Performing Department
Horticulture
Non Technical Summary
Worldwide, and identified as such in this proposal, hard cider is referred to as "cider". Similar to wine and beer, there is a broad range of cider styles, which appeal to a growing group of cider consumers. Recent data suggests that nearly a million Americans drink cider on any given day (Statista, 2016). Many of these new cider consumers previously purchased light beer and are likely to continue purchasing cider now that it is available through most retailers (Petrillo, 2016). Containing between 0.5-8.5% alcohol by volume, cider is made from apples (either culinary cultivars or specialty cider cultivars specifically selected for their juice quality), bulk apple juice, and/or apple juice concentrate. Recent surveys show that cider producers would prefer to make ciders from specialty cider apple cultivars (Peck and Miles, 2015). In order to help sustain this emerging industry, there is a vital need to identify specialized cider apple cultivars that are adaptable to modern orchard production systems and that meet the juice and cider quality expectations of cider producers and consumers.Specialized cider apples contain quality attributes that provide important and noteworthy characteristics to the finished cider. These attributes include bitterness and astringency (naturally provided through a sub-group of polyphenolic compounds called "tannins"), sharpness (naturally provided through organic acids, predominantly malic acid), sweetness (naturally provided through sugars and sugar-alcohols, such as sorbitol), and flavors (naturally provided through volatile aromatic compounds). All apples contain some level of each of these components, but specialty cider apples are unique in that they may contain exceptionally high levels of one or more of these components. For example, some specialty cider apples contain up to ten times higher polyphenol concentrations than culinary apples (Thompson-Witrick et al., 2014; Valois et al., 2006).While there are dozens of European and American specialized cider cultivars that can be used to make cider, many do not perform as well as common culinary apples in commercial orchard situations. Specifically, many cider cultivars are not responsive to chemical fruit thinning, have an extremely biennial bearing habit, tend to be overly vegetative, and/or are highly susceptible to economically important apple diseases. Additionally, apples destined for cider production can be mechanically harvested and pruned and may require lower pesticide inputs than culinary apples because cosmetic defects and even some superficial damage are acceptable for fruit that will be processed soon after harvest. New York State is the second largest producer of culinary apples in the country, but there is currently very little production of the specialized cider apples desired by cider producers. By systematically evaluating a wide range of germplasm and then selecting material that is superior to currently available cultivars, the proposed project will quickly identify the apple cultivars that will become the future of the NY cider industry.
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The goal of the proposed research is to phenotype (i.e., identify and evaluate the horticultural performance and juice quality) Malus xdomestica cultivars, Malus hybrids, and Malus species for desirable characteristics for commercial cider apple production. We will use accessions in the United States Department of Agriculture Plant Genetic Resources Unit (USDA-PGRU) Malus germplasm collection and replicated field plantings located at the Cornell Orchards in Ithaca, NY. Phenotypic data will be used for a complementary genotyping project that is being conducted by Nathan Wojtyna, a graduate student in my lab. Specifically, we aim to identify genetic markers related to cider specific apples, such as those associated with fruit polyphenol and organic acid metabolism. We hypothesize that highly productive apple cultivars with desired cider quality attributes (i.e., high tannin/polyphenol concentration and composition, acidity, juice yield, and consumer sensory preference) and disease resistance can be identified from existing germplasm.Objective 1: Phenotype accession at the USDA-PGRU to identify potential candidates for hard cider production. These extensive collections and breeding populations offer 1,000's of potential genotypes that may have superior horticultural and cider quality characteristics to currently used cider cultivars.Objective 2: Evaluate European cider cultivars that are currently available in the US and offer the fastest route to identifying bitter cider cultivars that are highly productive, adaptable to high-density orchard systems, contribute desired flavors to ciders, and are well suited for NY's climate.Objective 3: Import and test previously unavailable European cider cultivars. Two separate European cider cultivar importations have already occurred (Spain in 2004 and England in 2015). A third importation from France is slated for 2018.
Project Methods
Objective 1: In 2016, MS/PhD student Nathan Wajtyna (funded through other sources) began screening germplasm at the USDA-PGRU collection. Dr. Thomas Chao (the curator for the Malus collection) has been assisting in the selection of potential germplasm to test. In 2016, we tested 30 unique selections. Our goal for 2017-2020 is to phenotype at least 100 additional accessions per year. The accessions selected for phenotyping will be identified by utilizing the Germplasm Resources Information Network (GRIN) database (https://www.ars-grin.gov), which has phenotypic information on 4,867 Malus accessions. Specifically, we identified accessions with high levels of astringency and acidity--two of the most important quality attributes for cider producers. Additionally, we screened out accessions with a soluble solid concentration below 11º Brix (primarily sugars). This was done because low sugar content apples would produce ciders with too low an alcohol content. The final sorting criteria removed apples that were, on average, less than 50 g. This was done to screen out apples that would be too expensive to harvest by hand and too small to be mechanically harvested with existing equipment.Horticultural assessments will include a visual scoring of tree architecture and vigor, root sucker counts, and yield. Starting at budbreak, trees will be assessed once per week until full bloom (that is, when first petals of the king bloom begin to drop). The relative bloom time of each accession will be categorized as early, mid, or late. Bloom density will be rated from 1 to 5 (1 = sparse to no bloom; 2 = light bloom; 3 = moderate bloom; 4 = abundant bloom; and 5 = saturated bloom).Fruit quality assessments will include fruit weight, size, and shape, peel color, juice yield, sugar content (including, sucrose, fructose, glucose, and sorbitol), total acidity and pH, total polyphenol content, individual polyphenol composition, and yeast assimilable nitrogen concentration (important for yeast metabolism during fermentation).Fruit Sampling: Most accessions in the PGRU are single trees. Forty-five apples, selected at random, from each sample tree will be divided into three groups of 15 apples, to allow for three subsamples. Fruit will be selected from upper, lower, exterior, and interior sectors of each tree to reduce within tree variation. Fruit Storage: Fruit will be stored in standard atmosphere cold storage (1-3°C; >90% relative humidity) for no more than seven days. Fruit Maturity: To evaluate maturity, fruit will be sliced equatorially and the starch-iodine index will be determined by dipping the exposed tissue into a potassium iodide solution (1 g potassium iodide plus 0.25 g iodine in 100 mL water), for comparison to staining patterns on published charts (Blanpied and Silsby, 1992). Fruit will be harvested when less than 20% of the flesh is stained with the potassium iodide solution. Internal ethylene concentration will be determined with a gas chromatograph equipped with a flame ion detector (Series II; Hewlett Packard 5890, Wilmington, DE) using a 1 mL gas sample from the apple's core cavity. Flesh firmness will be measured, after removing part of the peel at two locations along the equator of each apple, with a penetrometer (EPT-1; Lake City Technical Products, Inc., Kelowna, BC, Canada) fitted with a cylindrical 11.1 mm diameter tip. Juice Extraction: Apples will be juiced with a Norwalk 280 Juicer (Bentonville, AR). The extraction efficiency will be calculated using the fruit weight and extracted juice weight. Juice Storage: Samples will be stored at -80 °C and then thawed to 4 °C immediately prior to analysis. Juice Analyses: Soluble solids concentration will be measured using a PAL-1 digital refractometer (Atago U.S.A., Inc., Bellevue, WA) and reported as percent Brix. Reducing sugars (fructose, sucrose, and glucose), sorbitol, ammonia, and primary amino nitrogen will be measured on a SpectraMax Plus 384 microplate reader (Molecular Devices, Sunnyside, CA) using packaged kits purchased from Megazyme (Chicago, IL). Titratable acidity will be measured by titrating a 5 mL juice aliquot against a 0.1 N KOH solution to an end-point of pH 8.1 with an 848 Titrino Plus autotitrator (Herisau, CH) and reported as malic acid equivalents. Total polyphenol content will be measured using the Folin-Ciocalteu assay (Thompson-Witrick et al., 2014) and reported as gallic acid equivalents. High performance liquid chromatography will be used to quantify the concentrations of polyphenols, such as: (-) epicatechin, (+) catechin, procyanidin B2, 5'-O-Caffeoyl-quinic acid, caffeoyl-quinnic acid-3, chlorogenic acid, quercetin glycosides, phloetin-2'-O-glucoside, and phloretin-2'-O-xylosyl-glucoside.Based on these data, rapid phenotyping protocols (i.e., a decision-tree and metrics that most quickly distinguish an apple as having a high potential for cider production) will be developed that can be shared with other researchers and industry stakeholders. In years 2 and 3 of this project, we will propagate and begin testing promising selections in field plots.Objective 2: In 2015, a replicated cultivar trial was established at the Cornell Orchards in Ithaca. Cultivars include: Binet Rouge, Brown Snout, Brown's Apple, Dabinett, Ellis Bitter, Harry Master's Jersey, Porter's Perfection, Tremlett's Bitter (Geneva Tremlett's), and Vilberie, each replicated four times in two-tree sets as a completely randomized block design. The trees are planted 3' between trees and 12' between rows and are trained as a tall spindle (a modern, high-density apple orchard system recommended by Cornell Cooperative Extension pomologists and that lends itself to mechanization). Some of the cultivars are starting to bear fruit in 2017. We will keep careful records of material and labor costs, detailing the time it takes to complete each task, so we can calculate the costs of establishment and of production. More thorough economic analyses will also be calculated as the project progresses through subsequent years, as will orchard productivity, which will be measured by tree trunk growth (TCSA), total yields, yield efficiency (yield/TCSA), and fruit size. Fruit and juice data collection and analysis from this trial will be like those listed for Objective 1.Objective 3: In 2004, 25 elite Spanish cultivars were imported into the U.S. These cultivars are officially designated cider cultivars in Asturias, the largest cider producing region in Spain. Relatively few Spanish cider apple cultivars are currently available in the US. Spanish cider (or sidra) tends to be more acidic and acetic than English and French ciders. Spanish cultivars will allow NY producers to explore new cider styles.In 2016, the first nine Spanish cider cultivars (Blanquina, Collaos, Cristalina, Coloradona, Marialena, Piel de Sapo, Raxao, Sangre de Toro, and Solarina) were released from USDA-APHIS quarantine. The extended quarantine period was due to repeated virus detections resulting in the need to propagate the cultivars from tissue culture. The nine cultivars are currently being propagated by Wafler Nursery (Wolcott, NY) and will be put into a similar replicated test planting as described for Objective 2 and we will follow similar procedures as to those outline in Objective 1 and 2. Additional cultivars will be added as they are released from quarantine.The English cultivars include 17 releases from the Long Ashton Research Station known as "The Girls". These cultivars currently account for about 20% of the cider apple acreage in the UK. Until this importation these cider cultivars were unavailable in the U.S. Other UK imports include cultivars that are possibly not true to type, such as Foxwhelp and Tremlett's Bitter. The English cider cultivars will be available for field testing in 2020. Plantings and data collection will be like those outlined in Objective 2.