases were methanol/water (55 : 45) for water extraction
and methanol/acetonitrile/water with 1% phosporic acid
(20 : 30 : 50) for organic extration. The flow rate was maintained
at 0.75 ml min –1 , analysis was performed at 30 °C.
Carotenoids (beta-carotene, lycopene, luteine) were
analyzed by RP-HPLC with spectrophotometric detection,
organic extraction (acetone + diethylether) was used for pigment
isolation. Samples (20 μl) were injected into the RP-18
column (Hypersil C18, 5 μm, 250 mm × 4.6 mm). As mobile
phase for isocratic elution methanol was used. The flow rate
was 1.1 ml min –1 , analysis was done at 45 °C.
A s c o r b i c A c i d A s s a y
Ascorbic acid was determined using RP-HPLC on
Hypersil APS-2, nH 2 , 5 μm, 150 mm × 4.6 mm column. Samples
were stabilized by 2% HPO 3 , 20 μl was injected. Mobile
phase was natrium acetate/acetonitrile (95/5). Analysis was
performed at flow rate 0.6 ml min –1 and 30 °C.
Microtitration method with 2,6-dichlorindofenol was
used as comparative method too. The end point of titration
was determined by pink colour.
Results were expressed as mg of ascorbic acid per kg
of apples.
S u r f a c e M i c r o f l o r a A s s a y
natural microflora was determined using Evirocheck ®
kit (Merck). Two types of kit were used:
•
•
Contact TVC – Total Viable Counts
Contact YM(R) – Yeasts and Mould
These tests can be used for analysis of liquid material
as well as for surface testing. Results were expressed as
KBE cm –2 or cfu cm –2 . Artificial injection of Gloeosporium
and Penicillium moulds was done for comparison of effect
of surface infection on apple quality. Infected apples were
stored in darkness and cold (6 °C). After 4–8 weeks surface
changes were observed and surface microscopy of apples was
done too.
S e n s o r y A n a l y s i s
A group of 21 respondents were enrolled into orientation
sensory study. They tested several apple varieties and evaluated
basic sensory parameters. Apple variety preferences
and apple intake was studied too. The group of respondents
was divided into two age-different groups: