Ảnh hưởng của các điều kiện chế biến và tác nhân tạo gel đến các đặc tính lý hóa học và cảm quan của mứt đông mít bổ sung vào sữa chua

J. Sci. & Devel., Vol. 12, No. 1: 78-88 
Tạp chí Khoa học và Phát triển 2014, tập 12, số 1: 78-88 
www.hua.edu.vn 
78 
EFFECT OF PROCESSING CONDITIONS AND GELLING AGENTS ON THE PHYSICO-CHEMICAL 
AND SENSORY CHARACTERISTICS OF JACKFRUIT JAM ADDING TO YOGURT 
Nguyễn Minh Thủy1*, Lý Nguyễn Bình1, Nguyễn Ái Thạch2, Nhan Minh Trí1, Hồ Thanh Hương1, 
Nguyễn Phú Cường1, Đinh Công Dinh2, Nguyễn Thị Mỹ Tuyền1 
1College of Agriculture and Applied Biology, Can Tho University, 2Master Student of Can Tho University 
Email*: nmthuy@ctu.edu.vn 
Received date: 21.10.2013 Accepted date: 16.01.2014 
ABSTRACT 
Jam is an effective and tasty way of preserving fruit. Most tropical fruits can be processed and preserved in 
order to reduce post harvest loss in small scale operations. The potential of the nutritious jackfruit (Artocarpus 
heterophyllus), has remained largely untapped. The study was conducted to investigate the effects of pectin 
concentration (0.7 to 0.9%) and gum arabic concentration (0.9 to 1.1%); vacuum pressure (450 to 650 mmHg) and 
holding time (2.5 to 4 minutes) on processing and jackfruit jam quality. Stirred and FOB-type fruit-flavored yogurt 
were made by adding jackfruit jam at different ratios (5 to 20%). In this work, vacuum technology was proven as 
adequate to obtain jam with the typical characteristics of water activity, degree Brix and viscosity of jam adding to 
yogurt. Proximate analysis showed vitamin C in jam 0.45 mg%, pH from 3.9 to 4 and oBrix from 53-54. The sensory 
evaluation showed that samples submitted to more intense vacuum pressure heating had signif icantly higher scores 
in color saturation, brightness, good texture and taste. These indicated that high vacuum pressure treatment prevents 
jackfruit jam color change and increases the consistency of the jam. In this way, jam was preferred by assessors 
mainly due to its higher consistency and suitability for adding to yogurt processing. The samples obtained by this 
procedure were stable during storage. Addition of 15% of Jackfruit jam into stirred yogurt and layered type of yogurt 
(FOB) provided products with strong aroma, good taste (sour and sweet harmony) and texture without water release. 
Keywords: Jackfruit, jam, thickening agent, yogurt, vacuum cooking. 
Ảnh hưởng của các điều kiện chế biến và tác nhân tạo gel 
đến các đặc tính lý hóa học và cảm quan của mứt đông mít bổ sung vào sữa chua 
TÓM TẮT 
Chế biến mứt đông là một trong các biện pháp bảo tồn chất lượng của trái cây. Hầu hết trái cây nhiệt đới có thể 
được chế biến và bảo quản nhằm giảm tổn thất sau thu hoạch với các hoạt động ở quy mô nhỏ. Tiềm năng của loại 
trái cây bổ dưỡng như mít (Artocarpus heterophyllus) vẫn chưa được khai thác triệt để. Nghiên cứu được tiến hành 
nhằm tìm hiểu ảnh hưởng của pectin (nồng độ 0,7-0,9%) và gum arabic (nồng độ 0,9-1,1%); áp suất chân không 
(450-650 mmHg) và thời gian giữ nhiệt (2,5-4 phút) đến tiến trình chế biến và chất lượng mứt đông. Sữa chua 
hương vị trái cây dạng khuấy và dạng lớp (FOB) được thực hiện bằng cách bổ sung mứt đông mít ở các tỷ lệ khác 
nhau (5-20%). Trong sản phẩm này, công nghệ chân không đã chứng minh ưu điểm vượt trội cho tiến trình chế biến 
để có được mứt đông mang các đặc tính lý hóa tốt về hoạt độ nước, độ Brix và độ nhớt phù hợp để bổ sung vào sữa 
chua. Phân tích sản phẩm cho thấy hàm lượng vitamin C của mứt khoảng 0,45 mg%, pH 3,9-4 và 53-54oBrix. Các 
đánh giá cảm quan thực hiện để so sánh các sản phẩm cho thấy mứt đông được chế biến ở điều kiện áp suất chân 
không cao cho giá trị cảm quan cao về màu sắc, độ sáng, cấu trúc và hương vị. Kết quả cũng cho thấy ứng dụng 
chân không trong công nghệ nấu mứt đã hạn chế sự biến đổi về màu sắc và tăng khả năng đồng nhất của sản 
phẩm. Đây cũng là đặc điểm được người tiêu dùng quan tâm và thỏa mãn các tính chất lý hóa của sản phẩm mứt 
đông bổ sung vào sữa chua trái cây. Sản phẩm đảm bảo an toàn và ổn định trong thời gian lưu trữ. Bổ sung 15% 
mứt đông mít vào sữa chua dạng khuấy và dạng lớp (FOB) đã cung cấp được các sản phẩm yaourt trái cây có 
hương thơm mạnh, vị hài hòa, cấu trúc tốt và hạn chế tình trạng tách nước trong sản phẩm theo thời gian tồn trữ. 
Từ khóa: Mít, mứt đông, nấu chân không, tác nhân tạo đông, sữa chua. 
Nguyễn Minh Thủy, Lý Nguyễn Bình, Nguyễn Ái Thạch, Nhan Minh Trí, 
Hồ Thanh Hương, Nguyễn Phú Cường, Đinh Công Dinh, Nguyễn Thị Mỹ Tuyền 
79 
1. INTRODUCTION 
Historically, jams were originated as an 
early effort to preserve fruit for consumption in 
the off-season (Baker et al., 2005). In 
traditional jam manufacture, all the ingredients 
are mixed in adequate proportions, and the mix 
is concentrated by applying a thermal 
treatment to reach the required final soluble 
solids content. Nevertheless, this process also 
implies an undesirable impact on color, 
nutritional value and flavor properties due to 
the high temperature in the cooking process. 
Vacuum cooking represents one of the most 
important technical innovations. It shows many 
nutritious, qualitative, hygienic and economic 
advantages. From a nutritional point of view, 
the low and constant cooking temperature 
allows for the minimization of changes in the 
vitamin content of jam. In addition, the process 
of cooking the jam inside a closed hermetic 
container avoids the loss of principal nutrients. 
The organoleptic characteristics of jam also 
benefit from vacuum cooking, the fruit’s natural 
tastes could be maintained after cooking. 
Fruit yogurts are very popular among milk 
products. Today, the consumer’s desire for a 
healthy and fresh diet that is also low in 
calories, thus, a wide range of fruit yogurts can 
be found. In the manufacturing of fruit yogurts, 
the fruit is usually added to the milk product in 
the form of fruit preparations (as jam). The 
addition of pectin or arabic gum as a thickening 
agent results in high-quality fruit preparations 
with exceedingly positive technological and 
sensory properties. Fruit yogurts are mainly 
distinguished by the way the fruit preparation 
and the yogurt are combined. The majority of 
yogurts are stirred yogurts where the fruit 
preparation is directly mixed with the stirred 
yogurt and then filled into the containers. 
Another large group are layered products. Fruit 
jam was prepared for this purpose. The 
formulation parameters such as content of 
soluble solids, pH as well as type and dosage of 
the thickening agents used have a significant 
effect on both the gelling properties and the 
texture of the fruit preparation. 
The aim of this work was to determine the 
type and dosage of thickening agents in Jackfruit 
jam processing. In addition, the vacuum 
conditions was monitored to obtain high quality 
jam and to manufature fruit yogurt. 
2. MATERIALS AND METHODS 
2.1. Materials 
Jackfruit pulp was collected from jackfruit 
variety of Thai origin cultivated in Vietnam. 
The jackfruit pulp collected was ground into 
small pieces. The ingredients used for jackfruit 
jam production included sucrose (CASUCO, 
Vietnam), thickeners (High-methoxyl pectin 
from apple, USA and Gum Arabic Powder - 
KB121, USA) and citric acid (China). Vacuum 
evaporation equipment (or jam evaporator) 
was used. 
2.2. Sample preparation 
- Jackfruit jam preparation 
Ten kilogram batches of jackfruit were 
prepared with 1: 1 Jackfruit pulp to tape water 
ratio. Next, the soluble solids were monitored 
during the process until the total soluble solids 
(TSS) reached 45o Brix. The pH value was 
controlled with a pH meter and adjusted in the 
range of 3.23.4 by citric acid. High methoxyl 
pectin (0.7; 0.8; 0.9 %w/w per total amount of 
jackfruit pulp, water and sugar) and gum arabic 
(0.9; 1.0; 1.1 %w/w per total amount of jackfruit 
pulp, water and sugar) were mixed with sugar 
and added into the vacuum chamber. The final 
mixture was boiled in vacuum pressure at 450, 
500, 550, 600 and 650 mmHg and holding time of 
2.5, 3.0, 3.5 and 4.0 minutes (with evaporated 
steam temperature of 54-66oC). The hot jam was 
then removed from the cooker and poured into 
sterile containers. Finally, jam were covered with 
lid tightly and cooled down to 37-39°C. 
- Yogurt preparation 
A solid non fat of fresh cow milk was 
standardized to 15% by milk powder (Vinamilk, 
Effect of processing conditions and gelling agents on the physico-chemical and sensory characteristics of jackfruit 
jam adding to yogurt 
80 
Vietnam). To improve the texture of yogurt, 
0.1% of gelatin (blom 220) was added to the 
milk at 40-45oC. The resulting mixture was 
homogenized at 65oC and 2500 psi and followed 
by heating to 80-85oC for 30 minutes. Then the 
mixture was rapidly cooled to 40-43oC. 
Incubation with starter culture (0.006 g/l) was 
performed in fermentation tank at 40-43oC for 
6-8 hours. The obtained yogurt (pH 4.6) was 
cooled to 20-25oC before mixing with jackfruit 
jam (5, 10, 15 and 20%) to produce stirred and 
FOB-type fruit-flavored yogurt. For making of 
FOB-type yogurt, the jam was laid on the 
bottom of the container which was further filled 
by yogurt. On the other hand, the jackfruit jam 
was directly mixed, stirred well with yogurt and 
then filled into the containers for making 
stirred yogurt. All experiments were performed 
in triplicate. 
2.3. Chemico-physical measurements 
The chemico-physical analysis of the 
Jackfruit jam was conducted in triplicates. 
Ascorbic acid content of the final products was 
analyzed by AOAC standard (2004). Total 
soluble solids (TSS-oBrix) and pH value was 
determined by using a refractometer (Model 
Atago Digital DBX-5) and digital pH meter 
(Model PHS-2F), respectively. The water 
activity of the samples was measured by Water 
Activity (aw value) Measurement Instruments 
(NOVASINA, Sweeden). The color of the jam 
treatments was determined using Minolta 
colorimeter (Model CR-200, N.J.); the apparatus 
was first calibrated using a white standard and 
then the L value was taken (L = lightness or 
darkness, 100 = white, 0 = black). The viscosity 
of Jackfruit jam was measured at room 
temperature by Brookfield Viscometer. 
2.4. Sensory evaluation 
Sensory analysis was done on the texture, 
color, flavor (taste), and smell of the Jackfruit 
jam and resultant fruity yogurt. The sensory 
evaluations were carried out by the panel of 10 
fixed panelists. 
For QDA analysis, each panel was 
requested to evaluate the fruit for various 
attributes using 5-point hedonic scale (0 = 
unacceptable, 1 = moderately unacceptable, 2 = 
neither good nor bad, 3 = moderately good, 4 = 
good) (Chapman et al., 2001). 
For logistic regression analysis (Menard, 
2002), the relationship between Logistic 
Regression and independent variable(s) could be 
described by the equation of the fitted model: 
Logistic Regression = exp()/(1+exp()), where  
= +1X + 2X2, = intercept and i = 
coefficients. Observed values for P (Y=1) must 
lie between 0 (unacceptable) and 1 (acceptable). 
2.5. Statistical analysis 
All statistical analyses were performed 
using Statgraphics Centurion Statistical 
Software (Version 15.2.11) for Microsoft 
Windows. The results were analyzed by ANOVA 
(Multiple Range Test) and the means were 
separated by LSD (P<0.05). The means and 
standard deviations were also calculated and 
plotted using Microsoft Excel software. 
3. RESULTS AND DISCUSSIONS 
The quality analysis of jackfruit is shown in 
Table 1. The TSSs in jackfruit were rather high 
(16.6oBrix) with the major component being 
sugar (15.84%). Jackfruit is also considered as a 
good source of antioxidant. 10.32 mg% of 
vitamin C content in the raw material was 
observed. 
Table 1. Quality criteria of jackfruit 
Quality criteria Content 
TSS (oBrix) 16.6±0.3* 
Sugar content (%) 15.84±0.25 
Acid content (%) 2.47±0.17 
pH 4.78±0.18 
Vitamin C content (mg%) 10.32±0.22 
Pectin content (%) 4.5±0.5 
Note: *Mean value standard deviation 
Nguyễn Minh Thủy, Lý Nguyễn Bình, Nguyễn Ái Thạch, Nhan Minh Trí, 
Hồ Thanh Hương, Nguyễn Phú Cường, Đinh Công Dinh, Nguyễn Thị Mỹ Tuyền 
81 
3.1. Effects of thickening agents on quality 
of Jackfruit jam 
3.1.1. Physico-chemical properties 
Traditional and major application of gelling 
agent in jam utilise gel forming activity of high 
methoxyl pectin (HMP) at low pH, high sugar 
concentration or low water activity. Dissolved 
sugar and acid conditions ensure that chain-
chain interactions dominate over chain-solvent 
interactions and high sugar condition creates 
low water activity which can be obtained by 
other solutes with the same resulting gels 
(Sharma, 2006). The effect of hydrocolloid 
concentration on the water activity, total 
soluble solid, pH value and viscosity of Jackfruit 
jam is shown in Table 2. 
The TSS of Jackfruit jam was 53 to 54ºBrix. 
Traditional jams carry up to 65ºBrix according 
to CODEX STAN 79-8 (CODEX STAN 79, 
1981). However, all jams formulated in this 
study carried 53oBrix, it can be labeled as 
reduced-calorie jams. 
There was no significant difference (P<0.05) 
in water activity between the jams which were 
cooked with different combined concentrations 
of HMP and gum arabic. Water activity (aw) 
determines the lower limit of available water for 
microbial growth (Decagon Devices Inc, 2007). 
In general, the minimum aw for most moulds 
was 0.8, most yeasts 0.85, osmophilic yeasts 
0.6-0.7 and most bacteria 0.9. pH of the jams 
remained constant at 3.9-4.0. 
The results also demonstrated that an 
increase in HMP concentration had a significant 
effect (P < 0.05) on the viscosity of Jackfruit 
jam. Because pectin was used to control 
viscosity or characteristics the gel-like solution 
associated with fruits (Caballero et al., 2003) 
and high molecular weight pectin tend to 
increase jam viscosity and these values depend 
upon pectin concentration (Imeson, 2010). 
According to McWilliams (1997), the role of 
hydromethoxyl pectin is to form a network or 
create a thickening effect for jam. Hence, the 
more pectin used, the thicker the jam. However, 
high viscosity jam is not suitable for adding to 
yogurt. Therefore, a combination of HMP and 
gum arabic was necessary to add into Jackfruit 
jam. The aim of this work was to reduce the 
stickiness and the combination of HMP and 
gum arabic is often used for desirable texture of 
yogurt. Gum arabic exhibits very low viscosity 
in water, it has a high branched compact 
arabinogalactan structure which gives a low 
viscosity solution together with a central 
protein fraction that provides good 
emulsification properties (Thevenet, 2010). 
3.1.2. Sensory evaluation 
Results from QDA were informative for 
statistical analysis, and means of attributes in 
the same sensory category are graphically 
presented in Figure 1. There was a significant 
difference in all sensory attributes (color, odor, 
flavor and texture) among products. The 
stickiness decreased with the addition of gum 
arabic to gel formulation without water release. 
In general, the use of HMP (0.8%) and gum 
 ... calorie 
jam type. Fruit products, such as jams and jellies, 
are heated for long period during preparation. 
This not only destroys vegetative microorganisms, 
but also reduces aw by partial inversion of the 
sucrose present (Lund et al., 2000). 
Table 3. Effect of vacuum pressure and holding time 
on water activity (aw) of Jackfruit jam 
Holding time (minutes) 
Vacuum pressure (mmHg) 
Average 
450 500 550 600 650 
2.5 0.929 0.927 0.931 0.930 0.935 0.930c 
3 0.925 0.925 0.929 0.933 0.93 0.928b 
3.5 0.927 0.924 0.925 0.925 0.930 0.926b 
4 0.907 0.923 0.925 0.927 0.926 0.921a 
Average 0.922a 0.925b 0.928c 0.929cd 0.930d 0.927 
Note: Significant differences were indicated by different letters in the same row or column 
Nguyễn Minh Thủy, Lý Nguyễn Bình, Nguyễn Ái Thạch, Nhan Minh Trí, 
Hồ Thanh Hương, Nguyễn Phú Cường, Đinh Công Dinh, Nguyễn Thị Mỹ Tuyền 
83 
Viscosity 
The viscosity of the products was high in 
low pressure vacuum condition or long holding 
time (Figure 2). The highest value was obtained 
at 22,000 cP when applying vacuum pressure of 
450 mmHg and holding time of 4 min for jam 
processing. It was observed that high 
evaporation temperature and long cooking time 
of jam resulted in increasing evaporation 
intensity and viscosity. And then, the viscosity 
decreased to the lowest level, nearly 10,000 cP 
as cooking condition at 650mmHg and 2.5 min 
was applied. At the same holding time, it seems 
not significantly different between the viscosity 
of samples which were cooked at higher vacuum 
pressures (from 500 to 650 mmHg). 
Color (L value) 
Vacuum evaporation, since it happens in a 
medium depleted of oxygen and at lower 
temperature, preserved color, flavor and 
vitamins (Sinha et al., 2012). In addition, it also 
limited caramelization that gave the final 
products with caramel flavor and brown color. 
Table 4 shows the vacuum pressure increase 
from 450 to 650 mmHg at the same holding 
time (2.5 min), a brighter color of products was 
observed (or L value increases). Besides, L value 
decreased slightly in holding time between 2.5 
and 4 minutes at the same vacuum pressure 
level (650 mmHg). The optimum cooking 
conditions for Jackfruit jam may be at vacuum 
pressure of 650 mmHg during 3 minutes due to 
high score of sensory value obtained. Therefore, 
coloring is not required for jams produced from 
fresh fruit, when the boiling time is short and 
the heat is not excessive (Hui et al., 2006). 
Ascorbic acid content 
The main objective of the vacuum 
evaporation system is to reduce the boiling 
point of the liquid to be evaporated, thus 
reducing the heat requirement in both the 
boiling and condensation processes. Besides, 
another technical advantage is the limitation of 
the decomposition of substances that are 
sensitive to temperature, such as vitamin C, 
thiamine... Among water-soluble vitamins, 
vitamin C is one of the most important 
substances in evaporation or concentration 
operation. Therefore, this process must be 
performed in as short time as possible and at 
the lowest temperature in order to save heat 
sensitive substances (Watzl, 2003). 
Ascorbic acid is generally considered as a 
important nutritional quality indicator in food 
processing. The obtained data indicated that 
ascorbic acid content reduced when the products 
were heated at low pressure vacuum (or high 
evaporation temperature) or long holding time. 
The highest content of ascorbic acid was 
observed in jam was boiled at 650 mmHg and 
the duration of 2.5 to 3 minutes (Figure 3). The 
degree of ascorbic acid lost is closely related to 
the oxidation-reduction conditions and the 
residual enzyme activity (Bayindirli, 2010). 
0
5000
10000
15000
20000
25000
450 500 550 600 650
Vacuum Pressure (mmHg)
V
isc
os
ity
 (c
P)
2.5 min 3 min 3.5 min 4 min 
Figure 2. Effect of vacuum pressure and holding time on viscosity of Jackfruit jam 
Note: Error bars indicate the standard deviation of the mean values 
Effect of processing conditions and gelling agents on the physico-chemical and sensory characteristics of jackfruit 
jam adding to yogurt 
84 
Table 4. Effect of vacuum pressure and holding time 
on the color (L value) of Jackfruit jam 
Holding time (minutes) 
Vacuum pressure (mmHg) 
450 500 550 600 650 
2.5 61.53±0.22 61.09±0.71 62.85±0.03 63.66±0.28 64.78±0.87 
3 61.34±0.62 61.68±0.30 61.78±0.05 62.88±0.62 64.84±0.56 
3.5 61.66±0.30 61.00±0.52 61.34±0.43 62.41±0.55 63.58±0.37 
4 60.44±0.28 60.59±0.13 61.15±0.85 61.04±0.69 61.86±0.67 
Note: *Mean value standard deviation 
0.0
0.1
0.2
0.3
0.4
0.5
0.6
450 500 550 600 650
Vacuum pressure (mmHg)
A
sc
or
bi
c 
ac
id
 (m
g%
) 
2.5 min 3 min 3.5 min 4 min 
Figure 3. Effect of vacuum pressure and holding time 
on ascorbic acid content of Jackfruit jam 
Note: Error bars indicate the standard deviation of the mean values 
3.2.2. Sensory evaluation 
Jam cooked in vacuum evaporator limited the 
loss of fruit aromas and retained fruity characters 
because the fragrant substances are lost to the 
condenser water in vacuum pan, instead of to the 
atmosphere (Phillips et al., 1952). 
The sensory attributes (color, odor, flavor 
and texture) of Jackfruit jam cooked in different 
vacuum pressure levels (450÷650 mmHg) were 
evaluated by a panel of trainees. There was no 
significant difference in the texture among the 
products (Figure 4). However, in general, the 
higher score of sensory evaluation (in terms of 
color, odor and flavor) of finished product was 
associated with increasing vacuum pressure 
levels from 450 to 650 mmHg (in the same 
holding time of 3 minutes) for jam processing. 
This can be explained by the negative effects of 
high temperature (low vacuum pressure) on 
fruity flavor, color and aroma changes. In 
addition, cooking in lower vacuum pressure (or 
higher temperature) could promote browning 
reactions in Jackfruit jam. 
Nguyễn Minh Thủy, Lý Nguyễn Bình, Nguyễn Ái Thạch, Nhan Minh Trí, 
Hồ Thanh Hương, Nguyễn Phú Cường, Đinh Công Dinh, Nguyễn Thị Mỹ Tuyền 
85 
0
1
2
3
4
Color
Odor
Flavor
Texture
450 mmHg
500 mmHg
550 mmHg
600 mmHg
650 mmHg
Figure 4. Radar graph showing the sensory profile of the Jackfruit jam samples cooked 
with different vacuum pressure levels (holding time of 3 minutes) 
3.3. Effect of percentage of Jackfruit jam 
on the sensory characteristics of fruit 
yogurt (stirred or layered yogurt types) 
Stirred yogurt 
The yogurt mixed with jackfruit jam (5-20%) 
had different organoleptic value. After blending 
yogurt with jam (the concentrations of 5, 10, 15 
and 20%), the sensory characteristics (syneresis, 
smoothness, sweetness, acidity, flavor and color) 
of the fruit were evaluated (Figure 5). By 
increasing fruit jam from 5 to 20%, the sweetness 
of yogurt was observed. Adding lower jam (<5%) 
in yogurt, the natural flavor of fruit in yogurt was 
less recognized. In contrast, the yogurt was more 
difficult to make and required longer time of 
stirring when higher amount (>15%) of jam 
added to in yogurt 
The acceptability of consumers for fruit 
yogurt prepared with different percentage of 
Jackfruit jam was also analysed using Logistic 
regression model (Figure 6). With the obtained 
data from the panelists, the Logistic Regression 
was estimated using non-linear regression 
analysis by 2 parts of equation: 
0
1
2
3
4
Fruity flavor
Fruity color
Sweetness
Sourness
Smoothness
Syneresis
5% 10%
15% 20% 
Figure 5. Radar graph showing the sensory profile of the Jackfruit yogurt samples 
prepared with different percentage of Jackfruit jam 
Effect of processing conditions and gelling agents on the physico-chemical and sensory characteristics of jackfruit 
jam adding to yogurt 
86 
For the first part of equation (observed 
values for 5 to 15% of Jackfruit jam adding to 
yogurt), the output shows the results of fitting a 
logistic regression model to describe the 
relationship between Logistic Regression (1) 
and 1 independent variable. The equation of the 
fitted model is: 
Logistic Regression (1) = exp(1)/(1+exp(1)) (1) 
where 1 = 1.899 – 1.125X + 0.079X2 (X: 
percentage of Jackfruit jam) 
For the second part of equation (observed 
values for 10 to 20% of Jackfruit jam adding to 
yogurt), the output shows the results of fitting a 
logistic regression model to describe the 
relationship between Logistic Regression (2) 
and 1 independent variable with the equation of 
this fitted model as: 
Logistic Regression (2) = exp(2)/(1+exp(2)) (2) 
where 2 = -29.331 + 4.08X – 0.128X2 (X: 
percentage of Jackfruit jam). 
The P-value for these models (equa. 1 and 
2) in the Analysis of Deviance tables are less 
than 0.05, indicating that there is a 
statistically significant relationship between 
the variables at the 95% confidence level. The 
results showed the highest acceptability of 
consumers for fruit yogurt with 15 to 17% 
Jackfruit jam added into yogurt. Thus, mixing 
15% of jam into yogurt seemed to be a good and 
economical choice. 
FOB yogurt 
SY: Stirred yogurt; FOB: Fruit on bottom 
This study also investigated layered yogurt 
or FOB yogurt style to reduce water separation 
and to limit the structural breakdown of 
product. FOB yogurt type contained the jam on 
the bottom of the cup, followed by the top layer 
of fermented yogurt. Before consumption it 
requires blending to mix the fruit preparation 
(Chandan, 2006). The results indicated that the 
additional methods and percentage of jam affect 
sensory values of the finished product (Table 5). 
The percentages of added jam from 10 to 
20% provided FOB yogurt with high 
acceptance scores. However, 15 to 20% of 
added Jackfruit jam gave products more 
attractive, but there was no significant 
difference (p<0.005) based on the sensory 
evaluation among these samples. Layered 
yogurt, by comparison, was of much higher 
overall acceptable score because the natural 
structure of yogurt was broken by blending. 
The final products, including stirred yogurt 
and FOB yogurt, were shown in Figure 7.
5 7 9 11 13 15
0
0,2
0,4
0,6
0,8
1
Lo
gi
st
ic
 R
eg
re
ss
io
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16 18 20
Percentage of Jackfruit jam
14
Percentage of Jackfruit Jam
Lo
gi
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 R
eg
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io
n
Plot of Fitted Model; 
with 95,0% confidence limits 
Figure 6. Consumer acceptability of stirred yogurt prepared 
with different percentage of Jackfruit jam 
Note: The blue line (middle) is the mean of observatory values, the red line (above and below the mean) is deviation of the 
mean was evaluated from the panelists 
Nguyễn Minh Thủy, Lý Nguyễn Bình, Nguyễn Ái Thạch, Nhan Minh Trí, 
Hồ Thanh Hương, Nguyễn Phú Cường, Đinh Công Dinh, Nguyễn Thị Mỹ Tuyền 
87 
Table 5. Effect of additional methods and percentage of jam on overall 
acceptability of 2 types of yogurt (based on hedonic scale 0 to 9) 
The additional method - Percentage of jam Overall acceptability 
SY – 5% 5.9ab 
SY – 10% 7.6c 
SY – 15% 6.9bc 
SY – 20% 5.5ab 
FOB – 5% 5.3a 
FOB – 10% 7.5c 
FOB – 15% 8.1c 
FOB – 20% 8.3c 
Note: Significant differences were indicated by different letters in the same row or column 
a. Fruit on bottom (FOB) yogurt b. Stirred yogurt 
Figure 7. Jackfruit yogurt 
4. CONCLUSION 
Vacuum technique improved Jackfruit jam 
texture and color and it might be considered as 
a new technique for producing high quality fruit 
containing products. Fruit jam additions have 
developed fruit marketing an increasing effect 
on yoghurt consumption. Fruit yogurt was rated 
with higher acceptances by panelists because of 
coordination between jackfruit flavor and dairy 
products. The evidence from this study 
suggested that fruit additives to yogurt 
increased acceptability of yoghurt. 
ACKNOWLEDGEMENT 
The authors would like to thank the RIP 
Project for the financial support given throughout 
the Project ZEIN2011RIP13 (2011 – 083). 
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