Tomatoes are among the most popular fresh produce items in grocery stores [1]. Grape tomatoes (Solanum lycopersicon L. var. cerasiform) have gained popularity and market share among consumers due to their flavor, sweetness, potential health benefits, and ease of consumption [2]. In a survey of 389 respondents from throughout the United States, 42% preferred grape tomatoes over plum (36%), cluster (27%), cherry (25%), and yellow slicing tomatoes (4.4%). Only red slicing tomatoes were preferred over grape tomatoes (76%) [3]. Grape tomatoes make easy, low calorie snacks and are rich in vitamins A, B, and C. The red pigment, lycopene, has been linked to lower levels of cancer in people who consume large amounts of cooked or processed tomatoes in their diets [4].

In the late 1990s, grape tomatoes were considered a novelty crop and seed were scarce. A single cultivar, >Santa=, dominated the limited market. As demand grew, seed companies began to develop their own hybrids. Originally imported from Asia, there are now more than 20 grape tomato cultivars commercially-available in the United States [4]. While grape tomatoes= enhanced sweetness and convenient size make it ideal for consumers, its high yields and hearty skin are beneficial for producers. However, grape tomatoes present a number of production challenges that differ from those of large-fruited or even cherry tomatoes. Because of their small size, grape tomatoes are a labor-intensive crop to harvest as it takes more time to pick. Similar to grapes in a vineyard, they form clusters on the vine, but need to be picked individually. They should be harvested when the fruit is light pink to red. Harvest any sooner yields off-flavor fruit and they will not sweeten after harvest. Harvest any later results in poor shelf life.

Consumers have indicated that they are willing to pay a premium price for tomatoes that are full-flavored and meet sensory expectations [5-7]. In response to this growing trend, cultivar evaluations were conducted and followed up with sensory evaluations. Descriptive analysis provides the description of the sensory qualities of food. It pertains to the sensing and describing of both qualitative and quantitative sensory attributes. Qualitative attributes are aroma, flavor, texture and sound. Quantitative attributes reflect the degree of the characteristic and is expressed by a scale value. Highly trained panelists are required for descriptive work. Reference scales are used to ensure consistency between panelists during repeated evaluations [8,9].

The objectives of this research were two-fold: 1) to evaluate yield of several grape tomato cultivars and 2) to ascertain consumer preferences through sensory evaluation.

Plant material and growing conditions

Grape tomato research began at the Mississippi State University, Beaumont Horticultural Unit in Perry County, MS in 2002. Ten cultivars were initially evaluated (data not shown). In the spring of 2003, the evaluation was expanded to include 14 cultivars: >Mini Charm= and Gabrielle= (Twilley Seed Co., Hodges, SC); >St. Nick=,>Jolly Elf= and >Morning Light= (Siegers Seed Co., Holland, MI); >Red Grape,>Sweet Olive and >Chiquita= (Johnny=s Selected Seeds, Winslow, ME); >Grapette=, >Fond Red Mini=, and >Sweet Baby Girl= (Totally Tomatoes, Randolph, MI); >Tami G= (Stokes Seeds, Inc., Buffalo, NY); >Santa= (Holmes Seed Co., Canton, OH); and >Navidad (Clifton Seeds Co., Faison, NC) (Table 1). Five-week-old transplants of each grape tomato cultivar were planted on17 June 2003 at the Beaumont Horticultural Unit in Perry County, MS on McLaurin sandy loam soil. Tomatoes were grown using plasticulture on 24 in beds spaced 6 ft apart at a 2 ft staggered within row spacing. A total of 4 20 ft replications of each cultivar were evaluated with 8 plants per replication (N=480). Pre-plant N was applied at 450 lb/acre 5N-6.5P- 24.9K according to soil test recommendations. Rows were side-dressed with 20 lb N per acre at 60 days after transplanting.

Table 1: Catalog descriptions of 14 grape tomato varieties grown at the Beaumont Horticultural Unit in Perry County, MS.

Tomatoes were staked with 8’ stakes and tied using the Florida weave system. Other cultural practices followed current recommendations for commercial tomato production in Mississippi [10]. Entire plots were harvested. There were a total of 6 harvests beginning on 18 Aug. 2003 and ending on 6 Oct. 2003.

Total yield was determined by total fruit weight of the entire plot. Marketable fruit were fully colored with few or no blemishes. Culls included cracked, damaged, and diseased fruits. Data were analyzed using analysis of variance and means were separated with Duncan=s multiple range test at the 5% level.

Sensory evaluation

Eleven of the 14 varieties of grape tomatoes were sent to Mississippi State University for organoleptic evaluation. ‘Chiquita’, ‘Morning Light’, and ‘Jolly Elf’ were excluded from sensory evaluation due to low marketable yields at the time. An expert panel was conducted evaluating the reactions of 5-6 participants to the grape tomatoes at the Garrison Sensory Evaluation Laboratory. Panelists were at least 18 years of age and were from Mississippi State University, Starkville, Mississippi and surrounding areas. All panelists were instructed to taste and evaluate the attributes of appearance, shape, size, color, gloss-shininess, translucency, stem, stem appearance, aroma, descriptor terms of aroma, general tomato aroma, hand/texture/firmness, mouth/ bite/skin penetration, skin chewability, firmness of flesh, mealiness, juiciness, mushiness, internal pressure in mouth, seed/seed size, flavor, sweetness, sourness, saltiness, umami, overripe flavor, and general tomato flavor. Panelists were also instructed to indicate the order of the tomatoes in which they preferred. Data were analyzed using analysis of variance according to Stone et al. [11]. The grape tomatoes were washed in clear, cold water and then rinsed in the same. They were sanitized in a solution of clear, cold water with 100-ppm chlorine bleach. Samples were finally rinsed in clear, cold water and drained on paper towels. The different varieties of grape tomatoes were handled individually and placed on numbered trays to maintain number codes. The grape tomatoes were administered to the panelists along with water to rinse between samples.

Cultivar comparison

Varieties can be subdivided into 3 groups based on marketable yields (Table 2). The highest yielding varieties were St. Nick (2148.4 kg/ha), Mini Charm (2142.8 kg/ha), Sweet Baby Girl (2135.0 kg/ha), Fond Red Mini (2094.1 kg/ha), and Gabrielle (1895.4 kg/ha). The second best performing varieties included Red Grape, Tami G, and Santa yielding 1543.4, 1501.4, and 1490.2 kg/ha, respectively. The third tier of varieties included Sweet Olive, Navidad, Morning Light, Grapette, and Jolly Elf yielding, 981.0, 948.0, 861.3, 850.6, and 719.8 kg/ha, respectively. However, they did not yield significantly higher than other varieties with the exception of Chiquita, which yielded the least at 382.4 kg/ha.

Table 2: Marketable and cull yields (kg/ha) of 14 grape tomato cultivars grown at the Beaumont Horticultural Unit, Perry County, MS.

‘Mini Charm’ and ‘St. Nick’ both exhibited high marketable weights and low cull weights. While ‘Morning Light’ also had a low cull weight of 135.6 kg/ha, that number represents 15% of the total yield for that variety. ‘Santa’ had the lowest cull yield at 96.2 kg/ha.

Sensory evaluation

Twenty attributes were scored by panelists participating in the sensory evaluation of 11 grape tomato varieties (Mini Charm, Grapette, Fond Red Mini, Santa, Gabrielle, Navidad, Sweet Olive, Red Grape, Tami G, Sweet Baby Girl, and St. Nick) (Table 3). ‘Mini Charm’ was rated highest for 8 attributes including, appearance, gloss/shininess, skin chewability, internal pressure, flavor, sweetness, sourness, and saltiness. ‘Red Grape’ was rated highest for tomato aroma, aroma descriptor, translucency, and tomato flavor. ‘Sweet Baby Girl’ was rated highest for mouth feel/skin penetration, firmness of flesh, and mushiness. ‘Grapette’ and ‘Santa’ each rated highest for 2 attributes: tomato aroma and mealiness for ‘Grapette’ and color and juiciness for ‘Santa’. ‘St. Nick’ was only rated highest for umami. ‘Fond Red Mini’, ‘Gabrielle’, ‘Navidad’, ‘Sweet Olive’, and ‘Tami G’ did not rate highest for any of the attributes evaluated.

Table 3: Attribute rankings of 11 grape tomato varieties on a 15-point hedonic scale.

‘St. Nick’, ‘Mini Charm’, ‘Sweet Baby Girl’, ‘Fond Red Mini’, and ‘Gabrielle’ each performed well in variety trials performed under summer conditions in South Mississippi. The most preferred varieties overall in sensory evaluation were Mini Charm, Grapette, Fond Red Mini, ‘Santa’, and ‘Gabrielle’. Overall sensory evaluation preference was given to ‘Mini Charm’, which was later recommended as a Mississippi Medallion winner. These initial observations indicate that the degree of difference of the eleven varieties of grape tomatoes included in the sensory evaluation is consistent. Nevertheless, the degree of difference within each attribute varies. Further study should be given to the relationship of certain attributes for each variety of grape tomato.

This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch project under accession number MIS-149191 and U.S. Department of Agriculture – Agricultural Research Service Specific Cooperative Agreement 58-6404-0-465.