Analysis of consumers’ preference on taro-flavored UHT Ultra milk using conjoint method in Malang City

UHT One of the processed milk products is Ultra Taro UHT milk. The aim of this research was to analyze Ultra Taro UHT milk’s importance level of attributes and combinations of the attributes which are preferred based on consumer preferences. This study was quantitative correlational using a questionnaire with a full profile presentation method. The study was conducted for one month, with 60 respondents determined by the purposive sampling method. Data was processed using the conjoint method. In this research, 4 product attributes were used, there are flavor with 3 levels, volume with 3 levels, fat content with 2 levels, and type of packaging with 2 levels. The results showed the level of importance value, attribute flavor with a relative value of 34.44%, volume and packaging types have similar relative value of 27.79%, and fat content with a relative value of 9.97%. The combination of attributes favored by consumers was the fifth stimuli with a total use value of 3.8283 consisting of taro balanced milk flavor attributes, 200 ml volume contents, low fat, and tetra pack packaging types. The results of the conjoint have significant correlation with the opinion of respondents with a positive Kendall Tau correlation value of 0.889.


Introduction
According to the data of the Central Statistics Agency of Indonesia (BPS, 2020), fresh milk is one of the food commodities with production levels reaching approximately 909,638 tonnes in 2018. The high production level of fresh milk in Indonesia has resulted in various processed products manufactured. Ultra-High Treatment (UHT) is one of the processed products of fresh milk.
UHT milk product was made by heating milk at a temperature of 138 -150 O C for 2 seconds. UHT processing of milk destroys all of the microorganisms capable of growing under the normal conditions of product storage. Under these conditions (i.e. very high temperature for a short time), the chemical, physical and organoleptic changes are kept to a minimum (Datta et al., 2002). There are several reputable companies producing UHT milk; one of them is PT. Ultrajaya Milk Industry, a company engaged in the consumer goods industry. PT. Ultrajaya Milk Industry has produced various products, namely Ultra milk full cream, Ultra milk low fat hi-calcium, Ultra mimi and Ultra milk, which comes in several flavor variants such as mocha, strawberry, and chocolate. Also, their latest flavor variants launched in 2018, caramel and taro.
Taro-flavored UHT Ultra milk is one of the innovations developed by PT. Ultrajaya Milk Industry. High consumption of milk products in Indonesia, particularly in Indonesia, has brought a significant number of manufacturers to produce processed milk products, especially UHT milk. This condition requires PT. Ultrajaya Milk Industry to create certain innovations for its product to compete in the market successfully. Manufacturers are demanded to be more consumers' preference oriented to develop a product following the consumers' needs.
Consumers' preference is one likes or dislikes toward certain goods or services. Consumers' preference shows consumers' likeness based on the existing product choices (Utami, 2011). In this research, the consumers' preference is obtained through the conjoint method. According to Suyanto and Darmawan (2020), conjoint analysis is based on the value combination assessment of each March 1975. This company is located in Jalan Raya Cimareme 131, Padalarang, West Java, and has distributed its products to various regions abroad and domestically. One of the areas is Malang, with its domestic market target as many as 90% and the export market target as many as 10%. Fresh milk ingredients used for producing UHT Ultra milk were obtained from cow's milk from dairy farming of PT. Ultrajaya Milk Industry in Pangalengan, Jawa Barat.

Respondent's Demographic and Characteristics
For around one month of the research process, 60 respondents met the required criteria. Based on their age, 55 respondents were 17-25 years old, three respondents were 25-30 years old and two respondents were 30-40 years old. Teenagers dominate the consumers of taro-flavored UHT Ultra milk. Based on gender, there were 48 female respondents and 12 male respondents. In Malang, taro-flavored UHT Ultra milk was consumed more by female respondents than male respondents. Furthermore, 53 respondents were students/college students, four respondents were employees, one respondent was a private-sector worker, one respondent was a consultant and one respondent was co-assistant. The consumers of taro-flavored UHT Ultra milk in Malang were mostly students or college students. This might happen as in Malang, there are a lot of universities and the students need to consume high protein products to keep their balanced diet. Forty-five respondents were high school graduates, and 15 respondents were college graduates. Most respondents were high school graduates, as they still went to college. Based on the questionnaire <IDR,500,000, 23 respondents had monthly income of IDR1,500,000 -IDR3,000,000 and 4 respondents had monthly income of >IDR3,000,000. Respondents who had a monthly income of <IDR1,000,000 -IDR1,500,000 were able to buy taro-flavored UHT Ultra milk at least twice in the last one month.

Validity Test
Validity test used Pearson's R correlation since the questionnaire applied the scoring scale. According to Kimberlin and Winterstein (2009), a validity test is performed to gauge the accuracy of the measurement instrument. A questionnaire can be considered as valid if it is able to solve the measured problems. The results of the test are shown in Table 1. The significance of all attribute levels examined was <0.05, indicating that the data was valid or was considered successfully solving the existing problems. According to Taber (2018), a variable is considered as valid if its score correlates significantly with its total score.

Reliability Test
In this research, the reliability test used Cronbach's Alfa technique with SPSS 17.0 software. According to Cho et al. (2015), reliability testing with Cronbach's Alfa technique is performed for interval/essay data type. According to Ursachi et al. (2015), reliability means how trusted a measurement result is. The results of the reliability test are shown in Table 2.
Cronbach's alpha value is 0.606. Based on the criteria of reliability test, this value is included in high criteria so that the data obtained is trusted. According to Prasetyawati and Ramli (2012), the result of the reliability test is considered reliable if Cronbach's alpha value of x and y variable is positive and above 0.6.

Consumer Preference Against Taro-Flavored UHT Ultra milk
Consumers' preference is consumers' assessment of a product based on things they like. The product attribute of this research consists of flavor, the volume, fat content and packaging type. Those four attributes were combined so that it forms stimuli. Nine main stimuli were generated. Total data and the average questionnaire results based on the attribute level are shown in Table 3 and based on stimuli are shown in Figure 1. According to Pelsmaeker et al. (2017), stimuli 3, stimuli 6 and stimuli 8 are considered as "neutral" or in another word, consumers have no preference towards those stimuli since their average score was in the range of 2.61 -3.41. Meanwhile, consumers' preference of other 6 stimuli was "like" as its average score was ranged from 3.41 -4.21. The average score of consumers' preference was then processed along with the dummy variable of formed stimuli to generate multiple regression equation.

Multiple Regression
Formed regression value functions to interpret the data of conjoint analysis by creating multiple regression equations to find the utility value of each attribute, the total utility value of each attribute, the importance value and relative attribute importance. Multiple regression equation formed is as follows: The calculation result based on the multiple regression equation was called prediction value. Prediction value indicates the amount of total utility value of each stimulus in the questionnaire. By knowing the total utility value, consumers' preference against attribute combination of taroflavored UHT Ultra milk (9 stimuli) can be figured out. Sumargo and Wardoyo (2008) argued that the formed regression equation would be used to calculate the value of each stimulus.

Data Processing Using Conjoint Method 1. Utility value of each attribute level
Utility value was obtained from the calculation using the regression coefficient in multiple regression equations. The calculation result of utility result of each attribute is as follows: a. Flavor attribute Flavor attribute is inspected using three-level samples; those are stronger milk flavor, balanced flavor between taro and milk and stronger taro flavor. The results of the research are shown in Figure 2.
Stronger taro flavor attribute level has the highest utility value of 0.095, which shows that consumers prefer strong taro flavor. However, the utility value of stronger milk flavor attribute level was -0.1327, which means that consumers dislike stronger milk flavor in taro-flavored UHT Ultra Milk. According to McCarthy et al. (2017), consumers dislike plain flavor in milk that tends to be fishy, too thick, too heavy, flavor and texture like cream, too fatty, and looks like half and half without any flavor. For this reason, specific kinds of flavor are added to remove that fishy flavor.

b. The volume attribute
Research of consumers' preference on the volume of content was performed under the volume of 125 mL, 200 mL, 250 mL. The results of the research are shown in Figure 3.
In Figure 3, it can be seen that the respondents prefer milk in 200 ml and dislike milk in 125 mL. This might happen as the respondents think that 125 mL is too little and unsatisfied when they consume it. For this reason, taro-flavored Ultra milk in volume of 200 mL was much preferred since they felt satisfied enough when consuming milk in this size. Meanwhile, drinking 250 mL of milk is too overwhelming for them. The calories it contains can influence consumers' satisfaction levels in consuming taro-flavored UHT Ultra milk. Each package of 200 mL of taro-flavored UHT Ultra milk may contain 130 kcal. Human's calorie intake is different depending on their gender. Our body's energy use will depend on how active we are, how efficiently our body uses the energy, and our age. According to the 2015-2020 Dietary Guidelines for Americans, women are likely to need between 1,600 and 2,400 calories a day, and men from 2,000 to 3,000 calories. However, this depends on their age, size, height, lifestyle, overall health, and activity level (Ismail, 2017).

c. Fat content attribute
To examine consumers' preference on the fat content attribute, fat and low fat chocolate-flavored UHT Ultra milk were used. The samples did not use taro-flavored UHT Ultra Milk since this variant is not available in low fat. The results of the research are shown in Figure 4.
For fat content levels, the respondents prefer low fat and dislike fatty levels. This might happen as the respondents feel that full fat milk tastes slightly sweeter than low fat milk. Different sweetness levels occur as low fat and full-fat milk has a different percentage of certain substance composition. Based on Frøst et al. (2001), a combination of thickener, whitener and cream aroma in 0.1% fat milk was approximately successful in mimicking sensory properties of 1.3% fat milk. It means that the taste of full-fat milk tends to be sweeter than low-fat milk.

d. Packaging type attribute
To examine consumers' preference on packaging type attribute, taro-flavored UHT Ultra Milk in tetrapack package and plastic bottle of other brands' milk products were used. The results of the research are shown in Figure 5.
Consumers prefer tetrapack packaging with a positive utility value of 0.092. Consumers dislike the use of plastic bottles. Perhaps, tetrapack was chosen by the consumers because it is eco-friendly and more aseptic than a plastic bottle. Kontominas (2010) stated that packaging is a major factor contributing to the quality and safety of milk because milk is a product which can spoil easily. Therefore, packaging technology plays an important part in extending its shelf-life.

Importance level and relative importance weight of each attribute
Attribute importance level is used to figure out the consumers' preference for a product attribute. From the importance level, relative importance weight can be obtained to figure out the attribute of taroflavored UHT Ultra milk, which becomes consumers' priority. The calculation results of the relative importance weight of each attribute are shown in Figure 6.
The importance weight of flavor attribute is relatively high, that is 34.44%. This indicates that consumers give more attention and prioritize flavor attributes in purchasing taro-flavored UHT Ultra milk products. The volume and packaging type attributes have the same relative importance weight that is 27.79%. Since these attributes have the same relative importance weight, both are considered important for consumers. The third priority attribute for consumers is the fat content, which is around 9.97%. It is because consumers purchasing taroflavored UHT Ultra milk products are mostly students or college students who prioritize taste, the volume of contents and affordable price rather than fat contents.

Total Utility Value of Each Stimuli of Taro-Flavored Uht Ultra Milk
The total utility value of each stimulus was calculated using the conjoint basic equation. Stimuli utility value was used to find out consumers' most preferred stimuli of 9 stimuli examined. Therefore, the conjoint basic equation formed is stated as follows:  Figure 7, it can be seen that the highest utility value of total stimuli was found in the fifth stimuli by 3.828. This showed that stimuli 5 was consumers' preferred stimuli. Stimuli 5 consisted of the combination of balanced flavor between milk and taro, the volume of 200 mL, low-fat content and tetrapack packaging. Overall, this stimuli combination is similar to the stimuli combination of taro-flavored UHT Ultra milk, which recently has spread over the current market. The difference is only on fat content.

Final validation of conjoint result
Final validation of the conjoint result used to draw the correlation between utility and actual utility. Final validation of the conjoint result was performed by using Kendall Tau correlation. Validation result is shown in Table 4.
The result of the table shows that the Kendall Tau correlation is as many as 0.889. The conjoint result has a real correlation with the respondents' opinion since it has a positive correlation. According to Kuzmanovic et al. (2011), if the correlation is positive, then there will be a positive correlation between conjoint results and respondents' opinions. According to Akoglu (2018), correlation result R. Pearson's and Kendall Tau is getting closer to 1. It is proven that there is a strong relationship between predicted utility and actual utility. Consumers' preference result on taro-flavored UHT Ultra Milk was obtained based on the attribute and stimuli level with the highest utility value. Based on the stimuli, consumers like stimuli 5 with the total utility value of 3.828. The results of consumer's preference are shown in Table 5. From 9 total utility value of each stimulus, the estimated average value was 3.623. According to Jervis et al. (2012), the result of the estimated average value interprets that the respondents "like" the formed stimuli. There are some differences in the flavor attribute in the chosen stimuli attribute levels and chosen attribute levels as it can be seen on Table 5. As a matter of fact, both levels were preferred by the respondents as they have positive utility value. Nonetheless, as a consequence of the simplification process in the stimuli formation using orthogonal arrays method, some attributes are not used in the research. As a result, some stimuli liked by the respondents are not included in the research. Sweet flavor also affects consumers' preference against milk flavor.

Conclusions
Based on the result and the data analysis of the research, it is concluded that the attribute importance level is sorted based on attribute relative importance weight. Therefore, the highest relative weight of the attribute becomes consumers' priority in buying taro-flavored UHT Ultra milk in Malang City, which is flavor with a relative weight of 34.44%. Furthermore, the attribute of volume of contents and packaging type, which has a similar relative weight, that is 27.79%. Consumers' last priority was fat content with its relative weight of 9.97%. Combination of consumers' most preferred attribute (stimuli) of 9 formed stimuli was found in the fifth stimuli with the total utility value of 3.828 which consists of balanced flavor between milk and taro with volume of contents of 200 ml, low in fat (low fat) and packaged in tetrapack. Consumers are interested in the latest innovation of the attribute combination of taro-flavored UHT Ultra milk. This condition indicates an opportunity for the company to improve its product with a new attribute combination.