consumer acceptance of provitamin a-biofortified maize in maputo, mozambique

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Food Policy 33 (2008) 341–351

Consumer acceptance of provitamin A-biofortified maizein Maputo, Mozambique

Robyn Stevens, Alex Winter-Nelson *

Department of Agricultural and Consumer Economics, University of Illinois at Urbana–Champaign, 1301 West Gregory Drive,

Urbana, IL 61801, United States

Received 8 August 2007; received in revised form 29 October 2007; accepted 21 December 2007

Abstract

Biofortified staple foods hold the potential to alleviate micronutrient malnutrition in many impoverished regions of the world. How-ever, biofortification often alters the flavor, appearance, and other features of foods in ways that may limit consumer acceptance of thenew varieties and diminish their impact. This research examined the acceptance of provitamin A-biofortified maize through taste testsand a trading experiment conducted in Maputo, Mozambique. On average, participants ranked the taste, texture, and appearance oftheir local white maize over an orange, biofortified variety and over a white variety with similar texture and flavor as the biofortifiedmaize. Nonetheless, a large share of participants in a framed experiment accepted offers to trade local white maize meal for meal fromthe biofortified maize. Household size, the presence of small children, dietary diversity, and perceived taste were statistically significantdeterminants of acceptance. Results suggest that existing preferences for white maize do not preclude acceptance of orange, biofortifiedvarieties and that provitamin A-biofortified maize may be a self-targeting nutritional intervention.� 2008 Elsevier Ltd. All rights reserved.

Keywords: Biofortification; Consumer acceptance; Micronutrient malnutrition; Mozambique

Vitamin A deficiency (VAD) adversely affects the healthand life expectancy of some 250 million children under theage of five worldwide (HarvestPlus, 2006). VAD impairseye health and the immune, respiratory, and reproductivesystems. As a result of their weakened immune systems,vitamin A deficient children face increased risk of dyingfrom measles, diarrhea, or malaria. Severe VAD has a60% fatality rate, and even sub-clinical deficiency increasespreschooler mortality by 23% (McGuire, 1993). In Africaalmost 50% of children under five are clinically or sub-clin-ically deficient in vitamin A (FAO/WHO, 1998). Typical ofmany African countries, Mozambique has 2.3 million chil-dren who are vitamin A deficient and VAD contributes to35% of the country’s child deaths (Aguayo et al., 2005).

An appropriate diet is crucial to receiving adequatelevels of vitamin A. Preformed vitamin A is available in

0306-9192/$ - see front matter � 2008 Elsevier Ltd. All rights reserved.

doi:10.1016/j.foodpol.2007.12.003

* Corresponding author. Tel.: +1 217 244 1381.E-mail address: [email protected] (A. Winter-Nelson).

animal products and the human body can synthesize thenutrient from carotenoids found in many fruits and vegeta-bles. Unfortunately, diets typically consumed by the poorin developing countries consist mainly of cereals with littlemeat, fish, fruit or vegetable products. Efforts to alleviateVAD have included provision of dietary supplements,fortification of processed foods, promotion of dietarydiversification, and most recently, biofortification of staplecrops. Through biofortification, staple crops are bred orengineered to have greater concentrations of provitaminA carotenoids or other micronutrients. While biofortifica-tion is promising in many respects, there are questionsabout whether consumers will accept biofortified foodsespecially when biofortification affects the appearance, fla-vor and aroma of the staple. This research uses sensoryperception data and a framed field experiment to examinethe acceptability of biofortified maize in urban Mozam-bique. Using available supplies of biofortified maize, maizethat is nearly isogenic to the biofortified variety but lacks

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342 R. Stevens, A. Winter-Nelson / Food Policy 33 (2008) 341–351

the provitamin A carotenoids, and local maize, the researchassesses consumers’ preferences over maize varieties andthe likely market response to biofortified maize.

Vitamin A biofortification

Biofortification of staple crops promises many benefitsover other approaches to improving micronutrient con-sumption. First, low-income households are implicitly tar-geted, as staple crops are dominant in the diets of people inpoverty. Also, farmers in remote areas who may havelimited access to other interventions can grow the cropsthemselves and store them for continuous consumptionthrough the year (Nestel et al., 2006; Lucca et al., 2006).Thus, households that may not be reached by supplemen-tation campaigns and may not purchase foods that are for-tified can still adopt biofortified crops. In the case ofvitamin A, biofortification has the advantage of eliminat-ing risks of toxicity. Massive doses of supplements orexcess consumption of foods fortified with preformed vita-min A can be toxic, but toxicity is less likely to arise fromconsumption of carotenoids that the body synthesizes intovitamin A (Penniston and Tanumihardjo, 2006).

In addition to improved coverage and reduced risk ofnegative health effects, biofortification also implies lowrecurrent costs compared to other methods. Successfulone-time investment in development of biofortified cropsprovides nutritionally-enhanced varieties for productionand consumption indefinitely. HarvestPlus (2006) estimatesthat US$80 million can provide 7% of the South Asianpopulation with vitamin A supplements (at 25 cents/deliv-ery) and 33% of the population with iron supplements (at10 cents/delivery) for 2 years. Meanwhile the same invest-ment could be used to fund research, development, dissem-ination, and evaluation of six biofortified staple crops to beused throughout the world over an indefinite period.

Biofortification can be achieved either through geneticmodification, as in the case of golden rice, or through con-ventional breeding. The method of development can haveconsiderable impact on the dissemination and acceptanceof a biofortified food. Despite its apparent nutritionalbenefits, golden rice has been very slow to move throughregulatory processes and may face consumer resistancebecause of its GMO status. In contrast, maize and sweetpotato varieties have been biofortified with provitamin Athrough conventional breeding. Regardless of the methodof biofortification, the process may introduce features towhich producers and consumers are unaccustomed. Forinstance, increases in carotenoids result in a change incolor, such as the change from white sweet potatoes ormaize to orange varieties. An aroma is also associated withcarotenoid biofortification.

Households in eastern and southern Africa generallyconsume white maize, which does not contain provitaminA compounds. Market evidence from Mozambique andelsewhere suggests that white maize is preferred over yellowvarieties which have been introduced as food aid (Tschirley

and Santos, 1995). However, Mozambique’s recent successin introducing orange-fleshed sweet potatoes (OFSP) sug-gests that with appropriate education efforts consumersare willing to change consumption habits with respect tofood appearance (Low et al., 2007).

This research uses sensory perception data and an exper-imental exchange process to determine the acceptability ofbiofortified, orange maize to consumers in Maputo,Mozambique and to identify trait and price features thatcould encourage acceptance. While production traits arealso important to successful introduction of a biofortifiedcrop, this research aims to determine whether the likelyconsumer response to orange maize warrants investmentsto develop varieties that are suitable for local production.

Orange maize in Mozambique

White maize is the most common staple crop producedand consumed in Mozambique. In any year, the northernregion accounts for approximately 50% of maize produc-tion and 60% of maize sales, while the South producesand sells very little maize (10% and 2% respectively).Almost all of the maize produced in the country is con-sumed domestically; however, due to poor railways androads, transporting maize from the northern productionareas to the southern region is very expensive. Therefore,maize is imported into the southern cities, including Map-uto where 20% of Mozambique’s population resides. In2002/2003, 70% of rural households in the South werenet purchasers of maize (Tschirley et al., 2006). Rice con-sumption is also substantial and many households in Map-uto rely more heavily on rice than maize as a staple food.

With the support of HarvestPlus, scientists at the Uni-versity of Illinois have recently developed orange maizewith high levels of provitamin A carotenoids (Rocheford,2006). This maize, which has been bred through conven-tional means rather than genetic modification, may repre-sent a way to improve the vitamin A status of deficientindividuals in Mozambique and elsewhere in the develop-ing world. However, the new variety has characteristicsthat differ considerably from those of the maize that is cur-rently consumed. A number of maize characteristics are ofpotential interest to consumers, including the grain color,flavor, aroma and texture. Texture traits of biofortifiedmaize can be altered through breeding, but it is unlikelythat the characteristic color, flavor, and aroma of bioforti-fied orange maize can be removed. Therefore, consumers’reactions to these traits are potential deterrents toacceptance.

Methodology

This study uses a framed field experiment to determinefactors affecting acceptance of provitamin A-biofortifiedmaize and consumers’ willingness-to-pay for the product.In contrast to a contingent value approach, the experimentpresents participants with an opportunity to engage in an

1 Participants generally did not distinguish between ‘‘taste” and ‘‘overallexperience”.

2 Written material explaining the research was available, but respon-dents were not required to read this material and there is little evidence ofits use.

R. Stevens, A. Winter-Nelson / Food Policy 33 (2008) 341–351 343

actual exchange, rather than giving a stated response to ahypothetical question. Thus it avoids the issues of design,cognition and strategic bias that complicate contingentvalue methods (Diamond and Hausman, 1994).

Unlike laboratory experiments in economics, which usu-ally occur in classrooms, this framed field experiment wasconducted in a marketplace, where subjects representedthe population of interest, had experience with food pur-chases and trade, and were in a normal environment formaking market decisions (Harrison et al., 2002; Carpenteret al., 2005). The market setting, however, limited theoptions for using a sophisticated bidding process in theexperiment. The research included a sensory perceptionexercise and continued to a structured trade in which par-ticipants were given the opportunity to exchange whitemaize meal for an amount of the biofortified orangevariety.

Orange and white near-isogenic lines of maize wereshipped to Maputo, Mozambique in the summer of 2006.The near-isogenic white line differs from the biofortifiedvariety only in carotenoid content and associated traits,such as color and aroma. While the biofortified and near-isogenic maize have the same texture, the former is orangeand the later is white. The biofortified maize also has a dis-tinct aroma associated with carotenoids that is absent inthe near-isogenic white variety. Because the supply oforange maize and its isogenic counterpart remain extremelylimited, the experiment was structured to expand the num-ber of participants given the amount of grain available forthe study.

The experiment was conducted from August 15–18,2006. One day before the experiment, local white maizemeal was purchased in the marketplace and the biofortifiedmaize and its near-isogenic (white) counterpart weremilled. The local white maize had been milled with thepericarp removed while the new varieties were milled withpericarp intact. Although urban consumers prefer maizemeal without the pericarp, the orange and white isogenicvarieties were milled with pericarp to ensure that nutrientsremained in the orange maize. Clear, plastic bags werefilled with approximately 0.6 kg of local white maize meal.This volume was chosen to approximate a local unit ofmeasure in the marketplace and to provide an amount thatcould be practically used by the recipient. The value of thisvolume of meal is approximately US$0.20–0.25. InMozambique, where over 75% of citizens live on less than$2 per day and 25% live on less than $1 per day, this valueis large enough to encourage participants to display eco-nomic behavior. Bags were also filled with either 0.3 kgor 0.6 kg of orange maize meal. Maize meal porridge,called xhima, was prepared from each of the three maizevarieties each morning of the experiment. Beef stew wasalso prepared to accompany the xhima.

Market stalls were set up in the Xiquelene marketplaceon two consecutive days, with a different location withinthe market used each day. The following two days, stallswere set up in the Xipamanine marketplace in another sec-

tion of Maputo, again with different locations within themarketplace selected each day. Each of the locations wassufficiently removed from the other so that there was littlechance of participants on later days having informationbeyond what was available to participants on earlier days.A market official was present to observe and permit theexperiment to occur each day. The first day was devotedto pre-testing the instrument and refining the experiment.Data from this day are not included in the final analysis.

Upon arrival at the market location, a Mozambicanresearcher made a brief public announcement describingthe nutritional benefits of orange maize, explaining the pur-pose of the experiment, and introducing the procedures tobe followed. Another member of the research group thendemonstrated the experiment, and the experiment pro-ceeded with participants voluntarily approaching the table.After completing a short questionnaire covering demo-graphic and economic variables, participants were given asmall portion of each of the three types of xhima, askedto taste each separately, and then give a score for the taste,texture, appearance, and aroma of each type. Scores weregiven as 1 – very bad, 2 – bad, 3 – okay, 4 – good, 5 – verygood. Participants were also given an opportunity to makeany comments on the xhimas and provide an overall score.1

Since the orange maize was described as nutritionallysuperior, it is possible that respondents ranked the producthighly to signal an interest in nutrition rather than theirsensory perceptions. Given the flow of people in the mar-ketplace and the duration of the experiment (3–4 h eachday), it is likely that many of the participants did not hearthe initial announcement.2 Nonetheless, all participantsrecognized the orange maize as novel and their responsesmay have been influenced by a desire to accommodatethe researchers. Strongly negative responses suggest thatthis was not a universal tendency. While a bias towardsassent may affect sensory perception results, it is much lesslikely to influence behavior in the trading exercise thatfollowed.

After providing sensory perception information, eachparticipant was given a 0.6 kg bag of the local white maizemeal and informed that it was his/hers to keep or trade.The researcher then offered a randomly pre-assignedamount of orange maize meal, between 0.5 and 3 timesthe amount of white meal the participant had been given.The participant was asked if he/she would want to tradethe local white meal for the amount of orange meal offeredand the response was recorded on the survey. The partici-pant was then asked if he/she would be willing to tradehis/her white meal for a bag of tomatoes with a valueequivalent to the white meal, and the response wasrecorded on the survey. In order to obtain a large enough

Table 1Descriptive statistical analysis of data collected days 2–4 (n = 201)

Minimum Maximum Mean Median Std.dev.

Gendera 0 1 0.69 1 0.47Age 14 70 37.85 37 13.21# People in house 1 20 6.69 6 3.20# Children <12 years 0 9 2.21 2 1.74#Children <3 years 0 8 0.72 0 1.08Shops?b 0 1 0.67 1 0.47Cooks?b 0 1 0.41 0 0.49Month – meatc 0 1 0.71 1 0.46Month – eggsc 0 1 0.44 0 0.50Month – xhimac 0 1 0.89 1 0.32Month – sweet

potatoc0 1 0.47 0 0.50

Month – vegetablesc 0 1 0.99 1 0.10Month – fishc 0 1 0.91 1 0.28Week – meatd 0 7 1.18 1 1.49Week – eggsd 0 7 0.92 0 1.70Week – xhimad 0 7 2.91 2 2.53Week – sweet

potatod0 7 1.04 0 1.82

Week – vegetablesd 0 7 4.32 4 2.33Week – fishd 0 7 2.77 2 2.22White local – tastee 1 5 4.12 5 1.13White local –

texturee1 5 4.23 5 1.03

White local –appearancee

1 5 4.56 5 0.86

White local – aromae 1 5 3.68 4 1.21White isogenic –

tastee1 5 3.53 4 1.18

White isogenic –texturee

1 5 3.52 4 1.07

White isogenic –appearancee

1 5 3.18 3 1.02

White isogenic –aromae

1 5 3.53 4 1.09

Orange – tastee 1 5 3.60 4 1.36Orange – texturee 1 5 3.39 3 1.27Orange –

appearancee1 5 3.44 4 1.17

Orange – aromae 1 5 3.95 4 1.31Orange offered 0.5 3 1.38 1.5 0.76Trade for orange?b,f 0 1 0.44 0 0.50Trade for tomato?b,f 0 1 0.02 0 0.15

a 0 = male, 1 = female.b 0 = no, 1 = yes.c 0 = not consumed in previous month, 1 = consumed in previous


sample with the quantity of orange maize meal that wasavailable, a coin was tossed to determine if the trade wouldbe made when the participant indicated that he/she waswilling to trade for the orange meal or tomatoes.3 Uponcompletion of the experiment, participants were given somemeat and broth to eat with their remaining xhima. A totalof 249 people participated in the process including 48 in thepre-testing.

Enumerators also approached shoppers in the marketwho did not participate in the experiment to obtain theirdemographic and socio-economic data. This was done todetermine whether the participants in the experiment wererepresentative of the marketplace as a whole. No statisti-cally significant differences were found between the partic-ipants and non-participants at the marketplace. While thepopulation in the marketplace is unlikely to be representa-tive of the population at large, these individuals are a rele-vant sub-group as they are likely to have influence overpurchasing decisions.

Enumerators collected data on the gender, age, andoccupation of each participant, and also their householdsize and the number of children under the ages of twelveand three residing in the household. Participants indicatedwhether they were responsible for shopping or cooking intheir household on a regular basis. Monthly and weeklyconsumption of selected foods (meat, eggs, fish, xhima,green vegetables, and orange-fleshed sweet potato) werereported. Participants provided sensory perception scoresrating the taste, texture, aroma, and appearance of eachof the xhima varieties they sampled. The quantity of orangemaize meal that was offered and the participant’s willing-ness to trade for that amount were also recorded on thesurvey.

Based on the reported food consumption patterns, avariety of dietary diversity variables were calculated. Die-tary diversity was calculated as the sum of the types of foodconsumed in the past week, excluding the starchy staple,xhima. The maximum value of dietary diversity was five.Dietary diversity of animal products (DDanimal) was cal-culated as the number of times the participant reportedconsuming meat, eggs, or fish in the past week divided bythe maximum available meal times, 21. The DDanimal var-iable can range from zero to one.

month.d # of days in the last week consumed.e 1 = very bad, 2 = bad, 3 = okay, 4 = good, 5 = very good.f n = 186.
Descriptive statistics and sensory perceptions
Over three days, 201 participants were surveyed, ofwhich 69% were women (Table 1). The participants rangedin age from 14–70 years, with a median age of 37 years.Most respondents were employed as market or street ven-dors. Household sizes ranged from 1 to 20 members, withup to eight children under the age of three. The medianhousehold size was 6 members, with two children under12 and none under the age of three. 67% of participants

3 None of the isogenic white maize was available for trading.

did the shopping, while only 41% were responsible forthe cooking in their household. Almost 90% of participantshad consumed xhima within the past month, although anaverage participant consumed it only two or three times aweek. Most participants had consumed meat and fishwithin the past month, while less than half had consumedeggs. The median frequency of meat consumption was onceper week, with fish consumed twice weekly on average.

In Mozambique, a 1% increase in dietary diversity hasbeen associated with a 1% increase in income (Hoddinott

0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7

Number of Days Food Was Eaten in Past Week

Num

ber o

f Par

ticip

ants

Fig. 1. Frequency of participants’ consumption of selected foods (n = 201).

Table 2Distribution of sensory perception ratings

Ratinga

1 2 3 4 5

Local white taste 2.5 8.5 18.0 16.5 54.5Isogenic white taste 7.0 12.5 24.5 33.0 23.0Orange taste 12.5 10.0 18.0 26.0 33.5

Local white texture 2.0 6.0 15.0 22.0 55.0Isogenic white texture 5.0 11.0 30.0 35.0 19.0Orange texture 12.0 8.0 32.0 25.0 23.0

Local white appearance 0.5 3.5 11.0 10.0 75.0Isogenic white appearance 7.5 16.5 31.5 39.5 5.0Organge appearance 9.5 9.0 27.5 36.0 18.0

Local white aroma 4.5 14.5 23.0 24.0 34.0Isogenic white aroma 8.0 5.5 29.0 40.5 17.0Orange aroma 9.0 6.0 14.5 21.0 49.5

a 1 = very bad, 2 = bad, 3 = okay, 4 = good, 5 = very good.

4 Some evidence of the role of the pericarp in affecting sensoryperception emerged from taste tests conducted using xhimas made fromthe two new varieties and local maize milled with the pericarp intact. Inthese tastings, conducted during pretesting, respondents ranked the taste,texture, appearance and aroma of the local maize xhima below both thenew varieties on average.


and Yohannes, 2002). Therefore, data on participants’ die-tary diversity indicate both income and the likelihood thata respondent’s diet lacked adequate vitamin A. Fig. 1 pre-sents the frequency with which participants consumed eachfood. Most participants reported consuming meat, eggs, orfish fewer than two times per week, indicating low levels onincome and vitamin A intake.

When considering the sensory characteristics of thethree xhima varieties, most participants preferred the taste,texture, and appearance of xhima prepared with their localwhite maize over xhimas prepared with the new varieties.The average taste score for the orange xhima was not muchlower than that of the local counterpart (3.60 compared to4.12) but the difference is statistically significant(p = 0.000). Many participants did have a favorableresponse to the orange maize xhima, with 33% rating itstaste as very good. However, 55% rated the local xhima

in this way (Table 2). There was a core of about 22% ofparticipants that rated the taste of the biofortified xhima

as bad or very bad. This compared to 11% who rated localxhima in this negatively.

There is a statistically significant difference in meanscore for the texture of the local maize meal xhima (4.23)compared to the orange (3.39) and isogenic white (3.52)varieties. Over half of the respondents rated the local xhima

as very good in texture, but only about 20% rated either theorange or the isogenic white varieties that highly. Thesepreferences regarding texture are consistent with theremoval of the pericarp from the local maize.

Participants rated the appearance of their local xhima

significantly higher than the appearance of either new vari-ety. Men in particular rated the appearance of the orangexhima significantly lower than women, 3.24 for men and

3.53 for women (p = 0.054). Overall, the orange xhima

scored higher for appearance (3.44 on average) than didthe isogenic white xhima (3.18). Negative perceptions ofthe appearance of the isogenic white xhima reflect the mill-ing process, as milling with the pericarp results in a grayertone in the isogenic white xhima compared to the localvariety.4 On average, participants preferred the aroma ofthe orange maize over both white varieties which may

Table 3Comparison of data across days and markets

Day2

Day3

Day4

Xiquelene Xipamanine

White local – tastea 4.00 4.27 4.12 4.00 4.18White local – texturea 4.14 4.18 4.36 4.14 4.27White local –

appearancea4.46 4.52 4.70 4.46 4.60

White local – aromaa 3.70 3.56 3.78 3.70 3.66White isogenic – tastea 3.76 3.19 3.59 3.76 3.41White isogenic –

texturea3.58 3.37 3.57 3.58 3.49

White isogenic –appearancea

3.18 3.03 3.30 3.18 3.18

White isogenic –aromaa

3.67 3.33 3.57 3.67 3.46

Orange – tastea 3.84 2.97 3.93 3.84 3.48Orange – texturea 3.74 2.72 3.62 3.74 3.21Orange – appearancea 3.79 2.86 3.61 3.79 3.26Orange – aromaa 4.15 3.52 4.15 4.15 3.86Age 33.53 40.23 39.41 33.53 39.81# In house 7.05 6.23 6.77 7.05 6.77Week – meatb 0.87 1.55 1.16 0.87 1.34Week – eggsb 0.88 1.05 0.84 0.88 0.94Week – xhimab 3.16 2.38 3.14 3.16 2.78Week – sweet Potato 0.85 0.80 1.44 0.85 1.13Week – vegetablesb 3.94 4.16 4.83 3.94 4.51Week – fishb 2.33 3.24 2.99 2.33 3.11Trade for orange?c 0.51 0.27 0.55 0.51 0.40Sample size 67 64 70 67 134

a 0 = very bad, 1 = bad, 3 = okay, 4 = good, 5 = very good.b # of days in last week consumed.c 0 = no, 1 = yes.

Table 4Acceptance of orange maize flour by trade ratio

Trade ratioa N Acceptance rate

1–2 50 0.361–1 37 0.381.5–1 42 0.482–1 39 0.59*

3–1 18 0.39Total 186 0.44

* Significantly different from 1 to 1 at p = 0.05.a Volume of orange maize meal offered to volume of white.


increase the likelihood of acceptance. The mean score foraroma was 3.95 for orange maize versus 3.68 for localwhite (p = 0.014) and 3.53 for isogenic white (p = 0.000).

Comparing the sensory perception responses for xhima

from the biofortified orange variety and its isogenic coun-terpart reveals no evidence that color is a particularlycritical factor to acceptance (Tables 1 and 2). Since thesetwo varieties differ only by carotenoid content and wereprepared in identical ways, their xhimas have the same tex-ture. The finding of no statistically significant difference inthe average texture scores for the orange and isogenic whitexhimas (3.52, 3.39, p = 0.293) thus provides some valida-tion to the sensory perception exercise. Those participatingin the experiment seem to have accurately perceived thesimilarity in texture.

As the new orange and white maize varieties differ onlyin carotenoid content and not in texture, the effects of theflavor, aroma, and color differences on the perceptions ofthe biofortified product can be identified. On these dimen-sions there is no statistically significant difference in the rat-ings for overall taste experience between the two varieties,while the appearance and aroma of the orange maize arepreferred. Taken together, the sensory perception datayield no evidence of a generally strong aversion to theorange color. Participants preferred the appearance of theirlocal white maize xhima to the orange xhima, but they hadan equally strong or stronger preference for the appearanceof the local xhima over the isogenic white xhima.

Data on the non-participants surveyed in the marketindicated no self-selection bias in the experiment. However,selection bias may have entered the data if informationabout the experiment caused some subsets of the popula-tion to seek out the taste testing sites over time. Table 3presents data for each day of the experiment. There doesnot appear to be any systematic variation in the sampleover time, but differences in location probably had someeffect on the sample. For example, the Xipamanine siteon day three was near a fish market. Thus it is not surpris-ing that fish consumption per week is somewhat higheramong individuals surveyed that day.

The median values of the independent variables indicatethat a typical respondent is a 37 year old woman who livesin a household of six people, two of whom are under 12years of age. She does the household shopping but notthe cooking. She consumes xhima two days per week, greenvegetables 4 days per week and animal products (eggs,meat or fish) three days per week. After tasting xhima madefrom orange maize (milled with the pericarp on) and localmaize (milled with the pericarp removed) she expressed aslight preference for the flavor of local maize but considersboth xhimas to have a good taste.

The overall acceptance rate of orange maize meal at alltrade ratios was 44%. The distribution of offers shown inTable 4 reveals that acceptance generally increased withan increase in the amount of orange offered: 36% acceptedtrades at 1 orange to 2 white, 38% at 1–1, 48% at 1.5–1,59% at 2–1, and 39% at 3–1. Only the difference in accep-

tance between rates of 1 to 1 and 2 to 1 is statistically sig-nificant (p = 0.033). The decline in the acceptance rates atthe highest trade ratio (3 to 1) is not statistically significantdue to the small sample at this offer.

Table 5 presents some indication of the factors affectingacceptance of orange maize meal. Men were less likely totrade for the orange maize meal than were women, and reg-ular shoppers are less likely to trade than non-shoppers,but neither of these differences were statistically significant.Acceptance seems to correspond well to the sensory percep-tion data, as those who ranked the taste of orange at 1 or 2(bad or very bad) only accepted the trade 19% of the time,while those who ranked it at 4 or 5 (good or very good)accepted the trade 64% of the time. The difference in thesetwo acceptance rates is statistically significant (p = 0.000).

Table 5Acceptance of orange maize flour by consumer characteristic

Characteristic n Acceptance rate

Male 59 0.39Female 125 0.46Non-shopper 64 0.52Shopper 137 0.40Orange taste 1–2 43 0.19Orange taste 4–5 106 0.64Orange taste > local taste 62 0.73Orange taste < local taste 114 0.25Frequent meat/fish consumer (>4 times/week) 70 0.36Infrequent meat/fish consumer (<4 times/week) 92 0.53


Also, those who ranked the orange taste higher than thelocal white accepted the trade 73% of the time, while thosewho ranked the taste of the orange lower than the localwhite took the trade only 25% of the time. Again, thisdifference was statistically significant (p = 0.000). Finally,acceptance of the orange maize meal was significantlyhigher among infrequent consumers of meat and fish thanamong those who consumed meat and fish frequently (54%versus 37%, p = 0.016).

5 The cause of the negative and significant coefficient on day 3 is amatter of conjecture. The experiment was conducted near stalls sellingfresh and dried fish that day. This may have affected perceived aromas andcould have influenced sample selection as well.

Multivariate analysis and results

The sensory perception data presented above suggestthat many consumers in urban Mozambique would beopen to consuming orange maize meal. A multivariateanalysis is applied below to gain deeper insight into the fac-tors influencing acceptance. Given the categorical nature ofthe variable of interest (acceptance of the offer of orangemaize) and its distribution over the sample, a probit modelis used in this analysis.

The generalized probit model is as follows, where Y is abinary outcome variable, X is a vector of regressors, and Uis the cumulative distribution function of the standard nor-mal distribution:

PrðY ¼ 1jX ¼ xÞ ¼ Uðx0bÞ

In this application, the dependent variable, acceptanceof trade, has a value of 1 if the participant accepted thetrade and 0 if not. Independent variables in the modelinclude gender (0 for male, 1 for female), age (in years),household size, number of children under age 3, if the par-ticipant was the main household shopper (0 if no, 1 if yes),if the participant was the main household cook (0 if no, 1 ifyes), the number of days in the past week the householdconsumed xhima, orange-flesh sweet potato, and green veg-etables, dietary diversity (calculated as the number of timesthe household consumed meat, fish and eggs out of apossible 21 times in the past week), taste score of the localxhima and the biofortified orange xhima (on a scale of 1–5,with 1 as very bad and 5 as very good), and the offer oforange maize meal relative to the amount of white maizemeal provided (0.5, 1, 1.5, 2, or 3 times the amount ofwhite). Acceptance is expected to be positively related to

the taste score for biofortified orange xhima and to theoffer. If children under three or dietary diversity are posi-tively related to acceptance, there is evidence that orangemaize is more acceptable among consumers who are moreat risk for vitamin A deficiency. Other right-hand-side vari-ables are included in the model as controls.

Logarithmic and quadratic functional forms were testedusing a variety of dietary diversity calculations. The loga-rithmic specification resulted in a pseudo R2 of 0.25 andcorrectly classified 72% of observations. The reducedquadratic specification resulted in a pseudo R2 of 0.34and correctly classified 74% of observations. Based onthese specification tests, the reduced quadratic functionalform using dietary diversity relative to animal productswas selected for the estimation (Table 6). The reduced qua-dratic model correctly classifies 30% of the participants asaccepting the trade and 44% are correctly classified asrefusing the trade. Approximately 26% of observationsare incorrectly classified by the model: 13% incorrectly clas-sified as accepting the trade and 13% incorrectly classifiedas refusing the trade.

As many of the participants did not frequently consumexhima, an additional model was specified to examine if theresults changed when looking at frequent (two or moretimes per week) versus infrequent (less than two times perweek) xhima consumers. Table 6 shows that there are nodifferences between the initial model using xhima consump-tion per week and the model using a dummy variable tocompare frequent and infrequent xhima consumers.

From the reduced quadratic specification, the significantvariables in predicting acceptance of biofortified orangemaize include the number of children under the age ofthree, shopping, frequency of vegetable consumption, die-tary diversity in animal products, and the orange tastescore.5 The coefficient on the linear value of the orangemaize taste score is large and negative (�1.25), while thequadratic coefficient is small and positive (0.27). Thesecoefficients result in a positive effect on acceptance whenthe orange taste score is 5, a negative effect on acceptancewhen the orange taste score is 3 or less, and an approxi-mately neutral effect on acceptance when the score is 4.

Raising the offer (lowering the effective price of orangemaize meal) has the expected result of increasing the prob-ability of acceptance, but it is only statistically significant inthe fully expanded quadratic specification. Moreover theeffect of the offer (price) is relatively small in any case.The trade in this experiment was designed to be largeenough in value to elicit thoughtful behavior by partici-pants; however, for lower income participants, such a largetrade may also have substantial income effects. A personwith low dietary diversity and low income may be moreinclined to accept a trade that yields more absolute value

Table 6Probit model results

Full quadratic Reduced quadratic Xhima dummy variable Without dietary diversity

Day 2 �0.459 �0.402 �0.407 �0.263�0.152 �0.202 �0.197 �0.364

Day 3 �1.197*** �1.068*** �1.056*** �0.979***

(0.000) (0.001) (0.001) (0.002)Gender 0.296 0.274 0.276 0.334

(0.393) (0.409) (0.404) (0.310)Age �0.025 �0.001 �0.001 0

(0.645) (0.915) (0.927) (0.995)Age squared 0.000

(0.630)Household size �0.217* �0.184 �0.185 �0.149

(0.066) (0.117) (0.112) (0.215)Household size squared 0.010 0.007 0.007 0.005

(0.109) (0.222) (0.213) (0.399)Children < 3 years 0.694** 0.370*** 0.371*** 0.342***

(0.018) (0.006) (0.006) (0.009)Children < 3 years squared �0.123

(0.148)Shops �0.494 �0.514* �0.515* �0.3560

(0.106) (0.081) (0.082) (0.22)Cooks �0.283 �0.246 �0.253 �0.304

(0.337) (0.393) (0.381) (0.285)Xhima/week �0.170 �0.021 �0.028

(0.37) (0.673) (0.552)Xhima/week squared 0.021

(0.414)Xhima eatera �0.071

(0.771)Sweet potato/week 0.014

(0.945)Sweet potato/week squared �0.007 �0.008 �0.008 �0.008

(0.823) (0.386) (0.362) (0.412)Vegetables/week 0.416* 0.405* 0.408* 0.333

(0.076) (0.071) (0.072) (0.139)Vegetables/week squared �0.045 �0.044 �0.044 �0.032

�0.119 �0.110 �0.110 �0.235DD animalb �3.967** �3.830** �3.890**

(0.035) (0.038) (0.036)DD animal squared 4.629** 4.462** 4.577**

(0.035) (0.048) (0.042)Local taste 0.396 0.005 0.008 0.007

(0.566) (0.969) (0.952) (0.957)Local taste squared �0.060

(0.557)Orange taste �1.342*** �1.2489*** �1.245*** �1.179**

(0.005) (0.009) (0.008) (0.012)Orange taste squared 0.283*** 0.275*** 0.274*** 0.267***

(0.000) (0.000) (0.000) (0.000)Offer 0.996* 0.863 0.847 0.904

(0.100) (0.154) (0.158) (0.129)Offer squared �0.252 �0.209 �0.205 �0.219

(0.175) (0.254) (0.260) (0.224)Constant 1.111 0.904 0.886 �0.077

(0.595) (0.525) (0.534) (0.959)R2 0.345 0.336 0.335 0.321

Figures in parentheses are p-values.* = Significant at p < 0.1.

** = Significant at p < 0.05.*** = Significant at p < 0.01.

a Xhima/week < 2 = 0, xhima/week P 2 = 1.b DDanimal =

P(meat/week, eggs/week, fish/week)/21.


(or calories). This implies that some of the effect of pricechanges could be captured within the dietary diversity var-

iable. The last column in Table 6 presents results when thedietary diversity variable is excluded. The significance of the


offer variable does not change upon exclusion of the dietarydiversity variable, confirming a rather small impact of priceon acceptance, at least over this range of relative prices.

Figs. 2 and 3 present estimated probabilities of accept-ing biofortified orange maize based on simulation exercisesconducted using the mean and median values of the inde-pendent variables and the coefficients from the reduced

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

1.000

0 1 2 3

# of times animal produc

Mean Values Median Valu

Fig. 2. Probability of acceptance by frequen

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

1.000

0 1

Number of Chil

Mean Values Median Values Median Values w/o Discou

Fig. 3. Probability of acceptance by numbe

quadratic model shown in Table 6 while varying a singlevariable of interest.

Acceptance of the offer to exchange white maize mealfor orange was significantly greater for people whoreported lower consumption of animal products. Con-sumption of such products can be understood as a proxyfor income as confirmed by evidence in Hoddinott and

4 5 6 7

ts consumed in past week

es Median Values w/o Discount

cy of consumption of animal products.

2 3 4

dren Under Age 3

nt

r of children under age 3 in household.


Yohannes (2002). Additionally, low consumption of ani-mal products may suggest the existence of VAD, as thosewho consume fewer animal products are likely to receiveless vitamin A in their diet. Calculating the elasticity atthe mean values, results suggest that a 10% decline in thefrequency of consumption of animal products is associatedwith a 2% increase in the probability of acceptance. Thissuggests that orange maize could be a self-targeting nutri-tional intervention since those consumers who are morelikely to suffer from VAD are also more likely to acceptthe biofortified food.

Fig. 2 presents the estimated probability of acceptingorange maize at different frequencies of consumption ofanimal products. If these probabilities are calculated usingthe estimated coefficients from the probit analysis and themean values of the independent variables, the resultingprobability of acceptance is based on a price discount of38% for the orange maize. Calculating the probability ofacceptance using median values implies a 50% discounton the orange price. Probabilities of acceptance using themedian values of all variables except the offer and remov-ing the price discount can also be calculated. As the figureindicates, the probability of acceptance is over 70% forthose who consume animal products one time or less perweek regardless of the price discount in this range. Thosewho consume animal products daily, and are thereforeunlikely to be vitamin A deficient, have less than a 50%probability of accepting orange maize unless there is a pricediscount of 50%.

VAD is especially problematic and prevalent amongchildren. Therefore, it is particularly important to deter-mine whether households with children are likely to acceptorange maize. Experience with the orange-fleshed sweetpotato campaign suggests that mothers may be moreinclined to use biofortified foods for their children thanfor themselves or other resident adults. Again, the datasuggest that acceptance is more likely when there are chil-dren in the household (Fig. 3). The probability of accep-tance rises to well over 70% when there are two or morechildren under three years of age in the household.

Simulations concerning relative prices of orange andwhite maize meal suggest a modest impact of discountsand more pronounced effects from premiums on the priceof the biofortified meal. At the mean values, a 10%decrease in the price of orange maize relative to whiteresults in an increase in the probability of acceptance ofabout 1.5% points. For a respondent characterized by themean values of the variables and faced with a 1 to 1exchange, the model suggests a 48% probability of accept-ing the orange maize meal. Based on mean values of con-trol variables, a discount on the order of 25% is requiredto make acceptance likely. There is modest sensitivity tofurther price discounts, but predicted acceptance rates donot exceed 60%, even when orange maize is half the priceof the local maize. Simulations indicate that a price pre-mium on orange maize would significantly reduce accep-tance. The predicted probability of acceptance drops

from 48% to 37% when there is a 50% price premium onthe biofortified product.

Conclusions

These results indicate that orange maize meal is anacceptable product to many consumers in Maputo,Mozambique. The results also suggest that provitaminA-biofortified maize may be a self-targeting nutritionalintervention, as those who are most likely to suffer fromVAD were the most likely to accept the trade for orangemaize meal. These groups include households with youngchildren and households that do not frequently consumeanimal products. Sensory perception data suggest thatbreeding or processing efforts to influence the texture ofbiofortified maize meal could further broaden consumeracceptance. While acceptance would be affected by initialpromotional and educational activities, there is little evi-dence that a substantial price discount would be requiredover the longer term. Priced on par with white maize meal,orange maize could provide low income consumers with anaffordable way to diversify their diets or improve their chil-dren’s nutrition.

These results are subject to some caveats. Provitamin A-biofortified maize is a new product that is visibly differentthan current products in the market. This leads to concernthat the measurement of acceptance may reflect an attrac-tion to novelty rather than true acceptability of the prod-uct. Replication of this study in a variety of settings,perhaps including the same markets, would be helpful indetermining if consumers would consistently purchase bio-fortified maize, or if acceptance was simply due to the nov-elty of the product. Second, the experiment was conductedin an area where maize is not the primary staple for a largeshare of households. In the Maputo area many consumersrely more heavily on rice consumption than on xhima. Thefinding that the frequency of xhima consumption does notaffect acceptance suggests that the results might hold inregions where maize is the dominant staple, but furtherresearch is warranted.

The visible differences between biofortified and conven-tional maize have some negative effect on consumerattitudes towards the cereal. From an institutional perspec-tive this might be a useful attribute rather than a negativefeature. Should an agency choose to subsidize maize forvulnerable groups, using orange grain would reduce thelikelihood of subsidized cereals being diverted into thebroader market. In addition to fostering self-targeting ofat-risk consumers, the color of biofortified maize could alsofacilitate better control and monitoring of targeted foodassistance programs.

Beyond consumer acceptance, biofortified maize canonly reach its full promise if it can be bred with featuresthat are acceptable to producers. The success in establish-ing orange-fleshed sweet potatoes in smallholder produc-tion systems in Mozambique suggests that farmers arewilling to adopt biofortified crops when their agronomic


and consumption traits are appropriate (Low et al., 2007).In addition to further breeding efforts focusing on agro-nomic traits, adoption of biofortified maize will requireeducational initiatives targeting producers and consumersas were used for sweet potatoes, plus the development ofa functional seed distribution system. Breeding efforts tocombine high provitamin A carotenoid content withdesired agronomic traits and related extension initiativeswill require investments that could strain agriculturalresearch budgets in African countries. Unless additionalinternational assistance is secured, investments in bioforti-fied maize breeding will imply reduced funding for otherimportant agricultural research programs.

Finally, impact studies are still needed to determine theeffect of biofortified maize on the health of consumers andon the country’s economy. Such research requires nutri-tional bioavailability studies to assess the amount of vita-min A absorbed by the body, as well as research on thevolume of orange maize that people are likely to consume.Further steps regarding the potential use of biofortifiedmaize will require a multi-disciplinary collaboration anda long term commitment to research on the topic.

Acknowledgments

The authors thank Dr. Torbert Rocheford for providingmaize samples for this research and Dr. Maria Andrade,Constantino Senete and Pedro Chauque of the Institutefor Agronomic Research Mozambique for support andassistance. Financial assistance was provided by the USAgency for International Development and HarvestPlus.

References

Aguayo, V.M., Kahn, S., Ismael, C., Meershoek, S., 2005. Vitamin Adeficiency and child mortality in Mozambique. Public Health Nutri-tion 8 (1), 29–31.

Carpenter, J.P., Harrison, G.W., List, J.A., 2005. Field experiments ineconomics: an introduction. Research in Experimental Economics 10,1–16.

Diamond, P.A., Hausman, J.A., 1994. Contingent valuation: is somenumber better than no number? Journal of Economic Perspectives 8(4), 45–64.

FAO/WHO, 1998. Vitamin and mineral requirements in human nutrition.Report of a joint FAO/WHO expert consultation, Bangkok, Thailand,21–30 September.

Harrison, G.W., Lau, M.I., Williams, M.B., 2002. Estimating individualdiscount rates for Denmark: a field experiment. American EconomicReview 92 (5), 1606–1617.

HarvestPlus, 2006. Micronutrient malnutrition – vitamin A. Availableelectronically at: http://www.harvestplus.org/vita.html.

Hoddinott, J., Yohannes, Y., 2002. Dietary diversity as a household foodsecurity indicator. Food and Nutrition Technical Assistance TechnicalNote No. 4, Washington, D.C.

Low, J., Arimond, M., Osman, N., Cunguara, B., Zano, F., Tschirley, D.,2007. A food-based approach introducing orange-fleshed sweet pota-toes increased vitamin A intake and serum retinol concentrations inyoung children in rural Mozambique. The Journal of Nutrition 137(5), 1320–1327.

Lucca, P., Poletti, S., Sautter, C., 2006. Genetic engineering approaches toenrich rice with iron and vitamin A. Physiologia Plantarum 126 (3),291–303.

McGuire, J., 1993. Addressing micronutrient malnutrition. SCN NewsNo. 9. Administrative Committee on Coordination Sub-Committee onNutrition (ACC/SCN), Geneva, Switzerland.

Nestel, P., Bouis, H.E., Meenakshi, J.V., Pfeiffer, W., 2006. Biofortifica-tion of staple food crops. Journal of Nutrition 136 (4), 1064–1067.

Penniston, K.L., Tanumihardjo, S.A., 2006. The acute and chronic toxiceffects of vitamin A. The American Journal of Clinical Nutrition 83(2), 191–201.

Rocheford, T., 2006, Personal Communication. [email protected],University of Illinois at Urbana-Champaign, Department of CropSciences, 1102 S. Goodwin Ave., Urbana, IL 61801.

Tschirley, D., Santos, A.P., 1995. Who eats yellow maize? Preliminaryresults of a survey of consumer maize preferences in Maputo,Mozambique. Working Paper 53, Department of Agricultural Eco-nomics, Michigan State University, East Lansing.

Tschirley D., Abdula, D., Weber, M.T., 2006. Toward improved maizemarketing and trade policies to promote household food security inCentral and Southern Mozambique. Research Report 60E, Ministry ofAgriculture, Republic of Mozambique.

http://www.harvestplus.org/vita.html

consumer acceptance of provitamin a-biofortified maize in maputo, mozambique

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