Food Plant Safety

UV Applications for Food and Non-Food Surfaces

Tatiana Koutchma

• Publisher: Academic Press
• Year: 2014
• Print ISBN: 9780124166202
• eBook ISBN: 9780124166677
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Food Plant Safety: UV Applications for Food and Non-Food Surfaces discusses the fundamental principles of ultraviolet (UV) light technology, and gives practical recommendations on UV processes and systems design for specific processing operations, as well as how microbial efficacy of UV light can improve the quality of existing product lines.Innovative research of ultraviolet light for food applications has been growing worldwide. With increased consumer demand for fresher, minimally processed but safe foods, comes the need for novel technologies to meet that demand. Ultraviolet technology has been taking its niche in food production as a non-chemical treatment to control and enhance safety of processing plants and storage facilities.This concise resource covers the fundamentals of this promising technology and its applications; it will benefit a broad audience of professionals in food engineering, processing, and product development, as well as graduate level students.- Focuses on plant processing operations in the food industry- Presents the benefits of UV light technology applications for air quality, and safety of non-food and food contact surfaces- Covers the cost benefits and energy and environmental advantages of using UV technologies

Chapter 1

Introduction

Ultraviolet (UV) light is an economical, nonthermal, and nonchemical intervention toward improved hygiene control measures in the food industry. Sanitation, decontamination, disinfection, and oxidation with UV light is a versatile, environmental-friendly process, which can be easily adapted in the food production and storage facilities to reduce their microbial contamination and consequently to improve safety of finished products. This book is aimed to review basic principles and benefits of continuous UV and pulsed light (PL), available UV and PL sources, their performance characteristics, and commercial systems that can be installed in food facilities to improve microbial quality of the final products. The examples of current and prospective applications of UV light and PL for air purification, water disinfection and treatments of nonfood contact and food contact surfaces, fresh and fresh-cut produce, raw and ready-to-eat meats, seafood, and eggs will be reviewed along with the available units. This book will provide perspective for food manufacturers on utilizing of UV light benefits in their production and storage facilities.

Keywords

Ultraviolet light; ultraviolet commercial systems; food plant safety; air purification; surface disinfection; UV microbial inactivation

During manufacturing process, ingredients, raw materials, semifinished and finished products can be exposed to microbiological cross-contamination from the air, water, and surfaces in food and storage facilities. The traditional approach to controlling such contamination has been to target specific sites within the manufacturing environment with cleaning and disinfection regimes. Ultraviolet (UV) light is an economical intervention toward improved hygiene control measures in the food industry. Sanitation, decontamination, disinfection, and oxidation with UV light is a versatile, environmental-friendly technology, which can be used in the food production and storage facilities to reduce microbial contamination and consequently to improve safety of finished products. UV light has been historically used for purification of air, disinfection of water and wastewater. In the last decades among other novel techniques, UV technology started to emerge in food processing practices because of its broad antimicrobial action, low cost, and nonthermal, purely physical nature. Despite UV light being known for its surface character, the main interest was focused at the application of UV light as an alternative means of food preservation of food fluids with a broad range of UV light transmission (UVT). There is limited research and commercial practices to use UV as an additional step or/and as a processing aid to disinfect nonfood contact and food contact surfaces to reduce risk of contamination and cross-contamination. This book is aimed to review benefits of continuous UV light and pulsed light for the applications to improve safety at the food plants and provide perspective to food processors on applications of those benefits for their production facilities. The current and perspective applications of UV light for air purification, water disinfection, and surface treatments in food processing and storage facilities will be reviewed among with available UV sources and commercial equipment.

Chapter 2

Basic Principles of UV Light Generation

This chapter focuses on the review of the principles of UV generation, available emitting sources of UV light, and their main components. Detailed description of continuous mercury-based UV lamps (low and medium pressure), low-pressure UV amalgam lamps, PL xenon lamps, excimer lamps, and light-emitting diodes is given along with their advantages, applications, and features of the interaction with foods. Efficiency of UV sources is compared based on their technical characteristics and output spectra. The examples of commercial UV systems for food faculties, manufacturers, and specific requirements for food applications are given.

Keywords

UV light generation; UV light continuous sources; emitting spectrum; PL sources; light light-emitting diodes (LEDs); UV source components; UV source efficiency

2.1 UV Rays: Radiation or Light

UV radiation is defined as the portion of the electromagnetic spectrum between X-rays and visible light. The wavelength for UV light diapason ranges from 100 to 400 nm. This range may be further subdivided into: UVA (315–400 nm) normally responsible for tanning in human skin; UVB (280–315 nm) that causes skin burning and can lead to skin cancer; UVC (200–280 nm) called the germicidal range since it effectively inactivates bacteria and viruses. Vacuum UV range (100–200 nm) can be absorbed by almost all substances and thus can be transmitted only in a vacuum or through certain gases like N₂. Radiation from UV light and the adjacent visible spectral range as well as other less energetic types are termed nonionizing radiation. In contrast, ionizing radiation, which includes X-rays, gamma rays, and ionizing particles (beta rays, alpha rays, and protons), is capable of ionizing many atoms and molecules. The absorption of nonionizing radiation, however, leads to electronic excitation of atoms and molecules.

Light is emitted from the gas discharge at wavelengths dependent upon its elemental composition and the excitation, ionization, and kinetic energy of those elements. UV photons have low penetrating power, because the inherent energy of photons is low in comparison with ionizing radiation and belongs to nonionizing radiation. Absorption of nonionizing radiation leads solely to electronic excitation of atoms and molecules as opposed to ionizing radiation that can lead to ionizing effects. However, the excitation energy of UV photons is much higher than the energy of thermal motions of the molecules at physiological temperatures. The latter is of the order of Boltzman’s constant times the absolute temperature that at 27°C amounts to 0.026 eV/molecule (0.60 kcal/mole) in contrast to the 3.3–6.5 eV/molecule (75–150 kcal/mole) available from UV absorption.

2.2 UV Light Sources

The gas discharges are responsible for the light photons emitted from UV lamps.

UV light transfer phenomenon is defined by the emission characteristics of the UV source along with long-term lamp aging and absorbance/scattering of the product. The commercially available UV sources include low- and medium-pressure mercury lamps (LPM and MPM), excimer (EL) and pulsed light (PL), and light-emitting diodes (LEDs). LEDs and ELs are monochromatic sources whereas emission of MPM and PL is polychromatic. Consequently, performance of UV system depends on the correct matching of the UV source parameters, its wavelength and output power, to the demands of the UV application and its characteristics.

2.2.1 Mercury Lamps

The mercury vapor UV lamp sources have been successfully used in air and water treatment for nearly 50 years and well understood as reliable sources for other disinfection treatments that benefit from their performance such as long lifetime, low cost, and quality. Typically, three general types of mercury UV lamps are used: low-pressure (LPM), low-pressure (high-output) amalgam (LPA), and medium-pressure (MPM). These terms are based on the vapor pressure of mercury when the lamps are operating.

LPM lamps are operated at nominal total gas pressures of 10²–10³ Pa that corresponds to the vapor pressure of mercury at temperature of 40°C with no additional cooling system required. The emission spectrum of LPM is concentrated at the resonance lines at 253.7 nm (85% of total intensity) and 185 nm. The wavelength of 253.7 nm is considered as most efficient in terms of germicidal effect since photons are absorbed most by the DNA of microorganisms at this specific wavelength. Light with a wavelength below 230 nm is most effective for the dissociation of chemical compounds. The photons with the wavelength of 185 nm are responsible for ozone production and the combination of both wavelengths is a very effective means for photochemical air treatment. LPM sources provide a high efficiency in inactivating microbial cells and a number of other advantages such as lifetime up to 9000–12,000 h. Standard LPM quartz lamps are available as “ozone-free” and ozone-generating versions, depending on different transmittance properties of quartz glass. For “ozone-free” lamps doped fused quartz is used (TiO₂ to cut transmittance below 235 nm). The US Food and Drug Administration (FDA) regulations approved the use of LPM lamps for water and surface treatment, and they have already been successfully commercialized in food industry (US FDA, 2000a).

More powerful options exist for the future once validated, such as high-intensity lamps and MPM lamps. LPA lamps that contain a mercury amalgam were developed and incorporated into disinfection applications. The lifetime of amalgam lamps can be up to 12,000 h. LPA lamps offer high UVC output, excellent lifetime, good UV efficiency, high temperature stability and enable operation in high ambient temperatures. This combination makes them the right choice for compact, efficient, and economic disinfection and advanced oxidation systems.

MPM lamps are operated at a total gas pressure of 10⁴–10⁶ Pa. Compared to the LPM lamps, the coolest possible temperature of the MPM is about 400°C, whereas it goes up to 600°C and even 800°C in a stable operation and active cooling can be required. The emission spectrum of MPM covers wavelengths from about 250 nm to almost 600 nm, which results from a series of emissions in the UV and in the visible ranges. MPM lamps are not considered to be useful for targeted germicidal treatment. By varying the gas filling, doping, and the quartz material, the spectrum as well as the radiation flux of the UV lamps can be varied and matched to suit specific food processing applications, especially for oxidation or photo degradation.

Ballasts power all lamps. They provide the starting electrical voltage to ionize the gas in the UV lamp and then limit the current to the nominal level. Lamp ballasts can be either magnetic or electronic. The main components of ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Chapter 1. Introduction
• Chapter 2. Basic Principles of UV Light Generation
• Chapter 3. UV Disinfection of Air, Water, and Surfaces
• Chapter 4. Case Studies of UV Treatment of Food Surfaces
• Chapter 5. Principles of UV Surface Process Development
• Chapter 6. Conclusions
• References