Stanley E. Prussia

RELATING X-RAY ABSORPTION TO DENSITY AND WATER CONTENT IN APPLES

X-ray computed tomography (CT) was used to image interior regions of ‘Red Delicious’ apples under varying moisture and, to a limited extent, density states. Images were actually maps of x-ray absorption of fruit cross-sections. X-ray absorption properties of ‘Red Delicious’ apples were evaluated using normal apples alternately scanned and sequentially freeze dried, fruit affected by watercore disorder, and normal apples freeze-dried to varying levels. The studies were designed to allow quantification of the x-ray absorption coefficient associated with the dry solids portion of the fruit and the x-ray absorption coefficient associated with moisture. The coefficients associated with moisture were in the vicinity of 0.0191 mm–1 and 0.0182 mm–1, the expected value for water and ice, respectively. The coefficient associated with the dry solids was not significant from zero, due in part to scanner resolution limits, limited dynamic range in density values, and to variation in the physical density measurements. The results of this study suggest that internal differences in x-ray absorption within scans of fruit cross-sections are largely associated with differences in volumetric water content.

ESTIMATING IMPLICIT MARGINAL PRICES OF QUALITY CHARACTERISTICS OF TOMATOES

A hedonic price function is developed for estimating the implicit prices for selected quality characteristics of fresh tomatoes at three points in the marketing season. The estimation of this function, proposed as a method of evaluating change in the post-harvest system, is accomplished using a flexible functional form. Those quality characteristics that most affect the price of tomatoes can help determine the economic feasibility of alternative handling techniques or new technologies.

Effect of Maturity and Storage Time on the Bruise Susceptibility of Peaches (CV. Red Globe)

ABSTRACT Peaches (cv. Red Globe) were divided into three maturity groups and stored at 4°C for specified lengths of time before being bruised by a pendulum impactor at three energy levels. Bruise volume (BV) and susceptibility (BS) were measured in the bruised peaches. Mechanical properties (puncture force, failure stress, and failure energy) were determined by using an Instron Universal Testing Machine. No significant changes in BS and BV were observed for fruit impacted up to 14 days of storage, then both BS and BV increased with storage time. The most mature peaches were more susceptible to bruising and had larger bruise volumes than the least mature peaches; whereas, the differences between least and medium maturity peaches were not significant. Puncture force, failure stress, and energy generally decreased with storage time and maturity. Both tensile stress and puncture force showed promise as an indicator for evaluating the bruise susceptibility of peaches to impact..

MODELING BLUEBERRY FIRMNESS AND MASS LOSS DURING COOLING DELAYS AND STORAGE

Blueberry mass and firmness losses were measured to determine the effect of cooling delays at selected temperatures in postharvest environments. Models were developed from the slopes of firmness and mass values plotted against time for four temperatures (4°C, 21°C, 27°C, and 32°C) and 95% relative humidity. The models were validated by holding other sets of blueberries at three temperatures (21°C, 27°C, and 32°C) and at 95% relative humidity for cooling delays of 0, 2, 4, 8, 12 and 24 h before storage at 4°C and 95% RH up to 96 h. The models developed were suitable for evaluating the benefit of lowering temperature during cooling delays of selected durations or the benefit of reducing cooling delays at specified temperatures. The impact of cooling delays was less than expected when compared with losses caused by low-temperature storage for only four days. Additional studies are needed to model the effect of various relative humidity levels and to learn the extent of variation in the rate constants for different cultivars and different crops.

Dynamics of Rabbiteye Blueberry Fruit Quality in Response to Harvest Method and Postharvest Handling Temperature

Abstract Research was conducted to understand the effect of harvesting method and postharvest temperature on fruit quality of ‘Brightwell’ and ‘Tifblue’ rabbiteye blueberries (Vaccinium ashei Reade). Mass loss, firmness and fruit respiration were measured under refrigerated (1°C) and ambient (22°C) conditions for both machine harvested (MH) and hand harvested (HH) berries of each cultivar. Few differences were found between cultivars for the various postharvest quality parameters. Firmness of MH blueberries was diminished by an overall average of 36.2% as compared to HH berries. MH berries placed at 22°C had a mass loss rate of 2.6% per day as compared to 0.2% per day at 1°C during the first two days of storage. Respiration rate of MH berries at ambient temperature was 31.1% higher than HH berries. Refrigeration reduced respiration rates by an overall average of 79%. Refrigerated HH blueberries had the best overall fruit quality after storage, and firmness measures suggested that HH berries had an extended shelf-life of about one week as compared to MH berries. Thus, MH and HH fruit differ in their postharvest handling needs. Also, multiple quality measures are valuable in more clearly assessing fruit Storage life.

VISUAL INSPECTION OF AGRICULTURAL PRODUCTS MOVING ALONG SORTING CONVEYORS

ABSTRACT Two methods of presenting product for visual inspection were compared by measuring the accuracy of the decision process. Simulated products (plastic balls) with random defects were video taped from two different directions (side-to-side and moving toward the inspector). Fifty subjects that viewed the tapes had a 23% increase in their decision accuracy when the product was moving toward them compared to side-to-side. Slow motion analysis of the tape showed that 15% more defects were visible from the end than from the side. The difference between the performance of the inspectors and the actual increase in defects visible to them indicated that ergonomic principles raised the accuracy of the decision process by eight percentage points. Results from an equation developed for calculating the visible surface area of the balls compared favorably with the number of defects visible (13% compared to 15% improvement).

FILTER DESIGN FOR OPTIMAL FEATURE EXTRACTION FROM X-RAY IMAGES

X-ray linescanning is beginning to be established as an alternative tool for non-destructive produce inspection when internal defects are expected. Image analysis based techniques are being increasingly used for quality evaluation and classification of fresh fruits and vegetables. However, noise removal and feature extraction techniques suitable for particular applications need to be identified before a classification system can be developed. This study focuses on the design of prefiltering steps which will lead to optimal defect detection. Autocorrelation and variogram analyses were performed on water CT scans, water linescans, and plexiglass linescan images for purposes of quantifying instrument related noise. Little correlation was observed in water CT and plexiglass linescan images, which implied that a Gaussian filter may be appropriate for noise removal from linescan images of fruits prior to removal of edge features associated with defects such as bruises. A 5 iA5 Gaussian kernel gave significantly (P iU 0.05) better discrimination based on experimental results for enhancing bruise features in apples and disease features in onions. This result confirmed a rule of thumb in terms of filter design based on image statistics. In instances where morphological operators were used, prefiltering masks were not found to be significant at the 5% level. There was a strong correlation between the image signal and pixel location in linescans of water with a free surface. This correlation is believed to be caused by waves due to motion, suggesting a need for frequency domain filtering in the case of water transport.

Harvesting, Handling, and Holding Fruit

The quality of processed fruit products depends on the quality of the incoming fruit, which in turn depends in large part on how the fruit is harvested, handled, and stored. Although processors can use fruit that is unacceptable as a fresh product, the costs of sorting, trimming, and related operations must be considered. Thus, an understanding of the operations necessary to deliver quality fruit to a processing plant is important to maintaining economic processing operations.

Ergonomics of manual harvesting

Manual harvesting has many advantages compared with the mechanical harvesting of most fruit crops. The most important advantage is visual image processing ability which enables workers rapidly to detect fruit suitable for harvest and direct their hand to the fruit selected for detachment. Lacking the necessary computer based image processing equipment, designers of mechanical harvesters have settled for mass removal approaches that typically results in more damage than normal when fruit is harvested individually. Although manual harvesting has the disadvantage of low capacity, it is expected that much of the worlds fruit will continue to be harvested by hand for the foreseeable future. Several ergonomics principles that relate to manual harvesting are discussed. Methods for improving worker conditions and productivity are presented. Worker positioners increase productivity by 20 to 40% and enable use of sun shades, fans, conveyors and other devices that increase comfort and reduce fatigue. Testing and training can yield substantial benefits from small inputs. Tests for visual acuity, colour sensitivity, strength, etc, can help managers assign tasks to the most suitable workers. Training programmes help workers to have a clear mental picture of acceptable fruit and encourage compliance with handling, safety and other procedures. Satisfaction of human drives such as thirst, hunger, thermal comfort and avoidance of pain results in long-range benefits.

APPARENT MODULUS OF ELASTICITY FROM FIRMTECH 2 FIRMNESS MEASUREMENTS OF BLUEBERRIES

The firmness of blueberries and other small fruits can be measured rapidly with a FirmTech 2 Fruit Firmness Tester. The output of the instrument is the slope of a chord joining selected minimum and maximum forces on a force/deformation curve. The overall objective of this study was to improve the firmness measurements obtained with the Firm Tech 2. In this study, both simulations and tests with rubber balls showed that firmness measurements of a single ball increased as minimum or maximum force was increased. If repeatable results are to be obtained from the FirmTech instrument, standard values for the force settings must be established. Equations from ASABE Standard S368.4 were adapted for calculating the apparent modulus of elasticity (Ea) for both parallel plate and single plate compression using FirmTech 2 output. Ea values for a simulated force/deformation curve with deformation taken to the 3/2 power were the same when calculated using the ASABE equations and when calculated using the equations developed, regardless of which combination of minimum and maximum force was selected. When rubber balls with three diameters were compressed with a universal testing machine, the Ea values calculated from the ASABE equations were similar to those calculated using the equations developed in this study. The firmness of blueberries was measured using both the FirmTech 2 and the universal testing machine. The Ea values were calculated using the equations developed in this article and compared to values calculated from the universal testing machine curves using the ASABE equations. Results indicated the loading applied by the FirmTech 2 support plate was somewhere between a parallel plate and a single plate compression test. Additional research could show benefits from using the equations developed in this study for calculating Ea from loading curves obtained using universal testing machines.