Raw milk is heat treated in different ways to improve the safety of the milk for consumption. The heat treatment imparts different sensory properties to the milk that may influence its acceptance by consumers. In Ghana, fresh milk is boiled and sold locally to consumers. Generally, consumption amongst women of reproductive age and children under five is low. In this study, the sensory properties that drive liking for local boiled milk and other heat-treated milks in women of reproductive age and children between 1 and 5 years of age was studied. External preference mapping was used to understand the sensory properties of the milks that were liked by the two consumer groups. The sensory properties of boiled milk that made women of reproductive age like a particular product was its sweet and salty taste, smooth mouthfeel and artificial flavour. For children between 1 and 5 years, the oily aftertaste, boiled egg aroma as well as its sweet taste made them like the same product as the adults. This product also had a cooked aroma and flavour which could have influenced liking in the consumer groups. A small minority of adult consumers liked products that had a smooth and runny appearance with a raw/uncooked note.
Ghana is a developing country facing malnutritional challenges amongst children and women of reproductive age [1-3]. The first thousand days of life can positively or negatively impact the long term health of an individual [4-6]. This means that the nutritional status of an adult woman is directly associated with nutritional intake at birth. It is therefore necessary to provide the needed nutrients for optimal growth of children at an early age so as to produce healthy adults.
Milk is an important food commodity when it comes to the provision of nutrients for growth and development. It contains high amounts of calcium for maximal bone mineralization; omega-3 fats which help prevent the onset of cardiovascular diseases; vitamins B, E, selenium and zinc which help in the regulation of blood sugar and the removal of free radicals from the body and also contain complete proteins to promote normal growth and development [7].
Despite the many health benefits of milk, milk consumption in developing countries like Ghana is relatively low compared with other developed countries. Although consumption of dairy products is on the rise in many urban communities in Ghana, generally, fresh milk consumption is very low. There are some communities in Ghana where dairy activities may influence milk consumption patterns of consumers who live in these areas. Dairy communities in this context are defined as communities where dairying activities such as farming, processing and marketing occur. In Ghana, there are pockets of such areas typically in peri-urban communities.The demand for milk in these communities and most developing countries as a whole is expected to increase due to drivers like increasing income levels, urbanization, social and cultural factors.
Raw milk is often subjected to heat treatment to make it safe for consumption. The heat treatment imparts different sensory properties in the milk which may influence the acceptance of the milk for consumption. Cardello describes in vivid detail how this food-related phenomon leads to a measurable psychophysical behaviour [8]. In many dairying communities, raw milk is often boiled and sold locally as boiled milk. These heat-treated milks may have uncharacteristic sensory properties that make them different to industry processed heat-treated milks, which often have no off-flavour and are bland in flavour. Products such as the Ultra-High Temperature (UHT) treated milk, have characteristic cooked notes but are ‘clean’ with no other off flavours, they may have sweet or bitter taste [9]. In Ghana, these UHT milks are sold as fresh milk and are perceived to have improved hygiene due to its neat packaging. Local boiled milks are not packaged and are sold directly to consumers from the fire (with ice blocks to cool down the temperature) in milk markets or sold at farm gates as fresh pasteurised milk. There is thus a general perception that they are unsafe for consumption since milk is a fertile food for contamination with microorganisms [10]. Aside the safety issues, there may be some sensory barriers to the consumption of boiled milk amongst consumers in Ghana due to the uncharacteristic flavour notes that are typical in local boiled milks.
To promote the dairy market in Ghana, it is important to understande the sensory attributes that drive the acceptance and consumption of boiled milk amongst target consumers. A useful tool that can help to unearth the sensory properties of a product that drive liking in consumers is preference mapping. This method combines analytical data from descriptive work and consumer work to help understand what attributes in food are driving consumers to like or dislike food [11-13]. There are two basic approaches to preference mapping: Internal and external preference mapping methods. Both approaches have specific applications. Internal preference mapping focuses on the preference of consumers whiles external preference mapping focuses on understanding sensory information about the product and overlaying this information with consumer liking data [11]. In this study our main objective was to use external preference mapping tool to understand the sensory drivers for consumption of boiled milk in children under 5 years old and women of reproductive age (15-49 years). These consumer target groups are identified as nutritionally vulnerable groups in our society. Enhanced milk consumption amongst this target group would be ideal as the one single source food can provide the needed nutrients in two nutritionally vulnerable groups in society.
A total of 35 sensory attributes were used to characterise the sensory profile of the 8 different milks based on the appearance (7 attributes), aroma (7 attributes), flavour (12 attributes), mouthfeel (2 attributes) and aftereffects (7 attributes). There were statistical significant differences between the samples for all attributes evaluated with the exception of mouthfeel descriptors, smooth and runny. All other sensory descriptors generated were significantly discriminating between the boiled milk samples (Table 1 and 2). Table 3 shows the sensory descriptive attributes for the products and the food reference material that relate to those attributes on a 15cm intensity line scale.
|
Products |
|||||||
Sensory Descriptors |
A |
B |
C |
D |
E |
F |
G |
H |
Appearance |
||||||||
Smooth |
148.34a |
148.53a |
145.13a |
146.08a |
146.67a |
149.60a |
148.70a |
133.59b |
Runny |
142.33a |
142.09ab |
141.66ab |
142.30ab |
142.19ab |
141.32ab |
142.28ab |
141.30b |
Glossy |
125.40bcd |
129.03abc |
120.04d |
131.09ab |
121.90cd |
137.50a |
129.40abc |
117.75d |
Opaque |
148.04bc |
148.42b |
148.39 |
147.08d |
148.39b |
149.53a |
148.07bc |
147.45a |
Cream |
48.10bc |
46.44c |
60.44bc |
52.47bc |
47.86bc |
61.66b |
99.02a |
53.96bc |
Fat droplets |
24.92b |
14.25c |
21.36bc |
15.49c |
20.86bc |
2.33d |
2.02d |
34.79a |
Particles at the bottom |
10.57ab |
6.71bc |
11.44a |
1.78d |
3.77cd |
0.23d |
0.20d |
0.99d |
Mouthfeel |
||||||||
Smooth |
148.27 |
142.61 |
145.19 |
148.10 |
148.05 |
144.23 |
148.56 |
148.35 |
Runny |
142.29 |
142.17 |
141.84 |
142.25 |
142.36 |
142.09 |
141.95 |
142.18 |
Aftertaste |
||||||||
Sweet |
6.71b |
2.32b |
6.99b |
5.91b |
4.03b |
8.00b |
3.09b |
46.09a |
Salty |
5.26a |
1.28b |
2.05b |
2.71b |
1.74b |
1.69b |
2.10b |
2.57b |
Salivation |
22.68a |
25.0a |
24.53a |
28.71a |
20.39a |
27.48a |
19.73a |
24.74a |
Oily |
15.67b |
10.19bcd |
11.54bc |
13.05bc |
14.38b |
6.91cd |
4.33d |
28.32a |
Milky |
23.27cd |
12.28e |
29.39bc |
25.96a |
24.26a |
46.91a |
17.24de |
33.64b |
Astringent |
18.96ab |
15.65b |
20.68ab |
16.87ab |
25.31a |
21.09ab |
17.90ab |
22.99ab |
Fresh cow meat |
16.43b |
31.65a |
17.10b |
31.46c |
33.77a |
3.07c |
10.40bc |
4.81c |
|
Products |
|||||||
Sensory Descriptors |
A |
B |
C |
D |
E |
F |
G |
H |
Aroma |
||||||||
Milky |
73.55c |
75.68c |
75.16c |
64.45cd |
60.42d |
138.64a |
128.13a |
102.23b |
Cooked note |
58.54c |
56.78c |
57.44c |
53.84c |
55.68c |
93.32a |
80.34b |
79.62b |
Artificial flavour |
7.50bc |
0.28c |
0.44c |
0.34c |
0.43c |
8.91b |
2.13bc |
75.46a |
Cereal |
5.84bc |
23.12a |
10.28b |
9.56b |
9.50b |
7.33b |
0.28c |
6.32bc |
Cowy/Meaty |
28.65cd |
45.64b |
29.78c |
59.90a |
57.76ab |
5.06e |
17.19de |
8.11e |
Raw/Uncooked |
22.62cd |
67.20a |
15.78de |
42.72b |
41.40b |
7.32e |
32.73bc |
9.68de |
Smoky |
6.97cd |
18.03b |
63.41a |
5.85cd |
16.70bc |
2.43d |
0.35d |
7.73bcd |
Flavour |
||||||||
Sweet |
14.47b |
9.66b |
12.64b |
13.77b |
9.18b |
12.16b |
9.09b |
87.88a |
Salty |
8.35a |
4.99b |
5.30b |
5.04b |
3.65b |
4.36b |
3.55b |
5.93ab |
Milky 1 |
36.99b |
10.12cd |
20.72c |
9.38cd |
12.52cd |
9.39cd |
6.09d |
78.55a |
Milky 2 |
63.59b |
65.09b |
65.08b |
86.72a |
88.81a |
4.73c |
6.29c |
9.64c |
Milky 3 |
14.84e |
31.74cd |
38.50c |
16.50de |
16.23de |
127.67a |
104.08b |
23.31cde |
Cowy/Meaty |
40.48b |
56.53a |
38.74b |
59.17a |
66.46a |
4.13d |
16.89c |
8.79cd |
Raw cow meat |
30.91c |
51.09b |
31.36c |
48.68b |
60.96a |
6.33d |
22.12c |
5.09d |
Artificial Flavour |
5.89b |
0.37b |
0.36b |
0.38b |
0.20b |
4.63b |
0.41b |
79.58a |
Eggy 1 |
5.02ab |
7.09ab |
7.38ab |
10.30a |
9.90a |
1.94b |
6.49ab |
11.20a |
Eggy 2 |
10.98bc |
2.15c |
2.11c |
2.22c |
6.59bc |
17.32b |
35.09a |
11.39bc |
Cereal |
12.17b |
22.63a |
9.44bc |
10.48b |
9.53bc |
6.57bc |
0.27c |
8.54bc |
Table 2: Mean scores of boiled milk products based on sensory descriptors (modalities-aroma and flavour).
Appearance |
|||
Descriptor |
Definition |
Anchor |
Scale/ |
Smooth |
Absence of lumps in UHT milk |
Not to very |
7-lumps |
Cream colour |
Characteristic cream colour associated with laughing cow cheese |
Not to very |
2-UHT milk |
Runny |
Ability to flow easily like water |
Not to very |
1-ketchup |
Opaque |
Inability to see through |
Not to very |
15-UHT milk |
Glossy |
Having a shiny surface associated with UHT milk |
Dull to glossy |
7-laughing cow cheese |
Fatty droplets |
Fat particles on the surface of milk |
Not to very |
0-absent |
Particles at the bottom of milk sample |
Presence of black particles at the bottom of milk sample |
Not to very |
0-absent |
Aroma |
|||
Descriptor |
Definition |
Anchor |
Scale/ Reference |
Milky |
Characteristic aroma of milk |
Not to very |
5-fresh milk |
Meaty/Cowy |
Characteristic aroma of fresh cow meat |
Not to very |
|
Cooked note |
Aroma of milk |
Not to very |
5-UHT milk |
Artificial flavour/Essence |
Aroma of vanilla and caramel sweet essence |
Not to very |
|
Raw/Uncooked |
Pungent aroma associated with raw meat and raw egg |
Not to very |
5-partially scrambled |
Smoky |
Aroma of uncooked turkey bacon |
Not to very |
6-smoked mackerel |
Cereal |
Aroma associated with processed maize product |
Not to very |
|
Flavour |
|||
Descriptor |
Definition |
Anchor |
Scale/ Reference |
Sweet |
Basic sweet taste |
Not to very |
|
Meaty/Cowy |
Flavour of fresh cow meat |
Not to very |
|
Smoky |
Aroma of uncooked turkey bacon |
Not to very |
6-smoked mackerel |
Salty |
Basic salt taste |
Not to very |
|
Milky 1 |
Flavour of powdered milk |
Not to very |
Milky 1: 10-powdered milk |
Cooked note |
Flavour of boiled milk |
Not to very |
5-UHT milk |
Raw/Uncooked |
Pungent flavour of raw meat, raw egg |
Not to very |
5-partially scrambled |
Cereal |
Reminiscent flavour of boiled maize |
Not to very |
|
Eggy 1 |
Reminiscent flavour of boiled egg |
Not to very |
Eggy 1: 6-boiled egg |
Mouthfeel |
|||
Descriptor |
Definition |
Anchor |
|
Smooth |
Absence of lumps |
Not to very |
|
Runny |
Ability to flow easily in the mouth |
Not to very |
|
Aftertaste |
|||
Descriptor |
Definition |
Anchor |
|
Salivation |
Production of saliva in the mouth |
Not to very |
|
Fresh cow meat |
Lingering cowy note in the mouth |
Not to very |
|
Oily |
Oily coating in the mouth |
Not to very |
|
Sweet |
Basic sweet taste |
Not to very |
|
Milky |
Lingering milk taste in the mouth |
Not to very |
|
Astringent |
Dryness in the mouth |
Not to very |
|
Salty |
Basic salt taste |
Not to very |
Table 3: Sensory attributes of boiled milk products and their associated food reference materials on the intensity scale.
Fresh milk consumption in Ghana is generally very low and particularly so amongst children and women of reproductive age. This study has provided insight into the sensory drivers that influence consumption of different types of boiled milk products on the local Ghanaian market. Significantly, attributes associated with products that were UHT treated (products F and G) in this study, did not drive liking amongst either consumer groups. Both adult women of reproductive age and children under five years liked the sample H although the attributes that drive liking for the two groups were different. For women of reproductive age, sweet and salty taste, artificial aroma and flavour and smooth mouth feel are important attributes for product liking while for children under five years, oily aftertaste, eggy 1 (boiled egg flavour) and oily droplets in appearance were important attributes that drive liking. For a small majority of adult women of reproductive age however, products that have a raw/uncooked aroma and smooth runny appearance were more desirable. A small majority of children consumers however were non-discriminating between the products and liked all the products about the same. The results of this study show that there is potential to develop the local fresh milk market in the Ghana as they have sensory properties that appeal to the target consumers used in this groups who are also a nutritionally vulnerable group in the population.
The study was funded by the Bill and Melinda Gates Foundation. The funder did not influence in any way, the design of the study, collection, analysis and interpretation of data. The study was also funded with UK aid from the UK government; however, the views expressed do not necessarily reflect the UK government’s official policies.
Citation: Adjei MYB, Amissah JGN, Parry-Hanson Kunadu A, Acquaah E, Colecraft, E et al (2018) Drivers-of-Liking (DOL) for Boiled Milk among Women of Reproductive Age and Children Aged between One and Five Years in Peri-Urban Communities in Ghana. J Food Sci Nut 4: 034.
Copyright: © 2018 Maame Yaakwaah Blay Adjei, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.