Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 247-250).

Graduation date: 1951

Graduation date: 1976

Hazelnuts are commonly consumed raw and are valued for their numerous health benefits and antioxidant properties. Increased foodborne illness outbreaks associated with Salmonella and Escherichia coli O157:H7 contamination of tree nuts and peanuts generate a need for improving agricultural sanitation procedures. Food-safe chemical sanitizers have shown promise for reducing pathogenic organisms on fresh produce, but minimal research has been conducted for in-shell nuts. The purpose of this study was to determine the effects of water and three food-safe sanitizers on a) the natural microbial load of postharvest in-shell hazelnuts and b) populations of pathogenic Salmonella (S. enterica subsp. enterica ser. Panama) inoculated and dried onto the surfaces of in-shell hazelnuts. The first phase of the study investigated the effectiveness of water, sodium hypochlorite (NaOCl; 25 ppm, 50 ppm), peroxyacetic acid (PAA; 80 ppm, 120 ppm), and acidified sodium chlorite (ASC; 990 ppm) as sanitizers for use on postharvest in-shell hazelnuts. Treatments were applied to two groups of freshly harvested hazelnut samples to examine their effects on total aerobic microorganism populations during different times of harvest (Group 1 = early season, dry weather; Group 2 = late season, rainy weather). Treatments within each group included hazelnuts that underwent a tap water rinse, a tap water rinse followed by a water spray, and a tap water rinse followed by a chemical spray. Due to excess soil attached to shell surface, hazelnuts harvested later in the season (Group 2) had an initial population mean 2.24 log CFU/hazelnut greater than hazelnuts harvested earlier in the season (Group 1). All treatments, including water, resulted in significant population reductions compared to untreated controls (P���0.05). Rinsing with tap water produced reductions of 0.38 log units in both groups, and additional water spraying resulted in reductions of 0.83 and 0.73 log units in Group 1 and Group 2, respectively. None of the chemical treatments were significantly more effective than the water spray treatment in Group 1; however, several chemical treatments in Group 2 were significantly more effective than water spraying. Tight adherence to shell surfaces during dry weather may have increased the chemical resistance of microorganisms on hazelnuts. Treatment with ASC produced the greatest reduction in Group 1 and Group 2 compared to the control (1.22 and 2.08 log units, respectively) and water spray treatments (0.39 and 1.39 log units, respectively), but the efficacies varied between treatment groups. Wide variation between Group 1 and Group 2 treatment results made determination of chemical efficacy difficult. The second phase of the study analyzed the effectiveness of water, sodium hypochlorite (NaOCl; 25 ppm, 50 ppm), peroxyacetic acid (PAA; 80 ppm, 120 ppm), and acidified sodium chlorite (ASC; 450 ppm, 830 ppm, 1013 ppm) as sanitizers for reducing Salmonella on in-shell hazelnuts. Hazelnut samples were soaked in pure cultures of S. Panama for 24 h, air dried for 66 h, and then sprayed with water and chemical treatments. Surviving S. Panama populations were evaluated using a non-selective medium (tryptic soy agar), followed by a selective overlay (xylose lysine deoxycholate agar) after a 3 h incubation period. Tight adhesion prevented significant population decreases from physical removal by water, which allowed for clear demonstration of chemical effectiveness. All of the chemical treatments significantly reduced the S. Panama population (P���0.05) compare to untreated and water-sprayed samples. The most effective concentrations of ASC, PAA, and NaOCl treatments resulted in mean microbial population reductions of 2.65, 1.46, and 0.66 log units, respectively. Overall, physical removal of excess dirt appeared to have the greatest effect on the microbial population reductions of postharvest in-shell hazelnuts, and adherence to shells during dry weather appeared to increase the chemical resistance of microorganisms. Future sanitation experiments should consider weather and levels of excess soil on hazelnuts as factors in the apparent efficacy of chemical sanitizers. Testing chemical sanitizers against tightly-adhered Salmonella cells provided consistent results with clear demonstration of chemical efficacies. Acidified sodium chlorite at 1013 ppm was significantly more effective at reducing Salmonella populations than other treatments and shows the greatest potential for use as a postharvest sanitation treatment. Thorough rinsing of hazelnuts in clean tap water, followed by spraying with high concentrations of acidified sodium chlorite could help increase the efficacy of current hazelnut processing. / Graduation date: 2013

It has been reported recently that extracts of filbert nuts demonstrate considerable proteolytic activity on a non-fat milk solids substrate. The addition of these extracts to cheddar cheese, in an attempt to enhance the rate of ripening, has been suggested. In these experiments, the extracts of two varieties of filbert nuts, i.e. Du Chilly and Barcelona, were added to cheddar cheese samples at the milling stage of manufacture. The rate of proteolysis, in the cheese samples, was determined quantitatively by the increase in soluble protein content over a three month period. At the termination of these experiments a taste evaluation was performed on all cheese samples. A statistical analysis on the results of the soluble protein analyses showed that the proteolysis in the treated cheese samples was significantly greater than the proteolytic breakdown in the control samples. A defatted extract of Barcelona variety of filbert nuts was the most effective treatment of enhancing the proteolysis in the cheese samples. The results of the taste tests showed that no significant improvement in the flavor of the cheese resulted from the addition of filbert extracts. / Graduation date: 1951

Graduation date: 1955

Graduation date: 1970

Hazelnuts are mostly non-dormant at harvest but develop seed dormancy after a few days of storage. The seeds have been classified as recalcitrant since they cannot be stored for more than one year under ambient conditions. Cryopreservation has not been satisfactory so an alternative protocol is required. To test for recalcitrance, chilled non-dormant seeds (control) were compared with gibberellic acid (GA3) treated seeds during 6 weeks storage at 5°C or at ambient temperature. Control seed moisture content (MC) was 14-15% compared with 20% for GA3 treated seeds. No change in viability was noted until the end of 6 weeks at ambient temperature, when infection proliferated. Reduced germinability, associated with increased leachate conductivity, was noted on all treatments and controls, with ambient temperature storage most harmful for seed viability. This supports classification of hazel seeds as recalcitrant. However, orthodox behaviour could be induced by reducing seed moisture to <6%, showing survival for more than 3 years at -20°C with acceptable germinability and producing healthy seedlings. Pathogen tests show that 6 weeks chilling to break seed dormancy may activate the seeds’ internal protective mechanisms, thereby reducing infection and enabling germination and healthy seedling establishment. The link between seed viability and protection from free radicals and pathogens was examined. Antioxidant activity in hazelnut seed associates (such as endocarp, funiculus and testa) was found to be much higher than in the seed embryo, perhaps indicating that hazel seeds have natural protective mechanisms within the pericarp. Antioxidant activity of seed associates increased during chilling, indicating their role in protecting the seed. Nevertheless, TTC test revealed that seeds acclimatised to ii < 6% MC and stored at 5°C for 45 weeks showed viability loss due to damage of the embryonic axes, probably caused by free radicals. Initial tests to stabilise seed moisture content showed that reduction in seed moisture did not impose dormancy and seed moisture content (MC) stabilisation resulted in > 80% germination but many abnormal seedlings. Dormancy reversibility was tested by treatments T1 (one period at 15°C) and T2 (two periods at 15°C), designed following a consideration of the natural environment. Both resulted in reduced germination, delayed seedling emergence, increased abnormal seedlings, reduced seedling height and decreased internode numbers. To test the role of temperature in reduced seed performance, non-dormant hazelnuts were held at either 5°C or at ambient temperature for up to 6 weeks. Seeds from both sets exhibited high viability, but germinability was significantly decreased in the ambient temperature set, associated with increases in leachate conductivity and infection. Work in this thesis has confirmed that dormancy was broken by chilling, with gradually increasing germination as chilling time was increased. Germination increased with increase in chilling and reduction in infection. No infection was recoreded after 6 weeks chilling. It is most likely that protective agents are produced causing suppression of infection. In these experiments it was observed that not all germinated seeds produced healthy seedlings, suggesting that germination tests without observation of seedlings may give an incomplete assessment of germination success. Assessment using the Tetrazolium test (TTC) was found to be much more dependable and it was also possible to detect damage to specific tissues that might result in unhealthy seedlings.

Viability and dispersal of ascospores of Anisogramma anomala, the cause of eastern filbert blight (EFB) on European hazelnut, from diseased branches pruned from trees were measured. In each of two years, branches bearing stromata of A. anomala were cut in mid-December and compared to branches cut near budbreak in March, when trees became susceptible to infection. The experiment was replicated three times at separated locations. At each location, 125 diseased branches (source) were piled loosely in a 1 x 1 m area. From March to June, spore traps (rain sampling-type) as well as 2-year-old potted hazelnut trees were placed next to each source, 6.4 m upwind and downwind, and 20 m downwind from each source. During seven significant major rain events over the two seasons, hazelnut seedlings (3-month-old) were placed adjacent to the spore traps. Near sources significantly higher (P. < 0.01) ascospores counts were obtained for branches cut near budbreak compared to those pruned in December in the first season; no significant difference in counts of ascospores were observed in the second season between pruning treatments. For both seasons significantly higher (P < 0.05) counts of ascospores were observed at 6.4 m downwind compared to 6.4 m upwind or 20 m downwind of a source. Ascospore viability, as assessed by staining with trypan blue, was similar for both pruning times at all distances and averaged 50%. At least one infected seedling was obtained for 5 of 7 major rain events regardless of pruning time at sources and 3 of 7 major rain events 6.4 m downwind of a source. All of the 2-year-old potted trees for both pruning treatments at the source and 6.4 m downwind became diseased and > 50% of trees at 20 m downwind became diseased in the 2010 season. Similar to ascospores counts, disease incidence was significantly higher (P < 0.01) in 2-year-old potted trees observed 6.4 m downwind compared to 6.4 m upwind or 20 m downwind in the 2010 season. Significantly higher (P < 0.01) disease incidence in 2-year-old potted trees was observed 20 m downwind compared to 6.4 m upwind in the 2010 season. Downwind disease gradients for both pruning treatments were shallow with slopes that were not significantly different than zero (p > 0.05) for the 2010 season. Based on these results, ascospores from diseased branches pruned from trees in both pruning treatments remained viable, infectious and were dispersed downwind of each treatment. / Graduation date: 2012

Graduation date: 1996