Steaming of Dried Produce 2018

Steaming of dried produce: Guidance to minimize the microbiological risk 1 Table of contents Purpose of this booklet 3 Purpose of this booklet Content overview Microbiological food safety for Content overview This booklet helps you to understand steaming of dried produce Microbiological food safety for steaming of dried produce and manage the critical elements that Dried produce (e.g. herbs, spices, (root) 5 Field of application: Dried produce and steaming impact microbiological food safety vegetables, fruits) can be contaminated 6 Steaming during steaming of dried produce. with pathogenic microorganisms Process overview • Why is it important to manage the that survive the drying process or Management of the process steaming properly; contaminate the product at a later stage 8 Best processing practices • What are the main elements to in the supply chain. 9 Maintenance of equipment control during steaming of dried 1 0 Validation produce; For some dried produce categories, Why is validation so important? • What are the main elements to steaming is a frequently applied Microbiological validation study manage for an effective maintenance thermal process to control Microbiological reduction targets of equipment; microbiological hazards (see Examples of safe processing reference conditions • Why is it important to validate and decision tree on page 6 in booklet Steaming of fresh produce (blanching) verify the microbial reduction for a “Drying of produce: Guidance to 1 2 Verification steaming process. minimize the microbiological risk”)*. Why is verification so important? 13 Good Manufacturing Practices (GMPs) On dried produce, pathogenic Why is it important to have GMPs in place? microorganisms do not grow but can Zoning survive and maintain pathogenicity Cleaning for several months or even years. The Environmental monitoring microorganisms that are considered a 14 Record keeping relevant hazard for dried products are Why is it important to store records? mainly Salmonella spp., Shiga Toxin Producing Escherichia coli (STEC) and Listeria monocytogenes. Pathogenic spore-forming microorganisms are usually not considered a hazard in dry products because the toxicity is linked only to vegetative cells that are generated after spore germination. Due to the low moisture present in dried products, spores do not germinate and vegetative cells are not formed. * see www.nestle.com/aboutus/suppliers 3 Field of application: Steaming of dried produce Inactivation of microorganisms in Although steaming of fresh For fresh produce processed with microbiological hazards, the addition low moisture foods, such as dried produce, also known as blanching, drying technologies that cannot of steaming can potentially be applied produce, is very difficult to achieve is not in the primary scope of this be considered a control point for if the inactivation achieved during due to the high heat resistance booklet, process parameters of microbiological hazards (sun drying drying is not sufficient to guarantee developed by microorganisms in dry blanching are given in section and freeze-drying)*, an additional food safety. environments. For this reason, steaming “Validation” on page 11. processing step should be identified. is a technology widely applied for Steaming may potentially be applied The steaming step is generally applied the microbiological decontamination as control measure. after drying (see table below).However, of dried products. It is comprised of to maximize energy efficiency and three steps: pre-heating, steaming For fresh produce processed with reduce quality loss on final products, and air-drying (see below and section drying technologies that may be blanching of fresh produce before “Steaming” for more details). For some considered a control point for drying instead of steaming after drying technological applications, the first can be considered in some cases. two steps (pre-heating and steaming) can be combined. Technologies that cannot be Sun drying considered control points for microbiological hazards Freeze-drying Technologies that may be Convective air considered control points for microbiological hazards Fluidized bed 1 2 3 Dried produce Pre-heating Steaming of Air-drying of Dried and wetting of wet produce wet produce steamed dried produce produce Microwave (also with vacuum) * see decision tree on page 6 on booklet “Drying of produce: Guidance to minimize the microbiological risk” 4 5 Steaming Process overview Pre-heating is applied to wet the pro- Management of the process control parameter for microbiological The steaming of dried produce (herbs, duct surface through the condensation inactivation. To maintain overpressure spices, (root)vegetables and fruits) of steam and makes microorganisms Why is it important to measure in the steaming chamber two valves usually involves the use of satura- more sensitive to heat. In addition to product temperature and steam are present, one at the exit of the ted steam at temperatures between this, it is also used to heat the product pressure in continuous during pre-heating and one at the exit of the 95–130°C in a three-phase process: to a temperature of about 80–90°C. steaming? steaming chamber, respectively. The pre-heating, steaming and air-drying, When saturated steam is applied, continuous monitoring of the steam as illustrated above (page 4). For some Steaming is the central part of the pro- product temperature is the most pressure is important to verify that technological applications, pre-heating cess where microbiological inactivation direct indicator of microbiological the valves seal properly and no steam and steaming take place in the same takes place. The choice of the tempe- inactivation. Thus, temperature should is leaking out of the chamber. Steam processing unit. rature is based on the desired level of be continuously monitored and temperature and residence time should inactivation and the impact on product recorded during steaming. Probes can also be recorded. The drawing below represents a sche- quality (see page 11). be used to monitor the temperature matic overview of the steaming pro- in different points of the product bulk cess. Product temperature, steam tem- Air-drying is necessary to bring the (product batch mixed with air) along perature, steam pressure and residence product moisture back to the initial the steaming chamber. Steam pressure time are the main parameters to control level and to cool the product down. should also be continuously monitored, for a good management of the process. It is usually done using convective hot as it is an indirect measure of steam and cold air in sequence. temperature, and thus an additional Produce in Steam Water Jacket Steam Jacket Temperature probe Air-drying Pre-heating Steaming Air-drying 6 7 Best processing practices Maintenance of equipment ACTIONS RECOMMENDATIONS Why are appropriate calibration Running of tempera- Process parameters must be considered for the worst processing ture profiling in the conditions (e.g. the highest volume throughput, lowest temperature, and maintenance important? product bulk during shortest time, the beginning (start-up) and the end (shut-down) of commissioning the process). Temperature measurements should be done in different Calibration programs for points of the machine using RecordingTemperatureDevices (RTD). measuring devices Dataloggers can also be used if the machine design allows to do so. This will give a set of temperature lines. The lowest temperature line All recording devices should be considered since it represents the worst temperature. (e.g. for temperature and pressure measurements) Continuous recording Product temperature, steam pressure and steam temperature should should be calibrated of product tempera- be continuously recorded during production. Recording Temperature at regular frequency. ture, steam pressure Devices (RTD) and pressure measurement devices should be fitted This should be done and steam tempera- in the steamer at the start and end point of the process to record at least every six ture during every pro- temperatures and pressure. months. For temperature probes an accuracy duction of ± 0.5°C is recommended*. Continuous recording Residence time is one of the key parameters for microbiological Replacement of pressure valves of residence time inactivation. It should be determined for every product type and during every continuously monitored. For continuous processing, it can be defined When the steaming production through running trials using a sequence of product types differing process uses temperatures above 100°C, in colour or shape. This way the end of the batch is clearly visible a pressure tight valve and the time can be measured manually. The parameter which is is needed on the monitored during production is the rotation speed of the mixer, since inlet and outlet of the a fixed residence time corresponds to this speed. steaming chamber to maintain overpressure. Rotary valves are normally used for this Generation of Steam is generated in the boiler at a specific pressure. It is important application. Depending on the type saturated, dry steam to maintain a decrease in pressure along the entire steam line, down of product processed, the deterioration of the to the point of injection into the pre-heating and steaming. This valve due to abrasion from product can differ creates expansion of steam with release of thermal energy to the significantly. The lifespan of the valve should external environment that avoids any formation of condensate. In this be

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