Postharvest and Refrigeration Group Technical University of [email protected] www.upct.es/gpostref
Prof. Dr. Francisco Artés CaleroAgronomist Engineer PhD
Refrigeration Engineer
TECHNOLOGY OF MINIMALLY FRESH PROCESSED
(FRESH-CUT) PRODUCE: UNIT OPERATIONS
INDEXMINIMAL FRESH PROCESSING
TECHNIQUES FOR KEEPING QUALITY OF MFP COMMODITIES• Temperature management • Disinfection• Enzymatic Browning Inhibition • Modified Atmosphere Packaging
FLOW DIAGRAM OF ESSENTIAL STAGES AT INDUSTRIAL SCALE • Field operations and harvesting• Transport, receiving and quality control• Prewashing, precooling and cold storage• Conditioning and reducing size• Washing, rinsing, drying and mixing• Associating, Weighting and MAP• Weight, metals and quality controls• Picking, shipping and commercial distribution
SOME OTHERS DESIGNING CONSIDERATIONS
EXAMPLES OF INDUSTRIAL LINES
SUMMARY AND REFERENCES
MINIMAL FRESH PROCESSINGMinimally fresh processed (MFP) or fresh-cut commodities should be prepared and handled by methods to maintain their living fresh state and quality attributes while ensuring food safety and providing convenience to consumers.
The current trend in the minimal fresh processing industry forproduces preservation is to apply combined procedures in order to reach a maximum antimicrobial efficiency, without undesirable effects, with a minimum sensorial deterioration and loss of nutritional value.
Combined single and slight processing operations leading to minimal changes in the original appearance and quality attributes are
• defoliating • cutting • trimming • shredding • peeling• washing • decontamination • dipping • rinsing • slicing • removing seeds, etc. • modified atmosphere packaging (MAP).
MFP products keep their tissues alive and should be preserved against • pathogen microorganisms (producers of toxins)• loss of
- weight - nutritional value - sensorial quality.
The main modifications suffered from the whole original product are • mechanical
- elimination of the uneatable parts - size reduction• physiological
- stimulation of the respiratory activity and ethylene emission • biochemical
- undesirable oxidative enzymatic reactions- the production of compounds able to alter
* flavour * nutritious value * safety of commodities- degradation of vitamins
Minimal processing eliminates any uneatable part, but destroying plant cells and tissues, which increases
• respiration • ethylene production • browning • senescence• nutrients release from cells • microbial spoilage.
Wounding induces undesirable changes in colour (browning), flavour, texture, and nutritional quality (sugars, acids, vitamins) leading to a shorter shelf-life than that of the whole product (from several months or weeks to only about 7 to 15 days).
Shelf-life is affected by• pre-processing factors
- varieties - cultivation - harvesting - ripening stage.• processing factors
- precooling - trimming - cleaning - conditioning - cutting - peeling - washing/disinfecting - rinsing/drying - packaging
• distribution conditions - temperature - RH - atmosphere - duration.
Consequently MFP must be elaborated under highly integrated systems where all steps should be considered in conjunction withthe others.
In this way, the keys for production of safe MFP are• screening materials entering the processing chain• suppressing microbial growth• reducing the surface microbial load• preventing re-contamination.
One of the main impediment for the minimal processing industry expansion is having practical technology to keep overall quality for enough time to guarantee long distance delivery.
In addition, the real influence of conventional and emerging processing systems on overall quality of MFP is not yet well known.
The industry need to dedicate wide efforts and resources for:• designing new industrial facilities • developing and operating in all factories
- good agricultural practices (GAP) - good manufacturing practices (GMP) - sanitation standard operating procedures and microbial testing - HACCP programmes.
Growers, producers, manufacturers and shippers must made great effort to implement GAP and GMP for reducing microbial safety hazards. It must be emphasized the need of implanting right HACCP programs, to guarantee safety to consumer, because shelf life frequently doesn't overcome the time needed to carry out the microbial analysis.
It should be also considered that raw plant materials often do not come from one single origin, and factories often works with produces coming from diverse countries and/or different production systems.
SOCIAL DEMANDS INAGROFOODS
AGRICULTURE
ENVIRONMENT
GAPGAP GMPGMP
I P M
MFP COMMODITIES
To achieve MFP fruit and vegetables with fresh-like high quality, safety and nutritional value it is needed to introduce or combine effective decontamination techniques.
Major current techniques for keeping quality of MFP produces are• chilling combined with MAP • chemical preservation
- antioxidants - chlorine - antimicrobial solutions - acidulants• mildheat treatments (40-50°C) followed by a quick cooling • oxidation/reduction potential
It is commonly used disinfection agents like NaClO and acidification when washing. Generally regarded as safe (GRAS) processing aids,mainly anti-browning compounds and NaClO, usually require no labelling if they have no residual action on the product.
TECHNIQUES FOR KEEPING QUALITY OF MFP COMMODITIES
Main emerging techniques are• new antimicrobial solutions (ClO2, H2O2) • UV-C • O3• superatmospheric O2 • noble gases • electrolized water.
When designing new industrial factories the possibility of implanting these emerging techniques should be took into account.
Temperature management (0 to 5ºC) is the single most useful technique to minimize the effects of wounding and microbial growth in MFP produces. It must be considered that
• commodities are often submitted at higher temperatures, especially in the retail sale display.
• storage temperature also determines respiration rate of the produce and changes in atmospheres within packages
Disinfection
• Incoming vegetables are covered with soil, mud and sand. Hence, the raw product should be carefully cleaned before processing.
• The most widely used antimicrobial washing solution is NaClO, and its antimicrobial activity is related to the concentrations of ClOH. Thus to maximize the proportion of the active chlorine form, the optimum pH range is 6.5-7.5.
• The use of chlorinated solutions has disadvantages- NaClO has an affinity for organic matter and the amount of free available chlorine constantly decreases during washing step. - there are concerns over the fact that food constituents may react with NaClO to form trihalomethanes, some of which are mutagens.
• To minimize risks of excessive microbial load, a good program ofcleaning and maintenance of equipments, as well as avoiding reconta-mination of products after disinfection should be implemented.
Enzymatic Browning Inhibition
• Browning may be prevented by - heat inactivation of the enzyme - exclusion, removal or excess of O2 and phenols- lowering the pH to 2 or more units below the pH optimum- addition of PPO inhibitors
• The most common method for inhibiting enzymatic browning is theaddition of reducing agents to the dipping solution, which reduce the enzymatically formed quinones back to o-diphenols.
• Ascorbic acid is probably the most suitable agent. However, somecombinations of various substances and MAP must be used.
• For minimizing browning it should be used inox. stainless steel or plastics materials in contact with the product, avoiding metallic ions (particularly Cu++ ).
Modified Atmosphere Packaging
• The combination of chilling and MAP is the most widely used preservation technique for MFP produces. MA are generated by therespiration of MFP product (passive MAP) or attained by a gas flushing (active MAP). In this last case, adequate devices should be designed.
• MAP minimizes wilting, discoloration, and microbial growth; however, it may provoke changes in colour, texture, flavour, and in the commercial value of the commodity.
• The film permeability is crucial because it must allow the right O2 and CO2 exchange between the MFP produce and the atmosphere to reach the desired gas composition within bags. The most appropriate films are in general selectively and highly permeable to O2 and CO2.
• Low O2 reduces the respiration rate in proportion to the O2 level, but a minimum of ≈ 1-3 kPaO2 is required to avoid anaerobic respiration and the generation of off-flavours.
Product Atmosphere Potential % O2 % CO2 Benefit
Broccoli 2 – 3 6 – 7 A = ExcellentCauliflower 2 – 5 2 – 5 B – C = Fair Celery 4 – 5 10 – 15 ACucumber 3 – 5 0 B – C Fennel 2 – 6 10 – 20 AKohlrabi 5 10 – 15 ALettuce (green) 1 – 3 5 – 10 A Lettuce (pigmented) 2 – 4 2 – 6 AMelon USA 3 – 5 0 A – B Melon Spain 4 – 6 10 – 13 AOnion 2 – 5 10 – 20 APepper USA 3 – 5 5 – 10 B Pepper Spain 5 – 7 10 – 15 A – B Leek 1 – 2 3 – 5 BSpinach 1 – 3 8 – 10 A – B = Good Tomato 3 – 5 0 – 1 A – B
Harvest& Field
Operations
Transportto Factory
Receiving,Sampling,& QualityControl
Washing *Whole Plant
Organs
Boxing & Controlsof Weight, Metals,
& Quality
Chilling StoragePicking &Palletizing
RemovingUneatable
Parts
Sorting &Classification
Precooling& Chilling
Storage
Cutting,Trimming
WashingDisinfection
Rinsing,Dewatering
ModifiedAtmospherePackaging
Associating &Weighting
Mixing*
Flow diagram of essential stages in the industrial process ‘D
irty’Zone
‘Clean’Z
one
* OPTIONAL
Shipping &CommercialDistribution
ReceivingSampling
Precooling
Chillingstorage
‘Dirty Zone’‘Clean Zones’
Whasing
Rinsing
Conditioning
Drying
Weighting
Packaging
Weight & metals ontrol
Qualitycontrol
Picking & Chilling storage
Shipping
Peeling, Cutting
Gratting, Diccing
Quality Control
FIELD OPERATIONS, HARVESTINGThe quality of raw material depends on the cultivation conditions
• irrigation • climate • fertilization
They can modify the physiological behaviour and suitability for the minimal processing of raw material and the quality of MFP products.
The main preharvest and harvest conditions which affect the fruit and vegetables quality and shelf-life are:
• genetically controlled factors (cultivar, strain) • climate conditions (light, temperature, RH, wind, rain fall) • soil conditions (type of soil, pH, moisture, microflora, mineral
composition) • agricultural practices (fertilizers, pesticides, growth regulators,
irrigation, etc.) • harvesting (kind of harvest, temperature, RH, etc.).
Harvesting is a crucial operation, and optimum date may be estimated in advance by crop scheduling systems. Products should be harvested healthy, freedom from defects and with a firm texture to
• minimize losses • reduce mechanical damages during handling• limit the growth of microorganisms.
Special attention will be paid to microbial contamination during the cultivation, harvesting and transportation to the factory, trying to reach the minimum in the intact products
The initial qualitative and quantitative microbial load of raw materials is decisive for microbial development from harvesting to throughout all processing steps and determines the final content in the MFP product.
Regarding raw materials, the industry is highly exigent in • strict hygienic requirements • great overall quality
In order to assure a high quality of raw materials, the codes of GAP must be implemented and respected.
TRANSPORT, RECEIVING, QUALITY CONTROLThe products to be processed should be harvested the most recently
possible. They must be gentle transported in boxes or bins, and are usually received in the factory from the field in tows or small trucks at ambiance temperature for short distances, or in refrigerated trucks if it takes several hours.
At reception a sampling, traceability and quality control system should be implemented, for what the industry should have a suitable laboratory.
Raw materials can become contaminated with pathogenic micro-organisms while growing in fields or during harvest, transport, handling, processing, distribution and preparation.
There is a need for evaluation of the quality of fresh produce at receiving for safety aspects as
• pesticide residues • microbial load • toxic metals • naturally present undesirable compounds • plant growth regulators
RECEIVING, CLEANING AND HANDLING
PREWASHING, PRECOOLING, COLD STORAGE
Pre-washing with tap water and specific dry cleaner could be considered, in order to remove dirt, plagues, agrochemicals and other foreign materials from raw materials, besides decreasing the microbial load (in beets or spinaches).
As the raw material quality, both chilling treatment before processing and correct cold storage conditions, are vital for the production of high quality MFP produces.
Precooling raw materials to 1-2ºC is used by forced air, hydrocoolingor vacuum cooling depending on the commodities.
Chilled raw materials are stored until processing, usually at 0 to 5ºC, according to demand of temperature, RH and ethylene production and sensitivity. Separate cold rooms to attempt these storage claims must be designed.
PRECOOLING
• Forced Air Cooling• 68.000 kg/day• 5 h/cycle. 20 ºC => 2 ºC
MÓDULOS DE TARIMA MÓVIL
PLANTAA´
A
DESAGÜE
BORDILLO DE PROTECCIÓN
8.24
PALETS
1.20
LONA DE COBERTURA
15.67
4.09
2.19
8.24
5.85
PANEL SANDWICH DIVISORIO 6 CM
SECCIÓN A-A´
TAMBOR PARA ENROLLADO DE LONA
VENTILADOR CON REJILLA SEGURIDAD
TARIMA MÓVIL
BORDILLO PROTECCIÓN
BATERÍA FRIGORÍFICA
SOLERA H-20. 15 cm.
PRESOLERA H-10. 10 cm. PLANCHA POLIURETANO 5 CM
PANEL SANDWICH 10 CM
PANEL SANDWICH 8 CM
CONDITIONING, REDUCING SIZE
Handling and conditioning before cutting is usually accomplished in a‘dirty’ processing room, where temperature must be < 10ºC. It must be
completely separated from the ‘clean’ one in which the rest of operations will take place.
For peeling, manual and mechanical devices are used, being avoided • acids • alkalis • salts • high temperature • high pressure • freezing.
Cutting is mechanically practised with sharpened stainless steel knifesfor most products. As exceptions, carrot and potato need an abrasion
system and melon and watermelon a rotational punch.
To reduce the undesirable effects of peeling and cutting, the product temperature must remains under 4ºC.
The uneatable parts, commonly used for feeding purposes, should be immediately evacuated outside the factory by
• water • vacuum pumps.
WHASING Cut pieces are conducted to the ‘clean’ zone where the temperature must be under 10ºC. The access of workers to this area should be restricted and authorized only under strict hygiene.
Washing is the only step able to reduce the microbial loads. Cut pieces are actively washed and disinfected with GRAS coadjutants. They are usually dipped for 30 sec. to 3 min. into 50 to 150 ppm NaClO cold (1-5ºC) water and, eventually, with 250 to 300 ppm of ascorbic or citric acids for keeping pH at 6.5 to 7.5.
The use of O3 at 0.2 to 6 ppm in water or UV-C radiation is beingconsidered as an alternative to chlorine.
To optimize washing it is needed to use high quality water and generate turbulences by injecting high pressured air in the stainless steel washing tank. Also rotational drums or vibratory washers could be used.
Frequently the washing tanks incorporate filters to eliminate the insects remaining sometimes in the water washing surface.
WASHING - DISINFECTION- RINSING
RINSINGWashed pieces are actively rinsed with cold water at 1-2ºC, free from any additive (including chlorine) in a similar pool.
This pool should be provided of turbulences to separate the products (highly recommended in cut leafy vegetables) and supplement the advance system until the following stage. For dewatering, a discharge vibration sieve is commonly also provided.
The water consumption in both stages (washing and rinsing) is commonly about 6 to 12 l/kg of product.
In order to avoid off flavours, < 5 ppm of active chlorine must remain as residue in the product.
For saving water and energy consumption (≈30%) a continuous water filtering and recirculation system should be designed.
DRYING, MIXING
Rinsed pieces are dried in this same room by mean of semi-automatic or automatic centrifugation, being one of the most critical stages because very often lead to an increase in microbial load.
In USA, UK, Holland, Italy and Spain, drying by dry cold air or by infrared heating is being very recently applied on vegetable salads factories.
Cold dry air could be also obtained by injecting liquid N2 (about 125 g N2 / Kg product for lowering 13 ºC).
These innovations provide a better quality of products, although theyshow low efficiency and/or high cost.
If needed, the next stage is the mixture of varieties of dry product, manually made in a conveyor belt, like in some salads elaboration.
DRYING BY CENTRIFUGATION
VERTICAL CENTRIFUGATION SYSTEM
DRYING BY INFRARRED RAYS
DRYING BY HEAT AND COLD AIR
MIXING
ASSOCIATING, WEIGHTING, MAPAfter drying the use of the ‘clean room technology’ in a separate area
is strongly recommend. In the filtered air it should be assured less than • 70 particles with a diameter ≥ 5 μm/foot3
• 10.000 particles ≥ 0.5 μm/foot3.
The dry products are conducted to an automatic associated-weighed to supply the required quantities to a flow-pack machine provided with a hermetically heat sealing device
• vertical (for bags and bulks) • horizontal (for baskets and bowls).
A microprocessor settles down in each instant the right combination of some scale cells, to reach the programmed weight into the packages. The product contain in packages commonly varies from 250 g to 5-6 kg.
For products that hardly reach the optimum gas composition within packages by their respiratory activity, an active MAP system must be incorporated.
SALADS ASSOCIATING AND WEIGHTING IN A
VERTICAL FLOW-PACK
VERTICAL FLOW-PACK
HORIZONTAL FLOW-PACK
The films most commonly used for MFP are OPP and LDPE with appropriate thickness and permeability (often by micro-perforations)depending on the product.
For safety purpose it is absolutely critical that anaerobiose within packages will be avoided.
In particular cases (mainly for bulk leafy vegetables) and for a short duration until consumption packaging under partial vacuum are applied.
The limit date of safe consumption must be print on the package, being usually from 7 to 14 days.
WEIGHT, METALS AND QUALITY CONTROLS,PICKING AND PALLETIZING
All sealed packages are guided to the automatic weight-control and metals-detector.
Samples are picked up at random for quality control• physical • chemical • sensorial • microbial.
Throughout the commercial simulated shelf-life it should be monitored- gas composition within packages - microbial counts.
The microbial analysis are conducted in specialized laboratories. Because the product is shipped to the market very shortly, the time for having results is crucial if an alarm episode must be implemented.
Packages are placed in boxes, palletized and stored at 0/1ºC for ≤ 1 day.
Alternatively pallets are conducted to a picking area at 0/1ºC to preparethe commercial loads. Very commonly mixed pallets should be
supplied directly to retailers.
PICKING AREA
SHIPPING AND COMMERCIAL DISTRIBUTIONSubsequently pallets are conducted to the expedition area, refrigerated also at 0/1ºC, and designed to load directly the transport vehicles.
Shippers and truckers must contribute to keep right 0/1ºC product temperatures by
• cooling trailers before loading • recording the temperatures during loading and transportation• loading the pallets in order to ensure optimum air circulation• minimizing transit times.
The pallets are distributed to institutional consumers, companies of catering, restaurants or throughout nets wholesalers (logistic platforms or central markets) and retailers.
Concerning safety, the respect of the cold chain is of major importance. MFP products should be kept at 1 to 5ºC throughout the logistic, restoration establishments, retail sale exhibitors and even in the domestic refrigerators until consumption.
SHIPPING
SOME OTHERS DESIGNING CONSIDERATIONS
All the production areas should not have windows, they will have a suitable electric illumination, they must remain with the doors closed by means of automatic closings and with a low air overpressure to prevent contamination from the outside and it will be controlled the temperature, RH and the quality of the air.
It is also needed a good program of maintenance, cleaning, washing and disinfection (regular and in each product change) of all components of the processing lines, equipments and installations.
At least weekly, it should take place the cleaning and disinfection of all cold rooms including walls, roofs and floors, while the boxes, pallets, containers and tows should be washed and disinfected after each use.
Specific technical regulations for personal hygienic facilities and food contact surfaces also help in providing a higher overall produces quality.
EXEMPLE OF A SMALL FACTORY DESIGN< 10 t/day
EXEMPLE OF A MEDIUM SIZE FACTORY DESIGN20 to 40 t/day
1.- Receiving raw materials 2.- Raw materials cold rooms 3.- Processing rooms 4.- Processing line 5.- Gases tanks 6.- Processing controls7.- Cold storage and shipping 8.- Offices 9.- Quality control10.- Changing rooms 11.- Refrigeration equipment 12.- Auxiliary store13.- Repairing room
EXEMPLE OF A BIG FACTORY> 40 t /day
CÁMARA DEMATERIA PRIMA 1 ELABORADOS 2
CÁMARA DE
CÁMARA DE
10 ºC
2 ºC
NO REFRIGERADASALMACÉN MAT. PRIMAS
ÁREA DERECEPCIÓN
REFRIG.ANTECÁM.
CÁMARA DEMAT. PRIMA 2
POR AIRE FORZADOTÚNEL DE ENFRIAMIENTO
EXPEDICIÓNÁREA DE
ELABORADOS 1
destrío de tolva
SALA DE ENVASADO REFRIGERADASALA DE MANIPULACIÓN REFRIGERADA
DE ENVASESALMACÉN
línea evacuadora de desechos
12 ºC 12 ºC5ºC5ºC
5ºC
EXAMPLE OF A BIG FACTORY> 40 t/day
To implement, follow and audit GAP and GMP codesHandling raw materials separated from processed productsPhysical separation of dirty and clean areasApplication of sustainable unit operations under chilling temperatures
Following legal sanitation protocols HACCP systems and processing regulations in order to guaranty safety to consumers
• EU Directive 93/43/CEE • Spanish RD 3484/2000 • Codex Alimentarius
Packing: MAP, design, functionality and consumers demandRight shipping, transportation, distribution and retail sale under chilling.Traceability, quality control, product management and interaction with consumers.
SUMMARY Main Factors to be considered when Designing and
Operating Factories for Minimal Processing
REFERENCES
• Artés, F. 2000. Productos vegetales procesados en fresco. In: Aplicación del frío a los alimentos. Edit. Mundi Prensa. Madrid. Cap. 5:127-141. • Artés, F., Allende, A. 2005. Processing lines and alternative preservation techniques to prolong the shelf life of minimally fresh processed leafy vegetables. Eur. J. Hort. Sci. 70 (5) 231-245. • Artés, F., Artés-Hernández. F. 2000. Fundamentos y diseño de instalacionespara procesado en fresco de hortalizas. Alimentación, Equipos Tecnol. 3: 135-141.• Artés, F., Artés-Hernández. F. 2003. Principios y diseño de industrias de procesado en fresco de hortalizas. In: Envasado y comercialización de frutas y hortalizas mínimamente procesadas. Edit: Gobierno de La Rioja. Cap. V. 65-92. • Artés, F., Artés-Hernández. F. 2003. Etapas decisivas y diseño de instalaciones para la elaboración de productos procesados en fresco. In: Productos hortofrutícolas mínimamente procesados. Edit. Gobierno de Canarias. 57-78. • Artés, F., Artés-Hernández, F. 2003. Proyecto de Industria de procesado mínimo en fresco de hortalizas foliáceas. Promotor: Primaflor SAT. Unpublished. UPCT.
• Artés, F., Artés-Hernández, F. 2004. Designing industrial factories for minimal fresh processing of plant products. Inter. Conf. CIGR Bioproducts processing and food safety. Beiging. China. October. CD ROM.• Artés, F., Artés-Hernández, F. 2005. Proyecto de Industria de procesado mínimo en fresco de haba. Promotor: Frutas Esparza SL. Unpublished. UPCT. •Artés-Hernández. F., Artés, F. 2005. Concepción y ejecución de instalaciones industriales para el procesado mínimo en fresco de productos vegetales. In: Nuevas tecnologías de conservación de productos vegetales frescos cortados. Edit. CIAD-CYTED-CONACYT. Cap. 25. 456-472.• Food and Agriculture Organization and World Health Organization. 1997. CodexAlimentarius: Food hygiene basic texts. First Edit. Joint FAO/WHO Food Standards Program and the Codex Alimentarius Commission. Rome.• Fons, E., Graell, J., Latorre, J., Mothe, S., Ramo, T., Illa, J. 2002. Mejoras en las instalaciones frigoríficas y obra civil para reducir el consumo energético en almacenes de fruta. I Cong. Español Ciencias Técnicas Frío. Cartagena. 269-275. • Havet, M., Hennequin, F. 1999. Experimental characterization of the ambience in a food-processing clean room. J Food Engin. 39: 329-335• International Fresh-cut Produce Association. 2001. HACCP for the fresh-cut produce industry. Food safety guidelines for the fresh-cut industry. 4th Ed. Alexandria, Virginia, EEUU. Chaps. 1 and 8.
• Internacional Standard Oficial (ISO) 14644-1. 1999. Salas limpias y locales anexos. Parte 1: Clasificación de la limpieza del aire.• Real Decreto 3484. 2000. Normas de higiene para la elaboración, distribución y comercio de comidas preparadas. Boletín Oficial del Estado. Madrid. 1435-1441.• Sánchez, M.T. 2007. Cooling, storage and transportation. Temperature measurement and control through all the steps. European Fresh-cut Course. Bari . Italy.• U.S. Food and Drug Administration. 1998. Guide to minimize microbial food safety hazards for fresh foods and vegetables. U.S. Department of Health and Human Services. FDA. Center for Food Safety and Applied Nutrition. Washington D.C. 40 p.• U.S. Food and Drug Administration. 2001. Analysis and evaluation of preventive control measures for the control and reduction/elimination of microbial hazards on fresh and fresh-cut produce. U.S. Department of Health and Human Services. FDA. Center for Food Safety and Applied Nutrition. Washington D.C. Available at: http://www.cfsan.fda.gov/-comm/ift3-toc.html
