Duane W. Greene

Preharvest Drop Control and Maturity of ‘Delicious’ Apples as Affected by Aminoethoxyvinylglycine (AVG)

Abstract Aminoethoxyvinylglycine (AVG) applied 2–8 weeks before anticipated harvest significantly reduced preharvest drop of ‘Delicious’ apples. AVG did not affect fruit weight, and it lowered soluble solids slightly in only one of two years. AVG can be considered a legitimate replacement for daminozide for commercial use on ‘Delicious’ apples. AVG and daminozide were comparable in reducing preharvest drop and delaying ripening. AVGappeared to reduce watercore development more than daminozide, while daminozide was more effective at retarding flesh firmness loss on the tree.

Varietal influences on antihyperglycemia properties of freshly harvested apples using in vitro assay models.

The well-known health benefits of apples have been attributed in part to the presence of polyphenols and related antioxidant capacity. The consumption of apples could provide health benefits by reducing the risk for chronic diseases such as metabolic syndrome disease, including type 2 diabetes. Thus, the objective of this study was to investigate the phenolic-linked antihyperglycemia bioactive factors in aqueous and 12% ethanol extracts of peel and pulp from 10 different freshly harvested apple varieties commonly consumed in the United States. The extracts were analyzed for total soluble phenolics, 2,2-diphenyl-1-picrylhydrazyl-linked antioxidant activity, and their associated in vitro α-glucosidase and α-amylase inhibitory activities. In general, peel extracts had higher total soluble phenolic content and related antioxidant capacity than pulp extracts. Quercetin derivatives, protocatechuic acid, chlorogenic acid, and p-coumaric acid were detected, and the amount varied significantly between aqueous and ethanolic extracts. Honeycrisp and Red Delicious varieties had the highest total phenolic contents and a significant correlation with antioxidant capacity (r = 0.91). In addition, high α-amylase and α-glucosidase inhibitory activities in aqueous pulp extracts were found. However, the peel extracts had the highest α-glucosidase inhibitory activity along with low α-amylase inhibitory activity. No correlation between α-amylase inhibitory activity and total phenolic content was observed. However, positive correlations between α-glucosidase inhibitory activity and total phenolics in aqueous (r = 0.50) and ethanolic (r = 0.70) extracts were observed. This study provides the biochemical rationale for animal and clinical studies to determine the suitable varieties with optimum bioactive factors with antihyperglycemia potential.

Phenolic Bioactive Modulation by Lactobacillus acidophilus Mediated Fermentation of Cherry Extracts for Anti-Diabetic Functionality, Helicobacter pylori inhibition and Probiotic Bifidobacterium longum Stimulation

Cherry juice from one cultivar was fermented for 0, 24, 48, and 72 h using Lactobacillus acidophilus, and its effects related to management of hyperglycemia, hypertension, inhibition of Helicobacter pylori, and proliferation of probiotic Bifidobacterium longum were evaluated using in vitro models. Cherry extract was fermented by initially adjusting the pH to 6.0 and at the natural acidic pH. Analysis was carried out by adjusting the pH and at fermented acidic pH at each time point from each of the two samples. Total soluble phenolics decreased over a period of 72 h for initial pH adjusted samples whereas it increased or remained constant for natural acidic pH samples. DPPH linked antioxidant activity and α-glucosidase inhibitory activity decreased for samples where final pH was adjusted whereas it increased for natural acidic pH samples. Fermentation led to a decrease in hypertension-relevant ACE inhibitory activity for all samples. Natural acidic pH samples had Helicobacter pylori inhibitory activity at 24, 48 and 72 h. Based on the rationale that simple phenolics in cherry could behave as proline analogs, the potential recovery of the pathogen from inhibition was evaluated with of addition of 0.5 mM proline in the medium. A proline induced growth recovery was observed indicating that the mechanism of inhibition is related to proline dehydrogenase based oxidative phosphorylation. Overall, no inhibition was observed when samples that had H. pylori inhibitory activity were further evaluated for their effect on probiotic Bifidobacterium longum.

Prediction of Initial Set and the Thinning Response to Postbloom Chemical Thinners on Apples

Experiments were initiated to identify how and when a reasonably accurate assessment of initial fruit retention could be made and to identify a measurement method to allow early assessment of thinner efficacy. An estimate of initial fruit retention could be made when fruit enters the exponential growth stage, which is generally 6 to 9 days after petal fall and the receptacle has expanded to approximately 6 mm. There was a very good correlation between the slowing of fruit growth 4 to 7 days after thinner application and final fruit set, which led to the conclusion that following fruit growth during this critical time was a good and viable method to predict and quantify thinner response.

Development of 6-Benzyladenine as an Apple Thinner

D. W. Greene*, A. Crovetti and R. Menendez University of Massachusetts, Amherst, MA, Abbott laboratories, North Chicago, IL(retired), Valent BioSciences, Long Grove, IL(retired) The road from discovery through evaluation, field testing, and then marketing of 6-benzyladenine (6-BA) is one of the most interesting and longest of the presently-used chemical thinners. In the 1960s 6BA was identified as having high cytokinin activity. Its ability to stimulate cell division in the calyx end of apples resulted in developing a commercial product to elongate apples that also contained GA4+7. Abscission is not a physiological characteristic that is normally attributed to cytokinins but it was soon discovered that this product (Promalin®)could cause some fruit thinning. Initially it was assumed that the thinning was due to the GA4+7 component but 6-BA was also shown to cause abscission. Over the next few years 6-BA was shown to thin apples, increase fruit size and enhance return bloom. The first 6-BA product to be released contained a small amount of GA4+7 and it was not accepted commercially. Not until several years later when an all 6-BA product was introduced that is was accepted and adopted by the apple industry.