Dry Cleaning in the Food Industry: Rationale and Challenges

Editors’ note: This is part 1 of a two-part series on dry cleaning. Part 1 looks at the rationale for dry cleaning, and the challenges that can accompany the process. Part 2, which published in the October/November 2021 issue of Food Quality & Safety, focuses on solutions to these challenges.

We tend to think of dry cleaning in the food industry as being related only to those food plants that undertake dry/low water activity (a_w) food and ingredient processing. But, dry cleaning and sanitization can be a valuable option in the control of microbial hazards for any processing plant. In this series of articles, we look at the rationale, challenges, and solutions related to microbial control through controlled use of water, dry cleaning, and other sanitization techniques.

Rationale

The production of dehydrated foods and food ingredients with low a_w, such as cereals, chocolate, cocoa powder, dried fruits and vegetables, dried meats, egg powder, herbs, spices, condiments, milk powder, whey protein powders, pasta, powdered infant formula (PIF), grains, and seeds is popular, due to their long shelf life and less stringent holding and storage condition requirements.

Low-moisture and low a_w foods also have advantages in that they are less prone to spoilage. Although low a_w foods seem to have clear advantages with respect to controlling the growth of microorganisms, there are, nevertheless, major concerns regarding the survival of pathogenic microorganisms, and outbreaks linked to low a_w foods and dry ingredients have been reported. Major foodborne pathogens of concern include Salmonella spp., Bacillus cereus, Cronobacter sakazakii, Clostridium spp., E. coli O157:H7, and Staphylococcus aureus.

Many food processors and consumers mistakenly believe that dried foods are sterile or that microorganisms do not survive in dried food due to their low moisture content. However, many microorganisms, including pathogens, are able to survive drying processes and, while they may not grow, vegetative cells and spores may remain viable for several months or even years. Microorganisms are known to persist longer in dried foods and dry food processing environments than in foods and environments with higher moisture content and low a_w. It’s also important to note that foodborne pathogens in low a_w foods and environments may have an increased tolerance to heat and other treatments that are lethal to cells in high a_w environments, making them very difficult to eliminate in many dry foods or dry food ingredients without compromising the quality of the food product.

Potential sources of microbial contamination in dried foods include incoming raw materials and ingredients, the external environment (surroundings, water, air, pests), inadequate cleaning and sanitation, inadequate processing, and post-processing contamination, mainly through the food plant environment. Primary strategies for reducing microbial pathogens include:

• Supplying specifications segregating hygiene areas to separate dry and wet processing areas;
• Controlling human and material movement in the plant to avoid cross-contamination,
• Implementing effective dry-cleaning and wet-cleaning practices; and
• Employing an effective environmental pathogen monitoring program, particularly in a facility producing ready-to-eat (RTE) foods.

The Food Safety Modernization Act (FSMA), signed into law in January 2011, represents a paradigm shift from reaction-based systems to prevention-based systems and clearly places the burden of assuring food safety on the food manufacturer. The “Current Good Manufacturing Practice Hazard Analysis and Risk-Based Preventive Controls for Human Food,” or the Preventive Controls for Human Food (PCHF) rule, requires food processors to identify “known or foreseeable” hazards in foods, using a risk-based hazard analysis, and identify preventive control(s) to mitigate the hazard identified. In addition, management components such as monitoring; procedures for corrective action, verification, and record keeping; supply chain programs; and recall plans are also required. The FSMA PCHF is based on the modified cGMPs and includes sanitation controls. The PCHF regulation emphasizes environmental monitoring programs, as well as targeted sampling and testing, as appropriate ways to control microbial hazards in RTE foods.