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Economic and Consumer Acceptability of a Reconstituted Milk Product
Economic and Consumer Acceptability of a Reconstituted Milk Product G. D. WHIPPLE Department of Agricultural Economics and Rural Sociology P. M. D A V I D S O N and O. G. SANDERS Department of Food Technology and Science University of Tennessee P. O. Box 1071 Knoxville 37901--1071 ABSTRACT
We investigated consumer acceptability of reconstituted whole milk and estimated consumer demand response to change in price relationships between reconstituted fluid and fresh fluid milk. Sensory panelists tested five samples including 100% reconstituted whole milk, 100% fresh fluid milk, and 75:25, 50:50, and 25:75 blends of each. In a consumer home placement test, participants evaluated 100% reconstituted milk, 100% fresh milk, and a 50:50 blend. All five products in the laboratory panel were rated acceptable by inexperienced participants (48) whereas the 75 and 100% reconstituted samples were slightly unacceptable to persons (15) claiming experience in dairy products judging. Economic responses by laboratory taste panelists indicated they would pay an average of 16% less for reconstituted than fresh milk. Participants in the home placement test (303) rated the reconstituted samples significantly lower than the fresh fluid samples, but all mean sample scores were in the acceptable range. Cross-price elasticity estimates indicated that a reduction in the price of reconstituted milk by 1% would result in a 5% to 7.6% decrease in fresh fluid milk consumption. INTRODUCTION
Reconstituted fluid milk products are made by combining milk components (nonfat solids and milk fat) with potable water. The technology to reconstitute milk commercially has
Received June 3, 1982.
1983 J Dairy Sci. 66:381-389
been available, and reconstitution can be accomplished with the equipment in most modern dairy plants. Reconstituted fluid (RF) milk has been produced commercially in Alaska and on foreign military bases but has not received widespread use in the continental United States. Reconstituted fluid milk products have the potential of reducing costs of fluid milk in markets where milk must be transported long distances to satisfy consumption. Even though some markets in the US qualify under this criterion, state and federal market orders have prevented sale of RF milk products (2, 3). In September of 1979, the Consumer Nutrition Institute (CNI) petitioned the United States Department of Agriculture (USDA) for a hearing to review the federal market order pricing of RF milk products. The USDA ultimately turned down the request for a hearing, but the federal order pricing of RF milk remains an issue. The down allocation and compensatory payment provisions of the federal market orders (3) effectively prohibit the sale of RF products by pricing them higher than fresh fluid (FF) products. It was the intent of the CNI petition to relax these provisions to allow RF products to be priced at or below comparable FF products. Even if RF milk were priced competitively with FF milk, there is question Of consumer acceptability of RF milk. Reconstituted fluid milk would have a slightly different taste from FF milk because of the additional processing steps. The taste differences may make the RF milk an unacceptable substitute for FF milk. Herreid and Wilson (4) tested consumer acceptability of RF products with various contents of solids-not-fat and milk fat but did not evaluate the products in comparison to fresh fluid products. Otherwise, little substantive evidence exists of consumer acceptability of RF milk products. It was our purpose to investigate
381
382
WHIPPLE ET AL.
consumer acceptability of RF milk products and estimate consumers' demand response to a change in price relationships between RF and FF milk products. To satisfy these objectives, two consumer taste tests were conducted. The first, at the University of Tennessee (UT) Sensory Evaluation Laboratory, was intended to serve as a preliminary screening study to help in development of product samples and a survey questionnaire. The second, a home placement test, was intended to provide primary data for analysis. MATERIALS AND METHODS Preparation of Milk Samples
For the preliminary screening study, fresh whole milk was purchased from a local retail outlet. The milk product tested 3.25% fat and 8.40% MSNF (milk solids-not-fat) and was declared by an experienced dairy products judge to have no serious defects except a slight "feed" off-flavor. Reconstituted milk was prepared by combining a commercial instant nonfat dry milk with half-and-half (10.55% fat, 7.44% MSNF) and water. The final product tested 3.24% fat and 8.33% MSNF. Three blends of the two products then were prepared that contained 25% reconstituted: 75% fresh milk, 50% reconstituted: 50% fresh milk, and 75% reconstituted: 25% fresh milk. All blends were prepared the day before testing and stored at 4°C until used. Samples for consumer home placement testing were prepared at the UT Creamery. Raw
milk from the UT dairy herd was standardized to 3.31% fat and contained 8.32% MSNF. Products were homogenized at 140.6 kg/cm 2, pasteurized at 75°C for 16 s, and packaged in .946-liter plastic coated paper containers. The reconstituted product was formulated with Grade A low-heat nonfat dry milk powder, raw cream (41.11% fat, 5.42% MSNF), and potable water. Ingredients were mixed in a stainless steel vat to produce approximately 189.3 liters of product. The reconstituted milk then was processed and packaged with the same equipment and under the same conditions as the regular whole milk. The final tests on the reconstituted milk were fat 3.36% and MSNF 8.66%. A 50:50 blend of fresh and reconstituted milk was prepared by adding 94.6 liters of raw whole milk to 94.6 liters of the formulated reconstituted product and processing as before. Although the fat test for the blend approximated the other samples (3.02%), the MSNF was significantly lower (7.45%). The reason for this was most probably errors in the batch handling system and points to possible problems in a commercial process. Sensory Evaluation
A preliminary evaluation was on the acceptability of 100% reconstituted milk and the three blends of reconstituted milk and fresh milk (25:75; 50:50; 75:25) with 100% fresh milk as a reference. Tests were in the UT Food Technology and Science Sensory Evaluation Laboratory. Procedures and objectives of the test were within the guidelines outlined by
TABLE 1. Acceptability flavor scoresa of reconstituted milk, fresh milk, and blends by a laboratory taste panel. Percentage of reconstituted milk
Mean score, experienced judgesb
Mean score, nonexperienced judgesc
.X
SD
0 25 50 75 100
2.9d 2.3d 3.3d 4.1 d 4.3 d
2.9d 2.6d 2.9 d 2.8 e 3.2e
2.9 2.5 3.0 3.1 3.4
1.5 1.2 1.5 1.6 1.7
Overall
aseven- point scale where: 1 = like very much, 7 = dislike very much. b n=15. Cn = 48. d'eDifferent superscripts in the same row indicate significant differences (P<.05) by t test. Journal of Dairy Science Vol. 66, No. 3, 1983
ACCEPTANCE OF RECONSTITUTED MILK Sidel et al. (8) for affective tests in laboratory situations. The questionnaire asked the taster to evaluate each of the five samples for overall acceptability on a scale of 1 to 7 (1 = like very much and 7 = dislike very much). To determine !f experience in tasting dairy products influenced acceptability, a question on experience was included. For economic analysis, questions also were asked about the price the taster would pay for each product, the type of milk they normally used, and their income. Consumer testing in the home was used because this is an affective sensory test that evaluates acceptance under conditions approximating normal use (1, 6, 9). The consumer test involved evaluation of the 100% fresh milk, 100% reconstituted milk, and a 50:50 blend. A seven-page questionnaire and .946 liter of each of the three products were distributed to approximately 175 families in the Knoxville, TN area. Respondents were asked to test acceptability of the products under conditions normal for their family, complete the accompanying questionnaire, and return it in the stamped envelope. In addition to acceptability measures, other questions were asked about price, preference, milk usage, age, education, and income. Data Evaluation
Statistical analysis of sensory data was by analysis of variance, means, and t tests. RESULTS AND DISCUSSION Sensory-Evaluation
Laboratory. Sixty-three panelists participated in the laboratory or in-house sensory evaluation. Their responses on questionnaires indicated that 15 had experience judging dairy products and 48 had no experience. Experienced judges placed the 100% fresh fluid milk and 25% reconstituted sample between "like moderately" and "like slightly", and the 50% blend was rated between "neither like nor dislike" and "like slightly" (Table 1). Also, experienced judges rated the 75 and 100% reconstituted samples as slightly unacceptable (between "neither like nor dislike" and "dislike slightly"). Inexperienced judges rated all but the 100% reconstituted sample in the "like moderately" to "like slightly" range.
38 3
Although overall mean scores were within acceptable range, analysis of variance revealed that there was a significant difference (P<.05) among scores of individual samples. Experience in tasting dairy products also had a significant effect (P<.01) on scores assigned each sample. By t test, differences were significant for ratings given the 75 and 100% reconstituted samples by the experienced and nonexperienced panelists (Table 1). To measure the economic acceptability of RF milk products, participants in the laboratory evaluation were asked to estimate how much they would pay for 3.785 liters of each of the sample products if the milk they normally consume were priced at $2 per 3.785 liters. The difference between the consumer's estimated sample price and $2 indicated the price differential necessary to induce the consumer to switch to the sample milk product. The participant responses for each of the five sample products are listed in Table 2. About 4% of the participants priced the RF sample above $2, indicating preference for the RF sample product over milk used at home, and on the average, 32% indicated no preference for either. The mean percentage price difference necessary to induce panelists to consume the reconstituted sample rather than the milk they use at home averaged about 16% over the four RF blend samples. A t test for differences among sample means indicated that the 25% RF sample had a mean price difference significantly lower (P<.05) than the other samples. There were no significant differences among other sample means. Participants preferred the 25% RF sample over the 100% FF milk sample. The final column of Table 2 lists an aggregate estimate of the cross-price elasticity of demand between the RF sample and the milk the consumer normally used at home. This estimate might more accurately be called a cross-price quantity response. It is the percentage change in the quantity of FF milk that would be utilized in response to a 1% change in-the price of the RF milk product, other factors constant. This estimate is the negative percentage of RF milk in the product sample divided by the percentage price difference necessary to induce the participant to consume the RF product. The cross-elasticity estimate averaged nearly 4 over all RF samples, indicating that a 1% reduction in the price of RF milk would induce Journal of Dairy Science Vol. 66, No. 3, 1983
00
~7 TABLE 2. Preferences and price difference responses of the laboratory taste panel participants for reconstituted and fresh milk samples. <
Mean price difference necessary to induce participants to purchase the sample milk rather than the milk used at h o m e
O O~ Ox
Z
Q
t~
Sample
Participants who preferred sample to milk used at h o m e
Participants with no preference between the sample and milk used at home
00
The change in the q u a n t i t y of fresh fluid milk consumed in response to a 1% change in the price of the reconstituted fluid milk sample
(%) 100% Fresh milk
3.28
39.24
25:75 b Blend
3.28
39.68
50:50 Blend
4.92
26.70
75:25 Blend
4.92
33.33
100% Reconstituted
3.28
28.57
All reconstituted blend samples
3.97
32.14
-16.63 (29.20) a - 8.15" (15.89) -16.34 (28.48) --17.86 (29.41) --22.41 (32.62) -16.34 (27.62)
aThis is the standard deviation about the associated mean. b T h e n u m b e r s represent the percentage of fresh milk and reconstituted milk, respectively, in t h e sample. *Significant for P<.05.
3.07 3.06 4.20 4.46
3.83
t"
ACCEPTANCE OF RECONSTITUTED MILK a 4% decrease in the a m o u n t of F F m i l k consumed with an a c c o m p a n y i n g 4% increase in the use o f R F fluid milk. If a unit of R F p r o d u c t substitutes for a unit of F F product, the total direct price effect o f a R F m i l k price decrease includes the p r o d u c t d e m a n d transfer f r o m F F milk d e m a n d due to the close subsfitutabiliry of R F and F F products, plus o t h e r goods substitution effects and i n c o m e effects. Consumer H o m e Placement. Samples were distributed to a p p r o x i m a t e l y 175 families. Of those families, 107 (61.1%) returned a completed questionnaire. The average size of families in the study was 3.4 members. A total of 303 individuals t o o k part in the study; this a c c o u n t e d for 82.6% of the total n u m b e r of individuals residing in the households. O f the individuals indicating their sex, 139 (48.1%) were females and 150 (51.9%) were males. Ages ranged f r o m 2 to 82 with a m e a n of 28.9 y r (Table 3). The largest single age group was 4 yr olds (n = 12). The average e d u c a t i o n of heads of h o u s e h o l d s was " s o m e college". S o m e 94.4% (101) of families used m i l k as beverage, 93.5% (100) used it in baking or cooking, 93.5% (100) on cereals, 43.0% ( 4 6 ) i n coffee or tea, and 7.5% (8) indicated o t h e r uses. T h e m a j o r t y p e o f milk used was t o w f a t (76.6%) with w h o l e (24.3%), skim (13.1%), n o n f a t dry milk (7.5%) following. All of the households indicated t h e y used m i l k in s o m e form. T h e average a m o u n t of m i l k purchased per w e e k per family was estimated tO be 7.9 liters. Mean scores o f t h e F F , R F , and 5 0 : 5 0 blend samples were 2.31, 2.68, and 2.71 (Table 4). On the seven p o i n t scale, these scores all rated b e t w e e n "like m o d e r a t e l y " and "like slightly", which indicated t h a t the samples were, on the average, acceptable to consumers. Further, o n l y 58 of 895 taste tests resulted in rejection scores of 6 ("dislike m o d e r a t e l y " ) and 7 ("dislike very m u c h " ) . O f the 58 l o w scores, 16 were regular whole milk, 15 were the blend, and 27 were t h e 100% r e c o n s t i t u t e d sample. There was a significant difference (P<.01) a m o n g m e a n flavor scores assigned to the three saml~les by each family. Factors t h a t affected the m e a n flavor score by family were t y p e o f sample ( P < . 0 5 ) and use o f w h o l e milk as the primary t y p e of milk in the h o m e (P<.01) (Table 5). F o r families that normally used whole m i l k as their primary beverage, the
3 85
TABLE 3. Number of individuals in each age group participating in the home placement study. Age
Number
10 and under 11 19 20 -- 30 31 -- 45 46 -- 6O over 60 Total -
Percentage
53 40 76 78 44 9 300
17.7 13.3 25.3 26.0 14.7 3.0
TABLE 4. Acceptability flavor scoresa of reconstituted milk, fresh milk, and a 50:50 blend assigned by individuals in the consumer home placement study. Mean flavor
Sample
n
score
SD
Fresh milk 50:50 Reconstituted milk
302 298 295
2.31 2.70 2.68
1.50 1.47 1.79
aseven point scale where: I = like very much, 7 = dislike very much.
TABLE 5. Analysis of variance for flavor scores by familya and individuals in families. Source By family a Milk type Whole milk use Lowfat milk use Skim milk use NFDM use Education Error By individual Milk type Age Age * sex Error
df
MS
F
2 1 1 1 1 5 308
6.32 12.50 1.82 .63 1.04 4.52 1.78
3.55* 7.02* 1.02 .36 .58 .51 ....
2 64 49
12.13 3.01 3.33 2.42
5.02* 1.24 1.38" ....
737
ascores for families were calculated by taking the mean score for all family members. *Significant for P<.05. Journal of Dairy Science Vol. 66, No. 3, 1983
O0 Ox
t~
D,
<
Q
TABLE 6. Preference and price difference responses of home placement participants for the fresh and reconstituted milk samples in comparison to the milk they normally used at home.
Ox
Z .o
Sample
Participants who preferred sample to milk used at home
Mean price difference which would induce participants to purchase sample milk rather than milk used at home
Participants who had no preference between product sample and milk used at home
Change in quantity of fresh fluid milk consumed in response to ~ 1% change in price of product sample containing reconstituted fluid milk
(%) 100% Fresh milk
8.9
37.6
50:50 Blend
9.9
38.6
100% Reconstituted milk
11.2
39.8
All reconstituted samples
10.6
39.2
astandard deviation,
-14.73 (27.12) a --14.58 (27.19) --14,98 (29.47) -14.77 (28.26)
.... 3.32 6.68 5.05
w
ACCEPTANCE OF RECONSTITUTED MILK
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E
E
o o 0.,
0
o g'~
. ~ o ~
0 Ca.
o 0
E
.~ ~ ~ ~-~,, ox
O
~-
e~ e~
~z M
<
e~
°
o
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38 7
overall score for all samples was 2.87. In contrast, families who normally did not consume whole milk rated all the samples significantly better with a score of 2.40. The use o f lowfat, skim, or nonfat dry milk as well as education had no effect on assigned flavor scores. Scores assigned by individuals were affected only by sample and the age-sex interaction (Table 5). Although the age-sex interaction was significant, there were no clear trends for this variation source. The individual's sex had no significant effect on flavor scores. As in laboratory taste panel test, participants in the home placement taste test were asked to indicate a price that would induce them to consume the sample milk rather than the milk they normally use, priced at $2 per 3.785 liters. Participants' responses to this question are in Table 6. Overall, more than 10% of the participants priced the R F samples above $2, indicating preference for the R F sample milk over the milk used at home. Over 39% priced the R F products at $2 indicating indifference between R F products and milk used at home. On the average, a 14.77% price difference would be required to induce participants to purchase the R F sample milk rather than the milk they used at home. However, a t test indicated no significant differences between mean percentage price differences for the F F sample and R F sample (P<.05). The overall cross-price elasticity estimate was 5.05, indicating that a 1% reduction in the price of R F milk would induce a 5% decrease in the quantity of F F milk consumed with an accompanying increase in the use of R F milk. To compare the consumeg's relative preferences among the three samples, it first was assumed that the 100% fresh milk sample was the product the participant normally used. The price preferences then were compared to the 100% fresh milk sample (Table 7). Nearly 25% of the participants priced the R F samples higher than the F F milk sample and nearly 38% priced them the same. The mean percentage price difference that would induce use of the R F samples rather than the 100% F F sample was 9.8%. By t test, no significant difference between the mean price percentage differences for the 50 and 100% R F samples was found (P<.05). The cross-price elasticity estimate indicated that a 1% reduction in the price of Journal of Dairy Science Vol. 66, No. 3, 1983
388
WHIPPLE ET AL.
RF milk would result in a 7.6% reduction in the quantity of FF milk consumed. CONCLUSIONS
Results of the two consumer taste tests of RF milk products do not support the hypothesis that RF milk is an unacceptable substitute for FF milk. Flavor score data indicated that even though, on the average, participants rated samples containing RF milk below the 100% fresh samples, all of the samples were rated acceptable. Participant responses to the pricing questions indicated a preference for the milk the consumer normally used over all of the samples, but little preference for the FF sample over the RF samples. It appears that in samples containing half or less RF milk the participants did not find the slightly cooked flavor of the RF sample undesirable or were not able to detect it. Although the results do not indicate a strong preference for RF blends over the 100% RF product, blending RF and FF milk seems to be a way to introduce a substantial amount of RF milk onto a market with a product tasting similar to fresh milk. In fact, the 25% RF sample was preferred by the sensory laboratory test participants both with and without training in dairy products tasting. A pair of caveats are associated with the taste tests for these results. All of the samples, both FF and RF, were standardized with fat consistent with whole milk. Survey data indicate the majority (76%) of the participants normally consumed lowfat milk. Analysis of flavor score data indicated that significantly lower flavor scores were assigned to all of the product samples by persons who normally drank whole milk. The reason for this is unknown, but a possible explanation is that it may reflect the preference of participants for fat in milk. Participants accustomed to lowfat or skim milk may have rated the samples higher because of their preference for, but infamiliarity with, the relatively high fat of the samples. The second caveat is associated with the low MSNF in the 50:50 blend sample in the home placement test. Hillman et al. (5)found that variation of .5% fat and 1.0% MSNF in beverage milk could be detected by consumers, and Pangborn and Dunkley (7) reported that MSNF content had a greater effect on consumer acceptability than did fat content. The low MSNF in the Journal of Dairy Science Vol. 66, No. 3, 1983
50:50 blend sample may explain its low rating relative to the 100% F F sample and its similar rating to the 100% RF sample. It is risky to apply results such as these to predict actions of the consuming population, because the participants were not selected randomly. Even so, a wide range of income and education characteristics were included in the participant group, and it is the opinion of the authors that the participants were representative of consumers in the Knoxville, TN area. If one accepts these results as representative of consumer preferences across the US, a change in market order provisions so that RF milk could be sold at prices below those of fresh milk could have a substantial impact on the way milk is marketed. For each 1% reduction in file price of RF milk below the price of F F milk, approximately 5% of fluid milk sales would shift from fresh to reconstituted products. A 5% price difference (which is in the range of potential change) would result in a 25% market shift to RF products. ACKNOWLEDGMENTS
We thank H. O. Jaynes for his technical expertise and H. N. Carringer for his help in preparing the samples. This research was supported by USDA Southern Regional Research Project S - 1 6 6 and the Agricultural Experiment Station at the University of Tennessee. REFERENCES
1 ASTM. 1979. ASTM manual on consumers sensory evaluation. STP 682. Amer. Soc. Testing Mater. Comm. E--18. Philadelphia, PA. 2 Hallberg, M. C., and R. A. King. 1980. Pricing of milk and dairy products. Pennsylvania State Univ. Agric. Exp. Stn. Agric. Rural Soc. 150. 3 Hammond, J. W., B. W. BuxtOn, and C. S. Thraen. 1979. Potential impacts of reconstituted milk on regional prices, utilization and production. Upiv. Minnesota Agric. Exp. Sin. Bull. 519. 4 Herreid, E. O., and H. K. Wilson. 1967. Milk fortification and reconstitution with solids-not-fat. Univ. Illinois Dep. Agric. Econ. Bull. No. 14. 5 Hillman, U.S., J. W. Stull, and R. S. Angus. 1963. Consumer preferences acceptance for milk varying in fat and solids-not-fat. Arizona Agric. Exp. Stu. Tech. Bull. 153. 6 Institute of Food Technologists, Sensory Evaluation Division. 1981. Sensory evaluation guide for testing food and beverage products. Food Technol. 35:50. 7 Pangborn, R. M., and W. L. Dunkley. 1964. Sensory
ACCEPTANCE OF RECONSTITUTED MILK discrimination of fat and solids-not-fat in milk. J. Dairy Sci. 47:719. Sidel, J. L., H. Stone, and J. Bloomquist. 1981. Use and misuse of sensory evaluation in research
389
and quality control. J. Dairy Sci. 64:2296. Warwick, D. P., and C. A. Lininger. 1975. The sample survey: theory and practice. McGraw-Hill, Inc. New York, NY.
Journal of Dairy Science Vol. 66, No. 3, 1983
We investigated consumer acceptability of reconstituted whole milk and estimated consumer demand response to change in price relationships between reconstituted fluid and fresh fluid milk. Sensory panelists tested five samples including 100% reconstituted whole milk, 100% fresh fluid milk, and 75:25, 50:50, and 25:75 blends of each. In a consumer home placement test, participants evaluated 100% reconstituted milk, 100% fresh milk, and a 50:50 blend. All five products in the laboratory panel were rated acceptable by inexperienced participants (48) whereas the 75 and 100% reconstituted samples were slightly unacceptable to persons (15) claiming experience in dairy products judging. Economic responses by laboratory taste panelists indicated they would pay an average of 16% less for reconstituted than fresh milk. Participants in the home placement test (303) rated the reconstituted samples significantly lower than the fresh fluid samples, but all mean sample scores were in the acceptable range. Cross-price elasticity estimates indicated that a reduction in the price of reconstituted milk by 1% would result in a 5% to 7.6% decrease in fresh fluid milk consumption. INTRODUCTION
Reconstituted fluid milk products are made by combining milk components (nonfat solids and milk fat) with potable water. The technology to reconstitute milk commercially has
Received June 3, 1982.
1983 J Dairy Sci. 66:381-389
been available, and reconstitution can be accomplished with the equipment in most modern dairy plants. Reconstituted fluid (RF) milk has been produced commercially in Alaska and on foreign military bases but has not received widespread use in the continental United States. Reconstituted fluid milk products have the potential of reducing costs of fluid milk in markets where milk must be transported long distances to satisfy consumption. Even though some markets in the US qualify under this criterion, state and federal market orders have prevented sale of RF milk products (2, 3). In September of 1979, the Consumer Nutrition Institute (CNI) petitioned the United States Department of Agriculture (USDA) for a hearing to review the federal market order pricing of RF milk products. The USDA ultimately turned down the request for a hearing, but the federal order pricing of RF milk remains an issue. The down allocation and compensatory payment provisions of the federal market orders (3) effectively prohibit the sale of RF products by pricing them higher than fresh fluid (FF) products. It was the intent of the CNI petition to relax these provisions to allow RF products to be priced at or below comparable FF products. Even if RF milk were priced competitively with FF milk, there is question Of consumer acceptability of RF milk. Reconstituted fluid milk would have a slightly different taste from FF milk because of the additional processing steps. The taste differences may make the RF milk an unacceptable substitute for FF milk. Herreid and Wilson (4) tested consumer acceptability of RF products with various contents of solids-not-fat and milk fat but did not evaluate the products in comparison to fresh fluid products. Otherwise, little substantive evidence exists of consumer acceptability of RF milk products. It was our purpose to investigate
381
382
WHIPPLE ET AL.
consumer acceptability of RF milk products and estimate consumers' demand response to a change in price relationships between RF and FF milk products. To satisfy these objectives, two consumer taste tests were conducted. The first, at the University of Tennessee (UT) Sensory Evaluation Laboratory, was intended to serve as a preliminary screening study to help in development of product samples and a survey questionnaire. The second, a home placement test, was intended to provide primary data for analysis. MATERIALS AND METHODS Preparation of Milk Samples
For the preliminary screening study, fresh whole milk was purchased from a local retail outlet. The milk product tested 3.25% fat and 8.40% MSNF (milk solids-not-fat) and was declared by an experienced dairy products judge to have no serious defects except a slight "feed" off-flavor. Reconstituted milk was prepared by combining a commercial instant nonfat dry milk with half-and-half (10.55% fat, 7.44% MSNF) and water. The final product tested 3.24% fat and 8.33% MSNF. Three blends of the two products then were prepared that contained 25% reconstituted: 75% fresh milk, 50% reconstituted: 50% fresh milk, and 75% reconstituted: 25% fresh milk. All blends were prepared the day before testing and stored at 4°C until used. Samples for consumer home placement testing were prepared at the UT Creamery. Raw
milk from the UT dairy herd was standardized to 3.31% fat and contained 8.32% MSNF. Products were homogenized at 140.6 kg/cm 2, pasteurized at 75°C for 16 s, and packaged in .946-liter plastic coated paper containers. The reconstituted product was formulated with Grade A low-heat nonfat dry milk powder, raw cream (41.11% fat, 5.42% MSNF), and potable water. Ingredients were mixed in a stainless steel vat to produce approximately 189.3 liters of product. The reconstituted milk then was processed and packaged with the same equipment and under the same conditions as the regular whole milk. The final tests on the reconstituted milk were fat 3.36% and MSNF 8.66%. A 50:50 blend of fresh and reconstituted milk was prepared by adding 94.6 liters of raw whole milk to 94.6 liters of the formulated reconstituted product and processing as before. Although the fat test for the blend approximated the other samples (3.02%), the MSNF was significantly lower (7.45%). The reason for this was most probably errors in the batch handling system and points to possible problems in a commercial process. Sensory Evaluation
A preliminary evaluation was on the acceptability of 100% reconstituted milk and the three blends of reconstituted milk and fresh milk (25:75; 50:50; 75:25) with 100% fresh milk as a reference. Tests were in the UT Food Technology and Science Sensory Evaluation Laboratory. Procedures and objectives of the test were within the guidelines outlined by
TABLE 1. Acceptability flavor scoresa of reconstituted milk, fresh milk, and blends by a laboratory taste panel. Percentage of reconstituted milk
Mean score, experienced judgesb
Mean score, nonexperienced judgesc
.X
SD
0 25 50 75 100
2.9d 2.3d 3.3d 4.1 d 4.3 d
2.9d 2.6d 2.9 d 2.8 e 3.2e
2.9 2.5 3.0 3.1 3.4
1.5 1.2 1.5 1.6 1.7
Overall
aseven- point scale where: 1 = like very much, 7 = dislike very much. b n=15. Cn = 48. d'eDifferent superscripts in the same row indicate significant differences (P<.05) by t test. Journal of Dairy Science Vol. 66, No. 3, 1983
ACCEPTANCE OF RECONSTITUTED MILK Sidel et al. (8) for affective tests in laboratory situations. The questionnaire asked the taster to evaluate each of the five samples for overall acceptability on a scale of 1 to 7 (1 = like very much and 7 = dislike very much). To determine !f experience in tasting dairy products influenced acceptability, a question on experience was included. For economic analysis, questions also were asked about the price the taster would pay for each product, the type of milk they normally used, and their income. Consumer testing in the home was used because this is an affective sensory test that evaluates acceptance under conditions approximating normal use (1, 6, 9). The consumer test involved evaluation of the 100% fresh milk, 100% reconstituted milk, and a 50:50 blend. A seven-page questionnaire and .946 liter of each of the three products were distributed to approximately 175 families in the Knoxville, TN area. Respondents were asked to test acceptability of the products under conditions normal for their family, complete the accompanying questionnaire, and return it in the stamped envelope. In addition to acceptability measures, other questions were asked about price, preference, milk usage, age, education, and income. Data Evaluation
Statistical analysis of sensory data was by analysis of variance, means, and t tests. RESULTS AND DISCUSSION Sensory-Evaluation
Laboratory. Sixty-three panelists participated in the laboratory or in-house sensory evaluation. Their responses on questionnaires indicated that 15 had experience judging dairy products and 48 had no experience. Experienced judges placed the 100% fresh fluid milk and 25% reconstituted sample between "like moderately" and "like slightly", and the 50% blend was rated between "neither like nor dislike" and "like slightly" (Table 1). Also, experienced judges rated the 75 and 100% reconstituted samples as slightly unacceptable (between "neither like nor dislike" and "dislike slightly"). Inexperienced judges rated all but the 100% reconstituted sample in the "like moderately" to "like slightly" range.
38 3
Although overall mean scores were within acceptable range, analysis of variance revealed that there was a significant difference (P<.05) among scores of individual samples. Experience in tasting dairy products also had a significant effect (P<.01) on scores assigned each sample. By t test, differences were significant for ratings given the 75 and 100% reconstituted samples by the experienced and nonexperienced panelists (Table 1). To measure the economic acceptability of RF milk products, participants in the laboratory evaluation were asked to estimate how much they would pay for 3.785 liters of each of the sample products if the milk they normally consume were priced at $2 per 3.785 liters. The difference between the consumer's estimated sample price and $2 indicated the price differential necessary to induce the consumer to switch to the sample milk product. The participant responses for each of the five sample products are listed in Table 2. About 4% of the participants priced the RF sample above $2, indicating preference for the RF sample product over milk used at home, and on the average, 32% indicated no preference for either. The mean percentage price difference necessary to induce panelists to consume the reconstituted sample rather than the milk they use at home averaged about 16% over the four RF blend samples. A t test for differences among sample means indicated that the 25% RF sample had a mean price difference significantly lower (P<.05) than the other samples. There were no significant differences among other sample means. Participants preferred the 25% RF sample over the 100% FF milk sample. The final column of Table 2 lists an aggregate estimate of the cross-price elasticity of demand between the RF sample and the milk the consumer normally used at home. This estimate might more accurately be called a cross-price quantity response. It is the percentage change in the quantity of FF milk that would be utilized in response to a 1% change in-the price of the RF milk product, other factors constant. This estimate is the negative percentage of RF milk in the product sample divided by the percentage price difference necessary to induce the participant to consume the RF product. The cross-elasticity estimate averaged nearly 4 over all RF samples, indicating that a 1% reduction in the price of RF milk would induce Journal of Dairy Science Vol. 66, No. 3, 1983
00
~7 TABLE 2. Preferences and price difference responses of the laboratory taste panel participants for reconstituted and fresh milk samples. <
Mean price difference necessary to induce participants to purchase the sample milk rather than the milk used at h o m e
O O~ Ox
Z
Q
t~
Sample
Participants who preferred sample to milk used at h o m e
Participants with no preference between the sample and milk used at home
00
The change in the q u a n t i t y of fresh fluid milk consumed in response to a 1% change in the price of the reconstituted fluid milk sample
(%) 100% Fresh milk
3.28
39.24
25:75 b Blend
3.28
39.68
50:50 Blend
4.92
26.70
75:25 Blend
4.92
33.33
100% Reconstituted
3.28
28.57
All reconstituted blend samples
3.97
32.14
-16.63 (29.20) a - 8.15" (15.89) -16.34 (28.48) --17.86 (29.41) --22.41 (32.62) -16.34 (27.62)
aThis is the standard deviation about the associated mean. b T h e n u m b e r s represent the percentage of fresh milk and reconstituted milk, respectively, in t h e sample. *Significant for P<.05.
3.07 3.06 4.20 4.46
3.83
t"
ACCEPTANCE OF RECONSTITUTED MILK a 4% decrease in the a m o u n t of F F m i l k consumed with an a c c o m p a n y i n g 4% increase in the use o f R F fluid milk. If a unit of R F p r o d u c t substitutes for a unit of F F product, the total direct price effect o f a R F m i l k price decrease includes the p r o d u c t d e m a n d transfer f r o m F F milk d e m a n d due to the close subsfitutabiliry of R F and F F products, plus o t h e r goods substitution effects and i n c o m e effects. Consumer H o m e Placement. Samples were distributed to a p p r o x i m a t e l y 175 families. Of those families, 107 (61.1%) returned a completed questionnaire. The average size of families in the study was 3.4 members. A total of 303 individuals t o o k part in the study; this a c c o u n t e d for 82.6% of the total n u m b e r of individuals residing in the households. O f the individuals indicating their sex, 139 (48.1%) were females and 150 (51.9%) were males. Ages ranged f r o m 2 to 82 with a m e a n of 28.9 y r (Table 3). The largest single age group was 4 yr olds (n = 12). The average e d u c a t i o n of heads of h o u s e h o l d s was " s o m e college". S o m e 94.4% (101) of families used m i l k as beverage, 93.5% (100) used it in baking or cooking, 93.5% (100) on cereals, 43.0% ( 4 6 ) i n coffee or tea, and 7.5% (8) indicated o t h e r uses. T h e m a j o r t y p e o f milk used was t o w f a t (76.6%) with w h o l e (24.3%), skim (13.1%), n o n f a t dry milk (7.5%) following. All of the households indicated t h e y used m i l k in s o m e form. T h e average a m o u n t of m i l k purchased per w e e k per family was estimated tO be 7.9 liters. Mean scores o f t h e F F , R F , and 5 0 : 5 0 blend samples were 2.31, 2.68, and 2.71 (Table 4). On the seven p o i n t scale, these scores all rated b e t w e e n "like m o d e r a t e l y " and "like slightly", which indicated t h a t the samples were, on the average, acceptable to consumers. Further, o n l y 58 of 895 taste tests resulted in rejection scores of 6 ("dislike m o d e r a t e l y " ) and 7 ("dislike very m u c h " ) . O f the 58 l o w scores, 16 were regular whole milk, 15 were the blend, and 27 were t h e 100% r e c o n s t i t u t e d sample. There was a significant difference (P<.01) a m o n g m e a n flavor scores assigned to the three saml~les by each family. Factors t h a t affected the m e a n flavor score by family were t y p e o f sample ( P < . 0 5 ) and use o f w h o l e milk as the primary t y p e of milk in the h o m e (P<.01) (Table 5). F o r families that normally used whole m i l k as their primary beverage, the
3 85
TABLE 3. Number of individuals in each age group participating in the home placement study. Age
Number
10 and under 11 19 20 -- 30 31 -- 45 46 -- 6O over 60 Total -
Percentage
53 40 76 78 44 9 300
17.7 13.3 25.3 26.0 14.7 3.0
TABLE 4. Acceptability flavor scoresa of reconstituted milk, fresh milk, and a 50:50 blend assigned by individuals in the consumer home placement study. Mean flavor
Sample
n
score
SD
Fresh milk 50:50 Reconstituted milk
302 298 295
2.31 2.70 2.68
1.50 1.47 1.79
aseven point scale where: I = like very much, 7 = dislike very much.
TABLE 5. Analysis of variance for flavor scores by familya and individuals in families. Source By family a Milk type Whole milk use Lowfat milk use Skim milk use NFDM use Education Error By individual Milk type Age Age * sex Error
df
MS
F
2 1 1 1 1 5 308
6.32 12.50 1.82 .63 1.04 4.52 1.78
3.55* 7.02* 1.02 .36 .58 .51 ....
2 64 49
12.13 3.01 3.33 2.42
5.02* 1.24 1.38" ....
737
ascores for families were calculated by taking the mean score for all family members. *Significant for P<.05. Journal of Dairy Science Vol. 66, No. 3, 1983
O0 Ox
t~
D,
<
Q
TABLE 6. Preference and price difference responses of home placement participants for the fresh and reconstituted milk samples in comparison to the milk they normally used at home.
Ox
Z .o
Sample
Participants who preferred sample to milk used at home
Mean price difference which would induce participants to purchase sample milk rather than milk used at home
Participants who had no preference between product sample and milk used at home
Change in quantity of fresh fluid milk consumed in response to ~ 1% change in price of product sample containing reconstituted fluid milk
(%) 100% Fresh milk
8.9
37.6
50:50 Blend
9.9
38.6
100% Reconstituted milk
11.2
39.8
All reconstituted samples
10.6
39.2
astandard deviation,
-14.73 (27.12) a --14.58 (27.19) --14,98 (29.47) -14.77 (28.26)
.... 3.32 6.68 5.05
w
ACCEPTANCE OF RECONSTITUTED MILK
~
E
E
o o 0.,
0
o g'~
. ~ o ~
0 Ca.
o 0
E
.~ ~ ~ ~-~,, ox
O
~-
e~ e~
~z M
<
e~
°
o
E o
38 7
overall score for all samples was 2.87. In contrast, families who normally did not consume whole milk rated all the samples significantly better with a score of 2.40. The use o f lowfat, skim, or nonfat dry milk as well as education had no effect on assigned flavor scores. Scores assigned by individuals were affected only by sample and the age-sex interaction (Table 5). Although the age-sex interaction was significant, there were no clear trends for this variation source. The individual's sex had no significant effect on flavor scores. As in laboratory taste panel test, participants in the home placement taste test were asked to indicate a price that would induce them to consume the sample milk rather than the milk they normally use, priced at $2 per 3.785 liters. Participants' responses to this question are in Table 6. Overall, more than 10% of the participants priced the R F samples above $2, indicating preference for the R F sample milk over the milk used at home. Over 39% priced the R F products at $2 indicating indifference between R F products and milk used at home. On the average, a 14.77% price difference would be required to induce participants to purchase the R F sample milk rather than the milk they used at home. However, a t test indicated no significant differences between mean percentage price differences for the F F sample and R F sample (P<.05). The overall cross-price elasticity estimate was 5.05, indicating that a 1% reduction in the price of R F milk would induce a 5% decrease in the quantity of F F milk consumed with an accompanying increase in the use of R F milk. To compare the consumeg's relative preferences among the three samples, it first was assumed that the 100% fresh milk sample was the product the participant normally used. The price preferences then were compared to the 100% fresh milk sample (Table 7). Nearly 25% of the participants priced the R F samples higher than the F F milk sample and nearly 38% priced them the same. The mean percentage price difference that would induce use of the R F samples rather than the 100% F F sample was 9.8%. By t test, no significant difference between the mean price percentage differences for the 50 and 100% R F samples was found (P<.05). The cross-price elasticity estimate indicated that a 1% reduction in the price of Journal of Dairy Science Vol. 66, No. 3, 1983
388
WHIPPLE ET AL.
RF milk would result in a 7.6% reduction in the quantity of FF milk consumed. CONCLUSIONS
Results of the two consumer taste tests of RF milk products do not support the hypothesis that RF milk is an unacceptable substitute for FF milk. Flavor score data indicated that even though, on the average, participants rated samples containing RF milk below the 100% fresh samples, all of the samples were rated acceptable. Participant responses to the pricing questions indicated a preference for the milk the consumer normally used over all of the samples, but little preference for the FF sample over the RF samples. It appears that in samples containing half or less RF milk the participants did not find the slightly cooked flavor of the RF sample undesirable or were not able to detect it. Although the results do not indicate a strong preference for RF blends over the 100% RF product, blending RF and FF milk seems to be a way to introduce a substantial amount of RF milk onto a market with a product tasting similar to fresh milk. In fact, the 25% RF sample was preferred by the sensory laboratory test participants both with and without training in dairy products tasting. A pair of caveats are associated with the taste tests for these results. All of the samples, both FF and RF, were standardized with fat consistent with whole milk. Survey data indicate the majority (76%) of the participants normally consumed lowfat milk. Analysis of flavor score data indicated that significantly lower flavor scores were assigned to all of the product samples by persons who normally drank whole milk. The reason for this is unknown, but a possible explanation is that it may reflect the preference of participants for fat in milk. Participants accustomed to lowfat or skim milk may have rated the samples higher because of their preference for, but infamiliarity with, the relatively high fat of the samples. The second caveat is associated with the low MSNF in the 50:50 blend sample in the home placement test. Hillman et al. (5)found that variation of .5% fat and 1.0% MSNF in beverage milk could be detected by consumers, and Pangborn and Dunkley (7) reported that MSNF content had a greater effect on consumer acceptability than did fat content. The low MSNF in the Journal of Dairy Science Vol. 66, No. 3, 1983
50:50 blend sample may explain its low rating relative to the 100% F F sample and its similar rating to the 100% RF sample. It is risky to apply results such as these to predict actions of the consuming population, because the participants were not selected randomly. Even so, a wide range of income and education characteristics were included in the participant group, and it is the opinion of the authors that the participants were representative of consumers in the Knoxville, TN area. If one accepts these results as representative of consumer preferences across the US, a change in market order provisions so that RF milk could be sold at prices below those of fresh milk could have a substantial impact on the way milk is marketed. For each 1% reduction in file price of RF milk below the price of F F milk, approximately 5% of fluid milk sales would shift from fresh to reconstituted products. A 5% price difference (which is in the range of potential change) would result in a 25% market shift to RF products. ACKNOWLEDGMENTS
We thank H. O. Jaynes for his technical expertise and H. N. Carringer for his help in preparing the samples. This research was supported by USDA Southern Regional Research Project S - 1 6 6 and the Agricultural Experiment Station at the University of Tennessee. REFERENCES
1 ASTM. 1979. ASTM manual on consumers sensory evaluation. STP 682. Amer. Soc. Testing Mater. Comm. E--18. Philadelphia, PA. 2 Hallberg, M. C., and R. A. King. 1980. Pricing of milk and dairy products. Pennsylvania State Univ. Agric. Exp. Stn. Agric. Rural Soc. 150. 3 Hammond, J. W., B. W. BuxtOn, and C. S. Thraen. 1979. Potential impacts of reconstituted milk on regional prices, utilization and production. Upiv. Minnesota Agric. Exp. Sin. Bull. 519. 4 Herreid, E. O., and H. K. Wilson. 1967. Milk fortification and reconstitution with solids-not-fat. Univ. Illinois Dep. Agric. Econ. Bull. No. 14. 5 Hillman, U.S., J. W. Stull, and R. S. Angus. 1963. Consumer preferences acceptance for milk varying in fat and solids-not-fat. Arizona Agric. Exp. Stu. Tech. Bull. 153. 6 Institute of Food Technologists, Sensory Evaluation Division. 1981. Sensory evaluation guide for testing food and beverage products. Food Technol. 35:50. 7 Pangborn, R. M., and W. L. Dunkley. 1964. Sensory
ACCEPTANCE OF RECONSTITUTED MILK discrimination of fat and solids-not-fat in milk. J. Dairy Sci. 47:719. Sidel, J. L., H. Stone, and J. Bloomquist. 1981. Use and misuse of sensory evaluation in research
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and quality control. J. Dairy Sci. 64:2296. Warwick, D. P., and C. A. Lininger. 1975. The sample survey: theory and practice. McGraw-Hill, Inc. New York, NY.
Journal of Dairy Science Vol. 66, No. 3, 1983