Luke Frederick Laborde

• PhD
• Professor at Pennsylvania State University

Unlike many human pathogens, Listeria monocytogenes can survive in cold, wet environments. Environments like fruit packing facilities. L. monocytogenes has been implicated in outbreaks from tree fruit products. Such outbreaks are serious, as listeriosis has an estimated 94% hospitalization rate and a nearly 16% mortality rate. Other microbes may be...

Background: Listeria monocytogenes can survive in cold and wet environments, such as tree fruit packing facilities and it has been implicated in outbreaks and recalls of tree fruit products. However, little is known about microbiota that co-occurs with L. monocytogenes and its stability over seasons in tree fruit packing environments. In this 2-ye...

We evaluated the ability of two strains of lactic acid bacteria (LAB) to inhibit L. monocytogenes using spot inoculation and environmental microbiome attached-biomass assays. LAB strains (PS01155 and PS01156) were tested for antilisterial activity toward 22 phylogenetically distinct L. monocytogenes strains isolated from three fruit packing environ...

Whole genome analysis was performed on 501 isolates obtained from a previous survey which recovered 139 positive environmental sponge samples (i.e., up to 4 isolates per sample) from a total of 719 samples collected at 40 standardized sites in 3 commercial apple packinghouse facilities (i.e., P1, P2, and P3) over 3 successive seasons in a single pr...

Commercial production of fruits and vegetables on Amish farms provides significant amounts of fresh produce that are regionally distributed through wholesale markets. In response to several multi-state foodborne disease outbreaks linked to contamination of fresh produce, the U.S. Food and Drug Administration (FDA) mandated farm food safety standard...

A 2-year longitudinal study of three tree fruit packinghouses was conducted to determine the prevalence and distribution of Listeria monocytogenes. Samples were collected from 40 standardized non-food-contact surface locations six different times over two 11-month production seasons. Of the 1,437 samples collected, the overall prevalence of L. mono...

Industrial food slicing equipment that is difficult to clean and sanitize can become a reservoir of Listeria monocytogenes. Some commercial mushroom slicing operations have attempted to manage cross-contamination risks by periodically immersing detachable slicer heads in heated water maintained at varying temperatures for different times. In this s...

Background: Multistate foodborne disease outbreaks and recalls of apples and apple products contaminated with Listeria monocytogenes demonstrate the need for improved pathogen control in the apple supply chain. Apple processing facilities have been identified in the past as potential sources of persisting L. monocytogenes contamination. In this st...

This chapter discusses Hazard Analysis Critical Control Point (HACCP) that has emerged as the gold standard for protecting consumers from foodborne illness. The underlying concept behind HACCP is that experience and scientific data must be used to determine process-specific food safety hazards and appropriate, verifiable control measures. The chapt...

Recent produce-associated foodborne illness outbreaks have been attributed to contaminated irrigation water. This study examined microbial levels in Pennsylvania surface waters used for irrigation, relationships between micro bial indicator organisms and water physicochemical characteristics, and the potential use of indicators for predicting the p...

A longitudinal study was conducted to determine the prevalence of Listeria spp. in a commercial fresh mushroom slicing and packaging environment. Samples were collected at three different sampling periods within a 13-month time interval. Of the 255 environmental samples collected, 18.8% tested positive for L. monocytogenes, 4.3% for L. innocua, and...

Penn State Extension conducted on-farm food safety workshops statewide to train fruit and vegetable growers on Good Agricultural Practices (GAPs). These workshops were evaluated using pre- and post-tests to assess the impact of the training on participating growers. Results indicate overall increases in produce growers' knowledge, attitudes, confid...

Factors affecting ultraviolet (UV) radiation-induced degradation of patulin in a malic acid model system, apple cider and apple juice were studied. First-order rate constants (cm2/J) in the model system were not significantly (P > 0.05) affected by pH (3.0–3.6), initial patulin concentration (0–1000 μg/L), glucose (0–10%), sucrose (0–10%) and ascor...

Degradation of the mycotoxin patulin between 25 and 85 °C without and with added ascorbic acid was studied, and the effectiveness of linear and nonlinear models for predicting reaction rates was compared. In agreement with previous reports, ascorbic acid significantly increased (P ≤ 0.05) the rate of patulin degradation at all temperatures studied....

Commercial production of white button mushrooms (Agaricus bisporus) requires a specialized growth substrate prepared from composted agricultural by-products. Because horse and poultry manures are widely used in substrate formulations, there is a need to determine the extent to which the composting process is capable of eliminating human pathogens....

Listeria monocytogenes is a foodborne pathogen of significant concern to the agricultural and food processing industry because of its ability to grow and persist in cool and moist environments and its association with listeriosis, a disease with a very high mortality rate. Although there have been no listeriosis outbreaks attributed to fresh mushro...

Mushrooms do not contribute significantly to dietary intake of nitrates, even when irrigated with water that exceeds the EPA limit of 10 mg NO3-N/L. Mushroom growers should be permitted to use well water with higher levels of nitrates for irrigation. There is no need to purchase and install reverse osmosis equipment to lower nitrate levels in irrig...

As a leading cause of foodborne illnesses, fresh fruits and vegetables have received national attention, recently highlighted by the Food Safety Modernization Act (FSMA) which was signed into law in early 2011 by President Obama. Through this law [P.L. 111–353], the United States Food and Drug Administration will establish mandatory minimum standar...

Mixed-mode surveys present one opportunity for Extension to determine program outcomes at lower costs. In order to conduct a follow-up evaluation, we implemented a mixed-mode survey that relied on communication using the Web, postal mailings, and telephone calls. Using multiple modes conserved costs by reducing the number of postal mailings yet mai...

Major supermarket chains increasingly are requiring their produce suppliers to provide evidence of compliance with on-farm food safety standards, known as Good Agricultural Practices (GAPs). To develop a relevant GAP training curriculum that meets the needs of Pennsylvania growers, supermarkets that operate in the state were surveyed to determine t...

Degradation products of ultraviolet (UV-C, 254 nm) treated ascorbic acid (AA) are reported. Analysis by high-performance liquid chromatography-mass spectroscopy (HPLC-MS) conducted in a 0.5% malic acid model juice system (pH 3.3) demonstrated increased degradation of AA above untreated controls with concomitant increases in dehydroascorbic acid (DH...

Introduction The HACCP Concept Prerequisite Programs Developing a HACCP Plan Use of HACCP in the Vegetable Industry Summary References

Ultraviolet radiation induced degradation of ascorbic acid in a model apple juice system and in apple juice was studied using a collimated beam batch UV reactor. In the model system, ascorbic acid degradation was more rapid at higher dose levels and the reaction accelerated with increasing exposure time. Ascorbic acid degradation significantly (P <...

Degradation products of ultraviolet (UV-C, 254 nm) treated ascorbic acid (AA) are reported. Analysis by high-performance liquid chromatographyÀmass spectroscopy (HPLC-MS) conducted in a 0.5% malic acid model juice system (pH 3.3) demonstrated increased degradation of AA above untreated controls with concomitant increases in dehydroascorbic acid (DH...

Evaluation of program impact is needed to show the worth of a program. There are few studies of training program impact on food safety behaviors within food production and processing settings. Our research objectives were to develop, implement and evaluate a pilot food safety educational program for Hispanic workers in the mushroom industry using t...

Sometimes educational materials do not work because they are designed without examining the worksite social and environmental factors affecting the target audience. Educational materials based on application of theory-based models may address more effectively the cause of food safety problems. The objective of this project was to use the Health Act...

The use of water flotation tanks during apple packing increases the risk of contamination of apples by spores of Penicillium expansum, which may accumulate in the recirculating water. Routine addition of sanitizers to the water may prevent such contamination. Sodium hypochlorite (NaOCl), chlorine dioxide (ClO2), and electrolyzed oxidizing (EO) wate...

ABSRACT Destruction of Escherichia coli O157:H7 in apple cider treated with fumaric acid and sodium benzoate (0.15% and 0.05% w/v, respectively) was determined under pH and storage temperatures that commonly occur in apple cider. At 5°C storage, while destruction of E. coli O157:H7 in the presence of preservatives increased with time, there was lit...

 Computer-based training is increasingly favored by food companies for training workers due to convenience, self-pacing ability, and ease of use. The objectives of this study were to determine if personal hygiene training, offered through a computer-based method, is as effective as a face-to-face method in knowledge acquisition and improved attitud...

The ability of Escherichia coli O157:H7 to penetrate and grow within punctures, fresh-cut surfaces, and calyces of Golden Delicious apples was investigated. A three-strain cocktail of E. coli O157:H7 resistant to ampicillin was used to inoculate fresh and 48-h-old punctures, fresh-cut surfaces, and open or closed calyces. A concentric cutting proce...

The quality and value of fresh mushrooms are often diminished by the presence of high bacterial populations that cause a brown, blotchy appearance. The objective of the present research was to evaluate the addition of hydrogen peroxide and/or calcium chloride to irrigation water as a means to reduce total bacterial populations on fresh mushrooms. C...

The effect of storage temperature (4 °C, 10 °C, and 20 °C) on retention of folate, carotenoids, and other quality characteristics in commercially packaged fresh spinach were determined. Based on visual color and appearance, spinach was unacceptable after 8 d, 6 d, and 4 d at 4 °C, 10 °C, and 20 °C, respectively. Color differences (AE), chlorophyll...

The microbiological method for the determination of folate in plant foods uses the growth response of folate-dependent Lactobacillus rhamnosus in extracts that have been enzymatically treated to release the bound vitamin. However, the use of cryoprotected cultures is hampered by low recovery of the microorganism after extended frozen storage times....

Spores of Penicillium expansum, the primary organism responsible for the occurrence of patulin in apple juice, were exposed to electrolyzed oxidizing (EO) water in an aqueous suspension and on wounded apples. Full-strength and 50% EO water decreased viable spore populations by greater than 4 and 2 log units, respectively. Although EO water did not...

Studies were conducted to investigate changes in microbial levels during mushroom composting and the destruction of human pathogens during Phase II pasteurization and conditioning. Total aerobic bacteria and coliform levels in compost prepared on a model mushroom farm were monitored throughout a complete crop cycle. There was little change in total...

Foodborne illness due to consumption of fruits and vegetables appears to be increasing in the USA. Fruits and vegetables can become contaminated with pathogenic and spoilage microorganisms throughout the preharvest and postharvest systems. Wild and domestic animals, soil, feces, irrigation water and human handling are potential preharvest sources,...

Low temperature heat treatments applied to potatoes (cv Atlantic, Snowden, and Pike) prior to retorting were evaluated for their effect on sloughing in canned potatoes. Blanching in water for 30 min at 60 - 77C before retorting decreased potato breakage, brine turbidity, and brine soluble solids without adversely affecting firmness or color. Low te...

E. coli O157:H7 reduction on inoculated alfalfa seeds was investigated using acid scarification treatments with or without subsequent application of sanitizers. Scarification with 0.1 to 2N H2SO4 for 2.5 to 45 min did not affect (p ≤ 0.05) seed viability. E. coli O157:H7 was reduced by 2.1 to 5.0 logs after treating with 0.1 to 2N H2SO4 for 5 to 20...

The effect of solutes on the formation of zinc complexes of chlorophyll derivatives in processed green vegetables was studied using a pea puree model system containing added Zn2+ and heated at 121°C for 30 min. Divalent cations decreased the pH of unheated purees and zinc complex formation after heating, suggesting that the pH-lowering effect of di...

Chlorophyll degradation and zinc complex formation with chlorophyll derivatives in processed green vegetables were studied using pea puree containing added Zn2+ and heated at 121°C for up to 150 min. Chlorophyll a decreased to trace levels after 20 min as zinc complexes of pheophytin a and pyropheophytin a were formed. Further heating decreased zin...

Zinc complex formation with pyropheophytin a was studied on vegetable purees in order to further understand metallo complex formation during thermal processing. Zinc pyropheophytin a formation was dependent on added Zn2+ ion, pigment concentration, and pH. Pea puree heated 60 min at 121 °C with 150 and 300 ppm added Zn2+ ion contained 3 and 9 times...