8:30 am Recent Trends Suggest Optimism for the Sweetpotato Processing Industry.
(72) Kimber, John, North Carolina Sweet Potato Commission Foundation, Benson, NC.
Growing consumer interest in and consumption of sweet potatoes during the past 10 years has created a ramp-up in year round usage,
new products within the food service and retail sectors, expanding processor capabilities, increases in acreage devoted to production,
increases in farm revenue, and increases in farm sector employment. Relatively modest increases in per capita consumption (USDA data)
(2009 3.7 pounds per person versus 2009 5.3 pounds per person) have had a significant impact upon the sweet potato growing industry
(61% increase in tonnage produced, a 62% increase in farm value, and an 18% increase in acreage). No region has been more beneficially
impacted than North Carolina which since 1999 has witnessed a 62% in acreage and since 2006 has experienced a 49% increase in farm
value for sweet potatoes while all other states have realized a 30% increase. North Carolina's good fortune has not been attained
accidentally. Today's presentation will briefly discuss the methods and successes at strategy development begun nearly a decade ago,
the historic but critical linkage to tobacco production, and the early strategy implementation steps. Recent market trends (i.e.
significant growth of sweet potato fry/chip processing and sales, etc) will be presented coupled with insights into the future and
mpediments to long term success, including transitioning from a fresh market focus to include a processed the expansion of processing
dedicated to value added sweet potato products. Key challenges and/or i product focus, managing costs, weevil management, etc., will
be reviewed with a focus upon the current planned activities. The presentation will conclude with a period for questions and discussion
followed by four sweet potato technical presentations by representatives of NCSU and USDA.
9:00 am Sweetpotato Breeding and Genetics: Challenges in Developing Processing Varieties.
(73) Pecota, Ken, G.C. Yencho, and J.E. Driscoll. North Carolina State Univ., Raleigh, NC.
Sweetpotato breeding has mainly been focused on the primary market for sweetpotatoes, fresh market, with new cultivars being tested
for suitability for canning. With the emergence of fries as a potential significant part of the market share, breeding programs are
beginning to focus on traits that produce a better fry product. While many of the traits are the same as for the fresh market,
yield and disease resistance for example, some are completely new. Little attention has been focused on the sugar profiles of raw
sweetpotatoes since consumer quality is assessed on cooked product where native amylases have considerable influence over sweetness.
The high temperatures and shorter cooking requirements of fries and chips leaves little time for the development of sugars, so raw
sugars are of greater import. The quantity and distribution of reducing and non-reducing sugars is critical to control browning and
affects consumer preference scores in taste trials. Adding traits to a breeding objective increases the amount of material to be
screened to achieve the goal. However there are traits such as skin smoothness, skin color and lenticel prominence that can be
relaxed if a cultivar was to be grown specifically for processing. An overview of the breeding methods used in sweetpotato breeding
will be presented and related to the shift in importance of traits from tablestock to fry processing.
9:30 am Key Sweetpotato Cultural Management Practices and Production Efficiencies to Consider for the Processing Industry.
(74) Schultheis, Jonathan, D.W. Monks, K.M. Jennings, M. Abney and Z. Pesic-VanEsbroeck.
North Carolina State University, Raleigh, NC.
Economically, sweetpotato (SP) is the most important vegetable crop grown in North Carolina (NC) and valued at $170 million in 2009.
NC is the leading state producer of SP accounting for 47% of the crop sold in the U.S.; its climate and infrastructure is well
suited for the production of this tropical crop. The primary focus of the SP industry is the fresh market. Key processors have had
double digit growth in SP fry sales the last 5 years, thus the processing market has received increased attention. The
Micropropagation Unit and Repository at NC State University was established in 1996 - it is a model program and insures that only
the highest quality SP propagules are reproduced annually and distributed to the industry. Much hand labor is required to produce
SP, a substantial cost being plant establishment. To reduce plant establishment costs, we are searching for genetic material and
production practices that will produce high yields and quality roots using cut seed pieces. Unlike white potato which uses the
tuber for planting, SP roots currently cannot be used as a propagule. Other areas of production importance and research focus
are soil moisture and irrigation, planting considerations, and pest management. Key elements in each area will be reviewed. Harvest
in NC is mainly by hand and is the other high cost component related to SP production. The crop must be handled with care as the
skin of the SP is easily damaged during harvest. Since the crop is primarily sold for fresh market, the cosmetic condition of the
root is very important. Mechanical harvest of the SP crop will be an important means in which to reduce production costs. A shift
in paradigm is necessary to best meet the needs of the SP processing industry.
10:00 am Break
10:30 am Recent Refinements in Horizontal Ventilation Sweetpotato Storage
(75) Boyette, Mike. Department of Biological and Agricultural Engineering, North Carolina
State University, Raleigh, NC.
In the last twenty years, approximately 15 million bushels of on-farm sweetpotato storage has been built in North Carolina utilizing
horizontal ventilation. Horizontal ventilation facilities have also been widely built in other sweetpotato producing states as well
as a number of foreign countries. Through cooperation between growers, building contractors, equipment supplier and university
researchers, much has been learned that has allowed us to refine the systems that are being presently built in many beneficial ways.
Compared to buildings built in the early 1990s, the latest built sweetpotato facilities are larger, more economical, more energy
efficient and give a much higher level of environmental control than a few years ago. For example, the incorporation of booster fans
has allowed room length to increase to 120 feet or more. The use of supervisory control and data acquisition (SCADA) systems now are
widely used to monitor and control room conditions with very little effort. By utilizing variable frequency drives (VFD) on the fan
motors, facilities can be more precisely controlled while saving a significant amount of electrical costs. We have also learned to
optimally operate these facilities despite variations in harvest conditions or seasonal changes in weather throughout the 10 plus
months the sweetpotatoes can be held in storage.
11:00 am Biochemical changes in sweetpotatoes during storage and implications for processing of value-added products
(76) Truong, Den. USDA-ARS Food Science Research Unit, Department of Food, Bioprocessing
and Nutrition Sciences, North Carolina State University, Raleigh, NC.
Consumer demand for processed foods from carotene-rich sweetpotatoes (SP) especially SP French fries, chips and puree-based products
has increased in recent years in the United States. However, variation in root quality among the cultivars during long-term storage
remains a challenge in large-scale production of these thermally processed products. For commercial success, the products should be
of consistent quality regardless of root storage duration. At harvest, the commercial SP cultivars contain 18-22% dry matter, 10-13%
starch, 0.2-1.2% reducing sugars (glucose, fructose) and 2-3% sucrose. After 1 week of curing at 30¡C and 85-90% relative humidity
(RH) as commonly practiced for fresh SP markets, reducing sugars increased by 2-6 folds while sucrose slightly increased by 1.2-1.5
folds. These sugars had sharp increases up to 6 weeks in storage at 13-15¡F, 85-90% RH then followed by incremental increases until
48 weeks. The levels of dry matter, starch and beta-amylase activities decreased while alpha-amylase activities increased during
long-term storage. The higher concentrations of reducing sugars are often associated with more browning and acrylamide formation in
processed products. On the other hand, high levels of sucrose, starch and amylase activities can have beneficial effects on sweetness
and textural properties of SP fries and purees. Therefore, selection of genotypes with low reducing sugars (< 0.2%), high sucrose
content coupled with appropriate postharvest handling practices and processing techniques should be considered as an integrated
approach to provide SP with suitable quality for the food processing industry.
11:30 am Discussion
Jonathan Schultheis
