Validation of Individually Quick-Frozen Foods
By Dr. John W. Raede
As I get older, and hopefully wiser, I've made a concerted effort to reduce my intake of certain foods, increase intake of others, and increase my exercise. I decided on walking because it is something I am good at. I had this epiphany recently, when I was down in South America looking at a potential individually quick-frozen (IQF) vegetable supplier, and I realized much of my 30-year career has been spent walking. We walk the fields, product reception, pre-wash, manipulation, blanching, chilling, freezing, packaging areas, and finished-goods freezer. Nothing like a good walk through a process to give you a general idea of what is going on, if you know what to look for. That’s the tough part—what do you look for? In this article, I will walk you through what I look for and why it means something to me.
I started my career in the beef industry at the ranch level. Horseback, truck, and tractor were the standard modes of transportation around the ranch, and not too much walking. I guess you could consider fixing fence a task that required walking, which was a significant amount of the work we did. Although we didn’t walk much, I learned something important from Harold Porterfield (may he rest in peace), ranch owner and my boss/mentor. As we would ride through the herd, he would stop and look at each pair (cow/calf). Being in my early 20s, I would become impatient because I had something more important (I thought at the time) to do like hit the local watering hole. One day, I asked why we had to go through that every time we rode through the herd; I thought we were looking for obvious issues like prolapses, pinkeye, and assorted injuries. He said, “It’s the little things that matter, because the little things add up to big things, and the big things are what will cause you to fail in this business.”
So that is why I walk. I walk and I look for the little things. Walking the fields and then onto the production floor provides you with the sights, smells, sounds, and feel of the process. I thrive on that. I need that interaction to give me an understanding of whom I am dealing with and what we are really going to buy from them. As the old adage states: “Nobody sends you a bad sample.” If you can’t go to the supplier for budgetary reasons, find somebody you trust to get in there and walk that field and factory.
Now, I think if you’ve made it this far into the article, you are preparing to take notes in regard to all these “little things” I am going to drop on you…but that is not the case. Only one big thing matters most in the IQF vegetable world. It is very common in the food industry and is applicable across the food ingredient categories. The one big thing is: cleaning. Yes, that’s it! Well, it comprises a multitude of little things that will be covered further into the discussion.
Here is a basic rundown of how cleaning affects the overall process and product:
1. Cleaning the fields throughout the growing season and prior to harvest prevents foreign material (FM) and microbiological waste from contaminating the harvested product.
2. Washing the product prior to entering the factory removes pesticide residue, microbiological organisms, yeast/mold, and FM.
3. Cleaning the dicer/slicer/chopping equipment throughout the shift reduces the increase in microbial load during the shift (heat generation) and allows operators to either check the blades to identify wear to prevent FM contamination or identify damaged blades and place product on hold back to the last good check.
4. Effective sanitation practices and inspection for wear of equipment in zones 1 and 2 after the blancher and/or lethality step can prevent post-process microbial and FM contamination.
5. Proper freezer coil, conveyor framework, and paneling sanitation inside the freezer prevents microbial harborage and product contamination. Inspection of conveyor belts during the cleaning process can detect abnormal wear and prevent FM contamination.
6. Validated cleaning of equipment, floors, and forklift/pallet jacks in the packaging area prevents microbial harborage from contaminating finished product.
7. Proper cleaning/inspection of finished-product freezer storage reduces the potential for pallet debris, compromised packaging, and structural failure, which can lead to FM and microbial contamination.
If you need additional detailed information on the steps within an IQF vegetable process, keep reading and you’ll find it. The further you delve into the type of process, the greater your understanding of how simple yet crucial each process is to the whole operation. The “little things” are the intricacies involved in each stage of the IQF vegetable process, and how validated cleaning procedures work to prevent the big three risk factors: microbiological, chemical, and physical. To frame this discussion, I’ve broken down the process into seven main sectors:
1. Field Practices
4. Product Manipulation
5. Lethality Step
This is where the whole process starts. I know the current buzzword is “field to fork,” and it is one of the few terms I like to use because it reflects the required approach, especially in the IQF vegetable world. Fields that are free of trash, road debris, used containers, and discarded employee personal protective equipment are a good indicator that the farmer and/or farm manager understands the importance of maintaining a clean environment for the crops to grow and the employees to work in. A clean field is critical with a mechanically harvested crop because if small wildlife, trash, and/or debris are present, the harvester may include them with the intended product.
In some cases, the difference between hand harvested and machine harvested is the potential to increase the risk of FM. Spinach is a product that has an inherent discrepancy between hand and machine harvested. If the product is hand harvested, the risk for field-originated FM is mitigated because of the cutting technique used by the employees. Machine harvested has a higher potential to extract debris during the process. Farmers that employ a Good Agricultural Practices program account for that risk and mitigate it by consistent removal of debris from the fields.
Here is a brief description of the GLOBALG.A.P. program from their website. “The GLOBALG.A.P. Fruit & Vegetables Standard covers all stages of production, from preharvest activities such as soil management and plant-protection product application to postharvest produce handling, packing, and storing. This standard has been successfully assessed against the Global Food Safety Initiative (GFSI) benchmarking requirements and achieved GFSI recognition for scope B1 Farming of Plants and D Pre-Processing Handling of Plant Products.”
Sorting is basically a grading process in the IQF vegetable business. Blemished, defective, and damaged product is removed from a conveyor belt by employees and/or an electronic vision sorter. In my opinion, a combination of both is best. I am all for redundancy in the system. Laser-color sorters are my favorite. A hardwired unit can receive software updates in real time to increase effectiveness. The placement of a laser sorter within the process depends on the type of vegetable material being run. As an example, in an IQF-chopped (diced) operation, the optimum location for the sorter is ideally after receiving. A robust receiving area will utilize a sand/stone removal tunnel and an air separator to remove heavy material.
Multiple validation studies have been conducted in regard to the most effective means to laser-color-sort spinach. The data collected clearly indicated a significant difference in the ability to detect a controlled sample of common types of FM found in harvested spinach that remained on the leaves or conveyor belt after the receiving process. Dry, whole leaves have a higher tendency to not curl around FM; curling shields the object from the near-infrared sensor.
A vigorous and effective wash step is mandatory in the IQF process. Processors are beginning to perform validation studies in their washing steps to understand the effectiveness of their washing process. Performing a validation study of the washing process can add to the sum total of an overall 5-log reduction of Listeria monocytogenes. In addition, to clean potable water with robust agitation, the wash water needs a consistent and validated amount of sanitizer. If the wash system recirculates the water, this variable must be included in the validation study, and in most cases, the ppm of sanitizer should increase. If the correct concentration is not maintained in the water, washing can have the opposite effect and potentially contaminate the product.
The sanitizer most commonly used in wash tanks is chlorine. Consistent monitoring of the amount of chlorine is critical. Documentation of the initial concentration and subsequent checks is a key indicator for me. In addition to the dosage amount, the amount of free chlorine, pH, temperature, and the amount of organic matter (what is in the water in addition to the sanitizer, e.g., soil) all impact the effectiveness of the sanitizer.
Currently, I am monitoring an ongoing validation study of an advanced washing system that utilizes nanosonic technology as opposed to chemical sanitizers used to clean fruit and vegetables. The study will determine the log reduction of L. mono-cytogenes capability of the washing system. If the study demonstrates a consistent, effective log reduction, processors of certain types of vegetables that do not maintain their organoleptic properties (tomatoes, mushrooms, etc.) after certain sanitation processes may achieve a 5-log reduction with minimal blanching to preserve the desirable traits of the sensitive products.
Whatever type of segmenting (cutting, dicing) the product is going through, the potential for FM must be considered in a risk assessment. Performing hourly dicer blade checks, rinsing of the dicer, and employing a vigorous washing system prior to the dicer can mitigate FM entering the dicer. The best method is for the operation to employ two dicers. Based on operational data to determine the frequency checks, the line is stopped and the dicer is removed and replaced by a second unit. This replacement allows for the dicer to receive a full inspection with minimal disruption to the process.
Blanching is the process of scalding vegetables in boiling water or steam, and is a common method for most vegetables in an IQF process. It stops enzyme actions that can cause loss of flavor, color, and texture. Blanching cleanses the surface of dirt and organisms, brightens the color, and helps retard loss of vitamins. It also softens leafy green vegetables like spinach and makes them easier to dice prior to freezing.
Blancher validation and verification is the key to a process under control. Numerous frozen meal assemblers are requiring their suppliers to validate their blanchers to achieve a 5-log reduction of L. monocytogenes. The parameters of the validation study are critical: type of blancher, bed depth of product, type of product, microbial load of the product, belt speed, and customer specification requirements. Most validation studies are performed by an off-site lab because of the pathogens used in the study. In some cases, surrogate organisms are used to inoculate the product if the validation study is performed on-site. Blancher verification is normally performed on an hourly basis and is either digitally recorded and/or documented manually.
My European colleagues are not very happy with the American approach to blanching. They do not want to blanch to a 5-log reduction because, in their opinion, it negatively affects the organoleptic characteristics of the product. I agree with them; however, we are in a risk-averse marketplace that has given zero indication to date of changing.
Tomatoes are usually not blanched because of the degradation to the product texture. Calcium chloride (CaCl) is leached from the tomatoes during blanching. When tomatoes are blanched, a treatment of CaCl is administered prior to blanching. Depending on which side of the argument you are on, whether CaCl is a processing aid or ingredient will determine whether you will use a blanched tomato or not.
I want to spend a little time in this section in regard to the particulars of the freezing process because this is the defining process for this type of product. Product that undergoes rapid freezing moves through a freezing unit on a specialized conveyor belt that creates small ice crystals. The smaller crystals are beneficial in two main ways. The first is that smaller crystals reduce clumping, enabling a free-flowing product, and the other is the preservation of texture and flavor. Juxtapose that with large ice crystals, which are a result of a slower freezing process, usually referred to as a static freeze. Meaning product is placed into a container, as opposed to moving through the freezer unit on a conveyor, and placed into a storage freezer to reach the desired temperature. Large ice crystals can rupture vegetative cells and cause the texture of the product to have a soft mouthfeel. It is imperative to keep the product at a constant storage temperature of 0 °F or lower to maintain the benefits of rapid freezing. Maximum airflow is a beneficial aspect of rapid freezing. One thing I look for in a diced/chopped spinach freezer is when the product appears to be bouncing on the freezer belt. High-velocity air movement ensures a rapid freeze that provides the benefits previously discussed.
This area is the final opportunity to exercise factory-level preventive controls. Microbial, chemical, and FM contamination are still a risk in this area of the factory, and diligence is required. When I walk into this area, I look for indicators of a controlled environment. I look at how much wooden pallet debris is on the floor; you’d be amazed at how that can travel up and into an open container with product in it, causing an FM issue. What type of controls are in place for forklift/pallet jack traffic? Are there separate forklifts/pallet jacks for inside the packaging area and for outside the area? Are the employees that work in that area distinguished by their uniforms, hairnets, or bump caps from the production area? These considerations are for microbial control. Foot and equipment travel are a significant contributor to “microbial travel.”
Each of these processes is simple on its own, yet they are crucial all together for the safe production of IQF vegetables. Along with validated cleaning procedures, these processes are essential to minimize the risk of microbiological, chemical, and FM contamination.
Dr. John W. Raede is the chief food safety officer for National Cortina.