Andrew Paul Breksa

Research is needed to improve walnut drying throughput and energy consumption in hulling plants, but current methods for sampling nuts in commercial drying bins and measuring nut moisture content limit the capacity to investigate the drying process thoroughly. A novel apparatus for obtaining walnut samples at multiple depths and locations in stadium drying bins and a novel rapid method for accurately determining walnut in-shell moisture content were developed. A second rapid moisture measurement method involving near-infrared light (NIR) was also investigated. The sampling apparatus consisted of three sampling columns installed in each walnut drying bin. Each column had gate valves at four elevations, admitting approximately 30 in-shell walnuts to rectangular buckets hanging on a cable just below each gate valve. To collect samples, the gates were opened and closed, the buckets were withdrawn, the nut samples were collected and sealed in labeled bags, and then the buckets were returned to the column to be ready for the next sampling interval. This configuration, sampling nuts at four levels across three locations in the drying bin, allowed better moisture content variability investigation during in-bin walnut drying. The rapid moisture content measurement method consisted of selecting twelve representative in-shell walnuts from each sample and grinding them in a mill. Twelve grams were sub-sampled from the well-mixed ground material and dried in an oven at 105 ± 1 °C for 3 h, then reweighed to determine moisture loss. The coefficient of variation for sub-samples within an individual sample (n = 4) averaged 2.65% for moisture contents ranging from 6% to 47% dry basis. The rapid moisture content measurement method reduced the drying time from 24 h to 3 h compared to conventional oven drying method, with an accuracy of ±0.5 to 1.5% of the full moisture content range. The best correlation observed between the NIR methodology and the rapid moisture content method was 0.74 R². These new in-bin walnut sampling and moisture-content measurement methods will accelerate future research aimed at improving walnut drying at commercial huller facilities.

Recent efforts have been made to develop hot-air-dried chips as a value-added product for persimmon fruit (Diospyros kaki). However, the long-term quality of this product and its dependence on processing conditions and packaging type have not yet been explored. Hence, in this work, chips were prepared from “Hachiya” persimmon fruit in 2 ways: 2 mm thickness fruit slices, hot-air-dried for 5 hours (Preparation 2–5), and 6 mm slices, dried for 10 hours (Preparation 6–10). The dried chips were then packaged into 2 bag types (plastic zip-top and metallized polyethylene terephthalate (Met-PET) with desiccant packets), stored under ambient conditions, and sampled for moisture-related, microbial, texture, and chemical quality traits throughout the 1-year storage study. It was found that–with the exception of a marked decrease in ascorbic acid (vitamin C)—all 4 Preparation/Packaging combinations yielded products that maintained acceptable color, microbial, nutritional, and textural quality throughout the entire study. Compared to Preparation 2–5 chips, Preparation 6–10 chips generally had lower contents of healthy nutrients—antioxidant compounds, ascorbic acid, and carotenoids. Evidence of invertase activity was found for Preparation 6–10 chips but not for Preparation 2–5 chips. For both preparations, the contents of ascorbic acid and carotenoids experienced time-dependent decreases. Plastic zip-top bags and Met-PET bags with desiccant packets performed equally well as packaging for most of the quality metrics tracked during this study. Overall, this work has demonstrated that hot-air-drying of persimmon slices is a promising approach to create a value-added product with at least one year of shelf-life.

A method for the identification and quantification of citrus limonoid glucosides in juices, based upon high performance liquid chromatography (HPLC) separation coupled to post-column reaction with Ehrlich’s reagent, has been developed. This method utilizes a phenyl stationary phase and an isocratic mobile phase. Limit of detection for the method was determined to be 50 ng of limonin glucoside. Limonin glucoside and the other limonoid glucosides tested responded equivalently to the post-column reaction with Ehrlich’s reagent suggesting that limonin glucoside may be used as a surrogate for the quantification of other limonoid glucosides, including nomilin, deacetyl nomilin, nomilinic acid, deacetyl nomilinic acid, and obacunone glucosides. For most juice samples, no sample treatment is required to determine limonin glucoside content. Concentration by solid phase extraction is recommended for juices with low levels of limonin glucoside and to facilitate the detection and quantification of other limonoid glucosides present at low concentrations. With the exception of blood oranges, the method was successfully applied to the analysis of juices from a variety of citrus varieties.

BACKGROUND: Modern Citrus cultivars are thought to have arisen from three parents: the pummelo, the mandarin, and citron. Taxological and genetic data support that sweet and sour oranges share a common parentage. However, as their name suggests, the organoleptic properties of the fruit from these two families is distinctly different. Analysis of the limonoid content of sour orange varieties has been limited.RESULTS: Juice samples prepared from a selection of sour orange cultivars were evaluated for their limonoid A‐ring lactone, aglycone, and glucoside contents. Limonoate A‐ring lactone concentrations ranged from 11.1 to 44. 9 mg L⁻¹, whereas nomilinoate A‐ring lactone levels were found not to exceed 1.2 mg L⁻¹. Total limonoid aglycone and total limonoid glucoside concentrations varied from 2.4 to 18.4 mg L⁻¹ and from 149.0 to 612.3 mg L⁻¹, respectively. Limonoid glucoside profiling by liquid chromatography–mass spectrometry suggest that the sour oranges are distinctly different from sweet oranges and other citrus species.CONCLUSION: Limonoid aglycone and A‐ring contents across sweet and sour oranges are similar, whereas limonoid glucoside profiles are distinctly different. Juice prepared from Citrus maderaspatana had the highest limonoid concentrations among the samples tested and could potentially be used for the isolation of limonoid A‐ring lactones and glucosides. Published 2011 by John Wiley & Sons, Ltd.