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Chengyan Yue and Cindy Tong

We used choice experiments to investigate consumers’ preferences and willingness to pay (WTP) for various apple (Malus ×domestica) varieties. The experiments also asked consumers to evaluate a series of quality attributes by allowing them to taste apples. The choice experiments were conducted in real markets where consumers were making fruit purchases to eliminate any decontextualized biases. The objectives of this study were to determine how much consumers are willing to pay for 13 new and existing apple varieties and learn what quality attributes consumers’ like or dislike in new vs. older apple varieties. Results show that compared with other apple varieties, participants were willing to pay the highest prices for ‘SweeTango®’, followed by ‘Zestar!™’ and ‘Honeycrisp’. Frequent and infrequent buyers were willing to pay significantly different amounts for most of the studied varieties. In addition to WTP estimates, our study also shows what quality attributes consumers consider as improvements compared with existing varieties. Combined with objective measures of these quality attributes, our transdisciplinary study will help apple breeders make more targeted breeding decisions by better understanding what quality attributes consumers like or dislike about the studied varieties.

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Daniel Keifenheim and Cindy Tong*

Anthocyanins are a class of flavonoids that are responsible for pigments in flowers, fruit, and potato periderm. Developing `Norland' potatoes synthesize anthocyanins in periderm tissue when the tubers are mere swollen stolon tips. As the tubers enlarge, anthocyanin accumulation seems to stop, and anthocyanins synthesized early in development seem to be diluted as the tubers enlarge. Expression of dihydroflavonol reductase (DFR) limits anthocyanin synthesis in grape and maize fruit, and in petunia and snapdragon flowers. However, DFR expression in periderm tissue occurred throughout tuber development (Hung et al., 1999). To determine if expression of late anthocyanin pathway genes limit anthocyanin synthesis in developing potato tubers, we performed RNA gel blot analyses. Expression of leucoanthocyanidin dioxygenase and UDP glucose: flavonoid 3-O-glucosyl transferase was observed in swollen stolon tips but not in periderm of later tuber development stages. Surprisingly, expression was also observed in cortex tissue, although that tissue remained white throughout tuber growth.

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Chengyan Yue and Cindy Tong

Determining consumers' preferences and willingness to pay (WTP) for organically grown and locally grown fresh produce is very important for stakeholders because it helps them figure out what type of fresh produce to grow and sell, what to emphasize in marketing efforts, and what are reasonable prices to charge. However, the literature that studies and compares consumers' preference and WTP for both organically and locally grown fresh produce is sparse. The objective of this study was to investigate consumers' WTP for organically grown and locally grown fresh produce and the marketing segmentation of these two types of produce. We combined a hypothetical experiment and nonhypothetical choice mechanism to investigate consumers' WTP for the attributes organic, local, and organic plus local for fresh produce. We found that when real products were used in the hypothetical experiment, the hypothetical bias (the difference between what people say they will pay and what they would actually pay) was not high. We found that consumers' WTP for the organic attribute was about the same as their WTP for the local attribute. Consumers' sociodemographics affected their choice between organically grown and locally grown produce. Furthermore, we found that consumers patronized different retail venues to purchase fresh produce with different attributes. The findings of the research have great importance for fresh produce stakeholders to make correct production and marketing decisions; the findings also contribute to experimental method choice in consumers' WTP research.

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Gene E. Lester and Cindy B.S. Tong

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Annalisa Hultberg, Michele Schermann, and Cindy Tong

To learn what areas should be emphasized in future educational good agricultural practices (GAPs) training efforts, a survey on usage of GAPs was mailed to 855 vegetable growers in Minnesota. We received a 32% response rate and a 43% cooperation rate. Over 65% of respondents reported compliance to proper worker hygiene practices, harvest container and tool sanitization and cleaning, water treatment to reduce the potential for microbial contamination, and protection of growing and stored vegetables from contamination. Small acreages and a diverse array of vegetables are typical characteristics of the majority of Minnesota vegetable farms. Seventy-seven percent of respondents farmed 15 acres or less. Most farms grew 10 or more different vegetable crops, and farmers markets, u-pick operations, and roadside stands were the most common marketing outlets. Overall responses to this study indicated that farmers currently believe they adhere to many recommended food safety best practices, but are lagging in key areas such as treating wash and processing water, taking measures to keep animals out of production fields, and cleaning and disinfecting harvesting tools and containers on a scheduled basis.

Open access

Renae Moran, Jennifer DeEll, and Cindy B.S. Tong

We evaluated regional variation in the Delta Absorbance Meter® index of absorbance difference (IAD) as a measure of harvest maturity and for predicting the occurrence of storage disorders in ‘McIntosh’ apples [Malus ×sylvestris (L.) var. domestica (Borkh.) Mansf.] in 2016 and ‘Honeycrisp’ apples in 2016 and 2017. Apples were grown in Maine (ME), Minnesota (MN), and Ontario (ON), and they were harvested from one orchard in each region, and two to three times each year, followed by cold storage at 0.5 °C for 2 months in 2016 and 4 months in 2017. In 2016, ‘Honeycrisp’ IAD values were similar in ME and ON, but lower than in MN. In 2017, IAD was greater in ME than in the other two regions during the first harvest, and it similar to MN in the latter two harvests and lower in ON than in the other regions. In ‘Honeycrisp’ apples, IAD was more strongly related to starch pattern index (SPI), internal ethylene concentration, and fruit peel blush than to chlorophyll or soluble solids concentration. Soft scald incidence (SSI) of ‘Honeycrisp’ fruit was greater in ME than in MN and ON in both years. In ME, SSI was related to IAD at harvest in both years, but with an inverse relationship with the first harvest and a positive relationship in the second harvest. A positive relationship also occurred in ON in 2017. SSI was not related to IAD at harvest in MN in both years and ON in 2016. Regional similarities in patterns of change in ‘Honeycrisp’ fruit IAD were not consistent from year to year, and this indicates that a single IAD standard should not be used to assess fruit maturity in different regions. In ‘McIntosh’, IAD values were variable among the three regions and were not related to other maturity indicators. IAD was not useful for measuring maturity in ‘McIntosh’ apples, but it was weakly related to core browning incidence.

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Harpartap Mann, David Bedford, James Luby, Zata Vickers, and Cindy Tong

During storage, many apple (Malus ×domestica Borkh.) genotypes lose their desirable textural qualities, but some like `Honeycrisp', maintain their sensory Crispness and Firmness. To understand this differential response of genotypes to postharvest changes in texture, reliable and quantifiable methods of texture measurement are needed. This study integrated data from a snapping test, confocal laser scanning microscopy (CLSM), and sensory panels to study postharvest textural changes and to predict sensory textural attributes of Firmness, Crispness, Mealiness, and Juiciness. Three separate analyses on fresh, stored, and combined fresh and stored fruit data yielded different predictors for the same sensory attributes. Change in Crispness during storage was successfully predicted by change in Work during storage. Cell number and size were related to fresh fruit texture and its maintenance during storage. Unique textural properties of `Honeycrisp' were found to be inherited by its progeny.

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Ann Marie Connor, James J. Luby, and Cindy B.S. Tong

Narrow-sense heritability and among-family and within-family variance components were estimated for antioxidant activity (AA), total phenolic content (TPH), and anthocyanin content (ACY) in blueberry (Vaccinium L. sp.) fruit. AA, TPH, and ACY were determined in the parents and in 10 offspring from each of 20 random crosses for each of 2 years at Becker, Minn. Offspring-midparent regression analysis provided combined-year heritability estimates of 0.43 ± 0.09 (P ≤ 0.0001) for AA, 0.46 ± 0.11 (P ≤ 0.0001) for TPH, and 0.56 ± 0.10 (P ≤ 0.0001) for ACY. Analyses of variance delineated variation among and within families for AA, TPH, and ACY (P ≤ 0.001). Year-to-year variation in the means for all offspring genotypes was not significant for AA or TPH, but there were changes in rank between years for families and for offspring within families for these traits. Year-to-year variation in the mean for all offspring genotypes was significant for ACY, but rank changes were observed only among offspring within families, not among families. In total, 18 of 200 offspring from 7 of the 20 crosses were transgressive segregants for AA, exceeding the higher parent of the cross by at least two sds. Estimates of variance components showed that variation among families accounted for 24% to 27% of total variance for the three traits. However, variation within families was greater than that among families, accounting for 38% to 56% of total variance for the three traits. These results suggest that increasing antioxidant activity in blueberry through breeding is feasible, and that the breeding strategies utilized should exploit the large within-family variation that exists.

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Ann Marie Connor, James J. Luby, and Cindy B.S. Tong

Variation in antioxidant activity (AA), total phenolic content (TPH), and total anthocyanin content (ACY) was examined in 1998 and 1999 in fruit of 52 (49 blue-fruited and 3 pink-fruited) genotypes from a blueberry breeding population. The species ancestry included Vaccinium corymbosum L. (northern highbush blueberry), V. angustifolium Ait. (lowbush blueberry), V. constablaei Gray (mountain highbush blueberry), V. ashei Reade (rabbiteye blueberry), and V. myrtilloides Michx. (lowbush blueberry). Using a methyl linoleate oxidation assay (MeLO) on acidified methanolic extracts of the berries, a 5-fold variation was found in AA in 1998 and a 3-fold variation in 1999 among the blue-fruited genotypes. Analyses of variance (ANOVA) revealed variation among genotypes (P < 0.0001) in single and combined years, regardless of inclusion of pink-fruited selections and adjustment for berry size. While mean AA of all genotypes did not change between the 2 years, ranking of some genotypes for AA changed significantly between 1998 and 1999. Of the 10 genotypes that demonstrated the highest AA in 1998, four were among the 10 genotypes that demonstrated highest AA in 1999. Similarly, of the 15 genotypes with the highest AA, 10 were the same both years. As with AA, mean TPH of all genotypes did not change between years and ANOVA demonstrated genotypic variation regardless of adjustment for berry size/weight or exclusion of pink-fruited selections. Changes in genotype rank occurred between years. The difference in TPH between lowest- and highest-ranking blue-fruited genotypes was ≈2.6-fold in both 1998 and 1999. Seven of the 10 highest-ranking genotypes were the same both years and TPH correlated with AA (r = 0.92, P < 0.01) on a genotype mean basis for combined years. ACY correlated less well with AA (r = 0.73, P < 0.01 for combined years). When genotypes were categorized into six groups according to species ancestry, V. myrtilloides and V. constablaei × V. ashei crosses ranked highest and second highest, respectively, for AA in both years. The groups comprised of V. corymbosum genotypes, V. angustifolium genotypes, and those with both V. corymbosum and V. angustifolium in their lineage were indistinguishable from each other. Samples from some of the genotypes were analyzed for oxygen radical absorbance capacity and ferric-reducing antioxidant power, and these aqueous-based antioxidant assays correlated well with the lipid emulsion-based MeLO (all r ≥ 0.90, P < 0.01). The three antioxidant assays may be equally useful for screening in a blueberry breeding program and the choice of assay may depend on the goal of the program and the resources available.

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Chen-Yi Hung, Cindy B.S. Tong, and John R. Murray

The color of red potatoes is due to an accumulation of anthocyanins in periderm tissues. The objective of this study was to examine the effect of several factors on tuber redness. Using the red tuber-producing S. tuberosum ssp. tuberosum cultivar Norland, we observed that chroma (intensity of redness) and anthocyanin content of greenhouse-grown tubers decreased as tuber weight increased. There was a slight or no increase in hue (tint). We used HPLC to determine that pelargonidin and peonidin are the major anthocyanidins (aglycones of anthocyanins) in tuber periderm. The ratio of pelargonidin to peonidin increased as tuber weight increased up to 25 g fresh weight. The decrease in chroma was not due to an increase in cell sap pH; we observed a decrease in cellular pH as tuber weight increased. Controlled-atmosphere storage had no effect on tuber chroma or anthocyanin content compared to air storage. Methyl jasmonate, sucrose, or light treatment did not increase anthocyanin accumulation. Tubers exposed to light had less anthocyanin than those kept in the dark. We are examining the developmental expression of anthocyanin biosynthetic genes, as well as the effect of maize transcription factors on anthocyanin synthesis, in tuber periderm.