21 CFR § 179.39 - Ultraviolet radiation for the processing and treatment of food.

---
identifier: "/us/cfr/t21/s179.39"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 179.39 - Ultraviolet radiation for the processing and treatment of food."
title_number: 21
title_name: "Food and Drugs"
section_number: "179.39"
section_name: "Ultraviolet radiation for the processing and treatment of food."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "B"
subchapter_name: "FOOD FOR HUMAN CONSUMPTION"
part_number: "179"
part_name: "IRRADIATION IN THE PRODUCTION, PROCESSING AND HANDLING OF FOOD"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 321, 342, 343, 348, 373, 374."
regulatory_source: "42 FR 14635, Mar. 15, 1977, unless otherwise noted."
cfr_part: "179"
---


# 179.39 Ultraviolet radiation for the processing and treatment of food.

Ultraviolet radiation for the processing and treatment of food may be safely used under the following conditions:

(a) The radiation sources consist of low pressure mercury lamps emitting 90 percent of the emission at a wavelength of 253.7 nanometers (2,537 Angstroms).

(b) The ultraviolet radiation is used or intended for use as follows:

| Irradiated food | Limitations | Use |
| --- | --- | --- |
| Food and food products | Without ozone production: high fat-content food irradiated in vacuum or in an inert atmosphere; intensity of radiation, 1 W (of 2,537 A. radiation) per 5 to 10 ft. | Surface microorganism control. |
| Potable water | Without ozone production; coefficient of absorption, 0.19 per cm or less; flow rate, 100 gal/h per watt of 2,537 A. radiation; water depth, 1 cm or less; lamp-operating temperature, 36 to 46 °C. | Sterilization of water used in food production. |
| Juice products | Turbulent flow through tubes with a minimum Reynolds number of 2,200. | Reduction of human pathogens and other microorganisms. |

[42 FR 14635, Mar. 15, 1977, as amended at 65 FR 71057, Nov. 29, 2000]