Abstract The aim of this study is to evaluate the quality properties of raspberry and peach jams during storage. Jams were prepared with a reduced amount of sucrose, citric acid and low-estrified pectin with the addition of calcium ions in the form of calcium citrate. Physico-chemical parameters, such as total dry matter, soluble solids, sugars, total acids, pH, vitamin C, fats, proteins and ash after storage of 15 and 90 days were tested. The jams were exposed to microbiological analysis also. Results showed that the values of ash, fats and vitamin C were not changed regardless the storage period of the analysed raspberry and peach jams. The period of storage increased the values of total dry matter from 44.97% to 45.86%, soluble solids from 40.17 °Brix to 41.5 °Brix and total acids from 1.47% to 1.49% in raspberry jam. In peach jam these results changed from 42% to 44.1%, from 41.92 °Brix to 42.9 °Brix, and from 0.92% to 0.97% respectively. Microbiological examinations indicate that jams are microbiologically proper according to standards. From the overall results it can be concluded that the storage period has effect on the prepared raspberry and peach jams, but their quality remains good and has maximum consumer acceptance

Gjore Nakov

Ljubica Karakashova

Ljupka Necinova

Marija Menkinoska

Naiden Delchev

Tatjana Blazevska

Valentina Pavlova

Viktorija Stamatovska

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Journal of Hygienic Engineering and Design
25
Original scientific paper
UDC 664.858:634.711
           664.858:634.25
STORAGE IMPACT ON THE QUALITY OF RASPBERRY AND PEACH JAMS
Valentina Pavlova1*, Ljubica Karakashova2, Viktorija Stamatovska1, Naiden Delchev3, Ljupka 
Necinova1, Gjore Nakov1, Marija Menkinoska1, Tatjana Blazevska1
1Faculty of Technology and Technical Science - Veles, St. Kliment Ohridski University - Bitola, 
Petre Prlickov 42, 1400 Veles, Republic of Macedonia
2Faculty for Agricultural Sciences and Food, Ss. Cyril and Methodius University, 
Edvard Kardelj bb, 1000, Skopje, Republic of Macedonia
3Department of Analytical Chemistry, University of Food Technologies, 26 Maritza Blvd., 
4002 Plovdiv, Bulgaria
*e-mail: valentina.pavlova2@gmail.com
Abstract
The aim of this study is to evaluate the quality proper-
ties of raspberry and peach jams during storage. Jams 
were prepared with a reduced amount of sucrose, citric 
acid and low-estrified pectin with the addition of calci-
um ions in the form of calcium citrate. Physico-chemical 
parameters, such as total dry matter, soluble solids, 
sugars, total acids, pH, vitamin C, fats, proteins and ash 
after storage of 15 and 90 days were tested. The jams 
were exposed to microbiological analysis also. 
Results showed that the values of ash, fats and vitamin 
C were not changed regardless the storage period of 
the analysed raspberry and peach jams. The period of 
storage increased the values of total dry matter from 
44.97% to 45.86%, soluble solids from 40.17 °Brix to 
41.5 °Brix and total acids from 1.47% to 1.49% in rasp-
berry jam. In peach jam these results changed from 
42% to 44.1%, from 41.92 °Brix to 42.9 °Brix, and from 
0.92% to 0.97% respectively. Microbiological examina-
tions indicate that jams are microbiologically proper 
according to standards.
From the overall results it can be concluded that the 
storage period has effect on the prepared raspberry 
and peach jams, but their quality remains good and 
has maximum consumer acceptance.
Keywords: Raspberry jam, Peach jam, Quality properties, 
Storage period. 
1. Introduction
Fruits are important source of energy for human beings 
with availability only during specific season. People of 
all age groups liked them. Due to high water or juice 
contents, they are perishable. Preparation of juice, jam, 
jelly, marmalade etc. increase the shelf life of fruits al-
lowing access to consumers all year round. 
Jam is made by boiling fresh, frozen or chemically 
half-processed canned fruit by adding sugar, pectin 
and acid. The adequate texture requires a correct com-
bination of each components. The main feature of this 
product is that it contains fruit pieces in an even gel 
substance, without separating the fruit juice [1].
Jams can last for extremely long periods of time. Several 
types of jams have been studied with regard to the in-
fluence of storage time on their quality. Muhamed et 
al. [2] prepared mango jams from different margo vari-
eties and analyzed for physicochemical, microbial and 
sensory parameters at 30 days storage interval for 150 
days. It was concluded that good quality mango jam 
from different mango varieties could be prepared and 
stored at ambient temperature for 150 days with mini-
mum damage to the product quality. 
Rehman et al. [3] evaluated the quality of strawber-
ry jam during storage. The physico-chemical analysis 
were studied at interval of 15 days for a total period of 
sixty days. The jam samples were also organoleptically 
evaluated. The evaluation showed that the prepared 
strawberry jam was of good quality and had maximum 
consumer acceptance. Imtiaz and Iftikhar [4] used in-
digenous varities of apricot and apple to made jams 
with different formulation. These formulations were 
stored for 60 days at ambient temperature, and eval-
uated for chemical and organoleptic properties. The 
results showed that all the formulations remained ac-
ceptable for 60 days at ambient temperature. 
Journal of Hygienic Engineering and Design
26
Vidhya and Anandhi [5] studied fruit bar and jam from 
wood apple and compared their quality parameters 
during different periods of storage up to 90 days. The 
storage stability was good in both jam and fruit bar 
with respect to flavour and consistency and they ware 
safe and fit for consumption. Another study [6] focused 
on the quality attributes of stored Roselle jam from dark 
and light red varieties. The jams were stored at ambient 
and cold temperatures and at two weeks interval they 
were evaluated for pH, titratable acidity, Vitamin C, ash, 
dry matter, moisture content and sensory properties 
for a period of six weeks. It was found that prepared 
Roselle jams stored for six weeks at ambient and cold 
temperatures were still acceptable.
In Macedonia many fruits are grown. Although most 
of them are marketed fresh, they can be used to make 
jams. This study attempted to produce raspberry jam 
and peach jam with a reduced amount of sucrose and 
assess their quality characteristics during storage at 
ambient temperature.
2. Materials and Methods
For preparation of jams, cultivated raspberry 
Willamette from Krusevo region and the cultivated 
peach Cresthaven from Rosoman were used. The man-
ufacture of jams, by using traditional technological 
methods od procesiing was performed at the factory 
Vitalia Nikola Ltd., Skopje. Jams were prepared with 
a reduced amount of sucrose. To achieve the desired 
texture during the production process, a low-ester-
ified pectin from the GENU pectin type LM 115AS by 
CPKelco with the addition of calcium ions in the form 
of calcium citrate was added. The necessary acidity was 
provided using citric acid.
The technological procedure comprises the following 
operations: washing and inspection, boiling by add-
ing a sucrose while stirring continuously, adding pec-
tin, calcium citrate and acid, mixing, filling in jars and 
closing. The jam simples were cooked in the open inox 
kettle. The percentage of dry matter during the pro-
duction process has been controlled by a refractome-
ter. The processed jams were packed into glass jars and 
stored at ambient temperature.
The produced jams were tested for their physico-chem-
ical composition and microbiological safety after stor-
age of 15 and 90 days.
The physico-chemical composition was estimated by 
determination of: total dry matter by oven drying at 
105 0C, content of total soluble solids by means of a 
refractometer, a gravimetric determination of ash in a 
muffle furnace at 550 0C, total acidity by titration of a 
solution of NaOH with concentration of 0.1 mol/L, the 
pH value with a pH meter, determination of sugars with 
the HPLC-RI method, vitamin C with an iodometric ti-
tration method, fats with the Soxhlet method and pro-
teins with the Kjeldahl method.
The microbiological tests have been made in order 
to confirm the microbiological safety of the jams pro-
duced.
3. Results and Discussion
The data on physico-chemical analysis of the produced 
jams after storage of 15 and 90 days are presented in 
Figure 1 – 3 and in Table 1.
44,97
40,17
45,86
41,5
42
41,92
44,1
42,9
35 40 45 50
15 days 
Raspberry jam
90 days
Raspberry jam
15 days  Peach
jam
90 days Peach
jam
Soluble solids ( °Brix)
Total dry matter (%)
44,97
40,17
45,86
41,5
42
41,92
44,1
42,9
35 40 45 50
15 days 
Raspberry jam
90 days
Raspberry j m
15 days  Peach
jam
90 days Peach
jam
Soluble solids ( °Brix)
Total dry matter (%)
Figure 1. The results obtained for total dry matter (%) 
and soluble solids (°Brix) in produced jams after storage 
of 15 and 90 days 
Results presented in Figure 1 shown that the total dry 
matter content of the jams increased during 90 days of 
storage, which reflected on the values for soluble sol-
ids. These results are in agreement with the results of 
Rehman et al. [3] who reported that total soluble solids 
increased from 66.5 to 68.8 in strawberry jam after 60 
days. In another study Ehsan et al. [7] reported a slight 
increase in total soluble solids of grape fruit apple mar-
malade from 70.0 to 70.8 after 60 days. The increase in 
total soluble solids contents of the product may be due 
to the solubilization of jam constituents during storage 
[8].
The ash value is a measure of the amount of added 
minerals. Natural ash content is due to the minerals 
like calcium, phosphorus and iron. Ash content of a 
foodstuff represents inorganic residue remaining after 
destruction of organic matter [5]. Time did not affect 
the ash content of the produced jams (Table 1). Similar 
observation was found by Clarissa et al. [9] who did not 
found change in ash content during the storage of a 
mixed araça and marolo jam. 
Journal of Hygienic Engineering and Design
27
Table 1. The effect of storage on ash, fats, vitamin C and 
proteins of produced jams 
Sample Raspberry jam Peach jam
Storage 
period
15 
days
90 
days
15 
days
90 
days
Ash (%) 0.29 0.29 0.22 0.22
Fats (%) 0.90 0.90 0.97 0.97
Vitamin C 
(mg/100 g) 19.40 19.40 15.20 15.20
Proteins (%) 1.76 0.48 1.82 0.27
Also, storage time did not affect on the content of the 
fats and vitamin C. According to Dauthy [10] about 30 
% of vitamin C found in the fresh fruit has been lost 
during the production of jam, but its remains in the 
finished product were stable during storage. Other 
authors reported decreassing of vitamin C during the 
storage of fruit products [4, 5, 8 and 11]. The ascorbic 
acid content decreased due to oxidation of ascorbic 
acid to dehydroascorbic acid [5], and the values of pro-
teins decreased also during storage.
The jam samples were analyzed for acidity after 90 
days of storage. In raspberry jam and peach jam, total 
acids increased from 1.47% to 1.49% and from 0.92% to 
0.97% respectively. There was a proportional decrease 
in pH value with the increased acidity during storage 
(Figure 2). The results are in complete agreement with 
other researchers [3, 4, 7, 8, 11 and 12]. The increase 
in acidity and decrease in pH may be ascribed to rise 
in the concentration of weakly ionized acid and their 
salts during storage [7 and 12]. This increase in acidi-
ty and decrease in pH might also be due to ascorbic 
acid degradation, hydrolysis of pectin or degradation 
of polysaccharides and oxidation of reducing sugar [4, 
7, and 11]. 
3,2
1,47 3 1,49 3,03
0,92
2,8
0,970
1
2
3
4
15 days 
Raspberry jam
90 days
Raspberry jam
15 days  Peach
jam
90 days Peach
jam
pH
Total acids (%)
Figure 2. The values obtained for total acids and pH in 
jams after storage of 15 and 90 days 
Sugars are the most important constituents of fruit 
product and are essential factor for the flavor of the 
food product and act as a natural food preservative 
[3]. From the results shown in Figure 3 it is evident that 
reducing sugar increased and non reducing sugar de-
creased in jam samples during the storage period. The 
increase in reducing sugars might be due to inversion 
of non-reducing sugars to reducing sugar (glucose + 
fructose) during storage [2, 3, 8 and 13]. 
Figure 3. The content of sucrose, glucose and fructose in 
jams after storage of 15 and 90 days
The results are in agreement with Muhammad et al. [8] 
who observed increasing trend in reducing sugars and 
decreasing trend in non-reducing sugars of diet apple 
jam during 3 months of storage. Ehsan et al. [7] while 
working on grape fruit apple marmalade observed in-
crease in reducing sugar and decrease in non-reducing 
sugar.
According to the values of the studied parameters, 
jams meet the conditions prescribed in the Regulation 
for special security requirements of fruit jams, jellies, 
marmalades and sweetened chestnut purée [14]. 
From the microbiological analysis in varieties of jams, 
it was estimated that the number of present micro-
organisms Listeria monocytogenes, Salmonella spp., 
Escherichia coli, yeast and must, that the number of 
present microorganisms were within the acceptable 
limits according to the regulation on microbiological 
criteria for foodstuffs [15] 
4. Conclussions
-  This work was aimed to producing low sugars jams 
from different fruits (raspberry, peach) and assess 
their quality characteristics during storage at ambi-
ent temperature.
-  Production of jams shown overall positive results 
although some changes occurred during storage in 
the levels of sucrose, protein, pH value, decreased, 
whereas the levels of total dry matter, soluble sol-
ids, reducing sugar and total acids, increased. The 
fats, vitamin C and ash content were not influenced 
by the time factor. The microbiological parame-
ters were within the standards established by the 
Macedonian legislation. Therefore, this jams stored 
for up to 3 months can still be consumed safely.
-  It was concluded that the products are of good 
quality both raspberry and peach fruit can be uti-
lized and preserved in the form of jam. So that the 
growers, processors and the consumers can get 
maximum benefits of theirs produce.
Journal of Hygienic Engineering and Design
28
5. References
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STORAGE IMPACT ON THE QUALITY OF RASPBERRY AND PEACH JAMS

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STORAGE IMPACT ON THE QUALITY OF RASPBERRY AND PEACH JAMS

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