3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P65 FAT CONTENT AND ITS QuALITy IN
RAPESEED (brAssiCA NAPus L) DuRING
STORAGE
Ján MAREČEK, MARTInA FIKSELOVá, HELEnA
FRAnČáKOVá and ZDEnKA MUCHOVá
Department of Plant Processing and Storage, Faculty of Biotechnology
and Food Sciences, Slovak University of Agriculture,
Tr. A. Hlinku 2, Nitra, 949 76 Slovakia,
Jan.Marecek@uniag.sk
Introduction
Fats and oils contain unsaturated fatty acids bound with
triacyglycerols. Plant oils consist of polyunsaturated fatty
acids which are susceptible for oxidation (Pokorný, 2001).
Colza oil is low in saturated fatty acids content (6–8 %),
but is source of linolenic acid, oleic acid (60 %), and has
favourable ratio of n-3 and n-6 fatty acids.
By the influence of higher temperatures the fat is decomposed.
Chemical and physical changes of fat during frying
cause an increase of fat viscosity, free fatty acids content,
color changes, decrease of iodine value, and tendency to foaminess
of fat (Venskutonis et al., 2000, Salková, 2002).
The aim of this work was evaluation of the influence of
storage time on fat stability in rapeseed (oxidation changes
of fat fraction).
M a t e r i a l a n d M e t h o d s
Rapessed was stored in silo. Samples (15 kg) were continuosly
taken and analysis were performed - at the begining
of storage (after harvest), during the storage and at the end
of storage time. Rapeseed was stored in Poľnonákup Hont in
Hontianske nemce, as the mixture of variants. Analysis were
performed at Department of Plant Processing and Storage,
Faculty of Biotechnology and Food Sciences (SUA nitra),
then at Slovak Agricultural Research Centre in nitra and
at Food Research Institute, Biocenter Modra. Results are present
from 3 years of observations (2003–2005).
M e t h o d s
Determined parameters of the rapeseed quality were the
content of dry matter by Slovak Technical Standard (STS
560116), ash content (combustion at 900 °C), fat content
(STS 560116), peroxide value (STS 580130), iodine value
(by Hanuš), acid value (STS 580130), thiobarbituric value
(distilling method), nitrogen compounds (by Kjeldahl). Fatty
acids representation (chromatographically) was determined
as follows: myristic, palmitic, palmitoleic, stearic, oleic, linoleic,
linolenic, arachidonic, behenic and erucic.
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•
•
Terms of samplings:
year 2003:1 st July 10, 2003, 2 nd October 12, 2003,
3 rd January 15, 2004, 4 th April 20, 2004
year 2004: 1 st August 23, 2004, 2 nd October 28, 2004, 3 rd
January 24, 2005, 4 th April 20, 2005
year 2005: 1 st August 10, 2005, 2 nd november 15, 2005,
3 rd February 15, 2006, 4 th May 20, 2006
s718
Results and Discussion
Mean dry matter content varied from 94.34 % (2005) to
94.81 % (2003). Higher content of dry matter is important
point for storage stabilize. In term of rapeseed storage it is
important to take into account that water is situated in the
hydrophilic part of the seeds, in the direction to the skin. In
the middle of the seed there is the fat.
nutritional compunds were found to be stabile. Mean
nitrogen compounds were determined more than 22.42 %.
Mean ash content of the rapeseed was 3.83 %, ranged from
3,65 (2004)–3,93 % (2003).
E v a l u a t i o n o f O x i d a t i v e C h a n g e s
i n L i p i d F r a c t i o n o f R a p e s e e d
Mean fat content ranged from 43.16 (2003) to 45.52 %
(2004). Linhart (2006) declared that colza oil was for its
benefits on immune system evaluated more favourable than
the rest of edible oils. Biodiesel production from rapeseeds
makes this more preferable compared to another oils. Both
advantages increased the price of rapeseed.
Peroxide value is optimal up to 10 mmol O 2 kg –1 .
Our mean results showed 2.4 mol O 2 kg –1 . Acid value was
more than 2 mg KOH g –1 of fat (2.28 mg KOH g –1 fat).
According to the STS (46 2300-2) acidity of rapeseed during
the storage got higher during the years 2004–2005. Higher
content of free fatty acids can cause problems with oil refining.
Mean iodine value was 102.3, then this fat can be classified
as semi-drying. Thiobarbituric value is desired to be low
Table I
Oxidative changes of lipid fraction of rapeseed during the
storage
Peroxide
Thiobarbituric
Rape Fat value Acid value
seed [%]
[mg KOH g –1 value
[mmol ] [mg
O2 kg –1 ] MDA kg –1 ]
2003
1. 39.83 2.90 1.77 0.081
2. 44.83 3.71 1.75 0.088
3. 44.80 3.87 1.77 0.092
4. 43.16 3.85 1.79 0.096
Mean 43.16 3.58 1.77 0.089
2004
1. 45.20 1.82 2.02 0.058
2. 44.18 2.21 3.19 0.056
3. 46.50 3.08 3.09 0.066
4. 46.20 3.75 3.20 0.063
Mean 45.52 2.72 2.86 0.061
2005
1. 42.63 1.72 1.95 0.043
2. 43.60 1.95 1.95 0.051
3. 44.15 1.98 2.42 0.056
4. 44.26 2.24 2.52 0.064
Mean 43.66 1.97 2.22 0.053