Thomas W. Walters

Effect of thermal treatments on phytochemicals in conventionally and organically grown berries

BACKGROUND Consumer demand for organic foods is increasing despite a lack of conclusive evidence of nutritional superiority of organically grown produce. The objective of this investigation was to evaluate the effects of thermal treatments on phytochemicals in conventionally and organically grown berries. Two cultivars of conventionally and organically grown red raspberries and blueberries were analysed for total anthocyanins, total and specific phenolic compounds and total antioxidant activity. Fresh berries were thermally processed into cans and juice/puree with and without blanching, and the changes in phytochemicals were monitored. RESULTS Total anthocyanin and phenolic contents of berries were not influenced by the agricultural production system. Total antioxidant activity of berries was also not influenced by the production system, but antioxidant activity varied significantly between cultivars. After canning, total anthocyanins decreased by up to 44%, while phenolic contents and antioxidant activity of both berries generally increased by up to 50 and 53% respectively. The level of changes in phytochemicals during berry puree/juice processing was influenced by blanching and type of berries. CONCLUSION Phenolic contents and antioxidant activities of berries increased while total anthocyanins decreased during canning. Blanching prior to puree/juice processing improved the retention of phytochemicals in blueberries.

Effects of Air and Freeze Drying on Phytochemical Content of Conventional and Organic Berries

U.S. sales of organic products continue to climb due to consumer perception of both environmental and health benefits of organic produce. The objectives of this study were to evaluate the effects of air and freeze drying and blanching treatment prior to air drying on phytochemical content of conventional and organic red raspberries and blueberries. Total anthocyanins and phenolics contents and total antioxidant activity were determined in two cultivars of blueberry (‘Duke’ and ‘Reka’) and in ‘Meeker’ red raspberry harvested under two different techniques (hand and machine). The phytochemical content was determined after subjecting the berries to air and freeze drying with or without blanching pretreatment. In general, no consistent differences were noted between the phytochemical concentrations in fresh conventional and organic berries. The effect of drying on the retention of phytochemicals depended on drying technique, cultivar, and production system (conventional or organic). Blanching prior to air drying significantly increased the effective moisture diffusivity in both berries, thus reducing the drying time. In general, air drying caused significant reductions in anthocyanins, phenolics, and antioxidant activity in both blueberries and raspberries. Compared to air drying, freeze drying improved retention of phytochemicals during processing and in some cases it even increased the concentration of phytochemicals. The application of blanching resulted in enhanced moisture transport, thus reducing the drying time. The blanching treatment prior to air drying increased the retention of phytochemicals in dried berries.

Storage effects on anthocyanins, phenolics and antioxidant activity of thermally processed conventional and organic blueberries

BACKGROUND Consumer demand for products rich in phytochemicals is increasing as a result of greater awareness of their potential health benefits. However, processed products are stored for long-term and the phytochemicals are susceptible to degradation during storage. The objective of this study was to assess the storage effects on phytochemicals in thermally processed blueberries. Thermally processed canned berries and juice/puree were analysed for phytochemicals during their long-term storage. RESULTS The phytochemical retention of thermally processed blueberries during storage was not influenced by production system (conventional versus organic). During 13 months of storage, total anthocyanins, total phenolics and total antioxidant activity in canned blueberry solids decreased by up to 86, 69 and 52% respectively. In canned blueberry syrup, total anthocyanins and total antioxidant activity decreased by up to 68 and 15% respectively, while total phenolic content increased by up to 117%. Similar trends in phytochemical content were observed in juice/puree stored for 4 months. The extent of changes in phytochemicals of thermally processed blueberries during storage was significantly influenced by blanching. CONCLUSION Long-term storage of thermally processed blueberries had varying degrees of influence on degradation of total anthocyanins, total phenolics and total antioxidant activity. Blanching before thermal processing helped to preserve the phytochemicals during storage of blueberries.

Impact and Occurrence of Phytophthora rubi and Pratylenchus penetrans in Commercial Red Raspberry (Rubus ideaus) Fields in Northwestern Washington

Red raspberry (Rubus idaeus) production is a vital component of northwestern Washingtons agriculture. The main objectives of this study were to document the occurrence of soilborne pathogens Phytophthora rubi and Pratylenchus penetrans in early stage production fields, relate this information to soil properties, and better understand the individual and combined effect of P. rubi and P. penetrans on raspberry root health. P. rubi was found at each field and P. penetrans population densities were variable (0 to ∼8000 nematodes/g dry root) across locations. In controlled greenhouse studies, P. rubi was very pathogenic to red raspberry ‘Meeker’ at densities >10 oospore/gram soil and there was no interaction between P. rubi and P. penetrans. P. rubi is endemic to raspberry production in this region, and is an aggressive pathogen on raspberry. However, the chronic damage to roots caused by P. penetrans should not be ignored.

Developments in raspberry production, cultivar releases, and intellectual property rights: a comparative study of British Columbia and Washington State.

The Pacific Northwest (PNW) raspberry industry has undergone substantial structural changes over the last two decades driven by shifts in production and trade and strengthened intellectual property rights to protect cultivars. Since the mid-1980s, Washington raspberry production has increased substantively while British Columbia (BC) production has exhibited a downward decline. Plant breeding in the PNW has been affected by the increased globalization of the raspberry trade and the increased emphasis on plant patents and plant breeders rights to protect cultivars. The increased emphasis on intellectual property rights to protect cultivars is likely to affect the accessibility of germplasm and the transaction costs of procuring planting material from European breeding programs. Raspberry research in BC has concentrated its efforts in developing improved cultivars with little research on the effects of management practices on fruit yields. The development of improved cultivars in the PNW has relied on conventional or classical breeding approaches. With reduced public support for raspberry breeding research in the PNW, breeding programs rely more heavily on support from industry associations. Future prosperity of the PNW raspberry industry would require developing competitive cultivars and promoting intellectual property protection to stimulate market development and the world-wide dissemination of improved cultivars.

Contribution of a Winter Wheat Cover Crop to the Maintenance of Root Lesion Nematode Populations in the Red Raspberry Production System

One of the primary production challenges red raspberry (Rubus idaeus) growers in the Pacific northwestern United States confront is root lesion nematode [RLN (Pratylenchus penetrans)]. In this perennial production system, red raspberry serves as a sustained host for RLN. When a red raspberry planting is slated for removal in the fall, a new red raspberry planting quickly follows in the same field the following spring. The primary crop that occurs in rotation with red raspberry is a winter wheat cover crop to provide soil coverage and protection during the winter. The objectives of this research were to determine if winter wheat (Triticum aestivum) provides a green bridge for RLN in continuous red raspberry production systems and to determine if modified winter cover cropping practices can be used to reduce population densities of RLN before replanting red raspberry. Four trials were established in fields being replanted to red raspberry and the following modified winter cover cropping practices were considered: cover crop planting date (at fumigation or 2 weeks after fumigation), termination date (cover crop kill with herbicide 2 or 6weeks before incorporation comparedwith the industry standard of incorporation immediately before planting), and the additional application of methomyl. ‘Rosalyn’ and ‘Bobtail’ winter wheat planted as cover crops in these trials were demonstrated to be maintenance hosts for RLN (ranging from 10 to 947 RLN/gwinter wheat root across trials) allowing them to be a green bridge for RLN to infect the following red raspberry crop. Altering winter wheat cover crop planting date, termination date with herbicide, or methomyl application did not affect RLN population densities in the subsequent red raspberry crop. Although planting an RLNmaintenance host may be of concern to growers, the advantages of reduced soil erosion and nitrate leaching associated with cover cropping outweigh the perceived risk to the subsequent red raspberry crop.