VALUE ADDITION AND FOOD SAFETY FOR FRENCH BEANS

Introduction

3.1 Background information

French Beans are the immature green pods of Phaseolus vulgaris and are also referred to as Green Beans or Snap Beans. French beans belong to the Fabaceae family in which other members include: the common bean, pulses and peas. They are specifically bred and cultivated for their pods versus their seeds. They are mainly produced for export and the main markets are the United Kingdom, France, Germany, Holland and Belgium. The beans are grown by both large scale and smallholder farmers in Rwanda. Staggered planting in small lots is recommended as it is labour intensive. The beans are grown for both fresh consumption as well as processing, mainly canning and freezing. Young French bean pods may be prepared whole then eaten raw, or lightly steamed or sautéed. French beans are also used in salads or prepared with other vegetables, herbs as well as some nuts and dried berries. The French beans have a nutrient content of Vitamin A and C both of which are key in maintaining a good health and nutrition status and preventing deficiencies.

Varieties of French beans grown in Rwanda include: Samantha, Argus and Ferali. French beans have a short harvesting period of less than two months. These offers high yield outputs which are mainly targeted for export and thus offer a great source of economic importance within the French bean value chain. In Africa the harvesting of French beans is mainly done by hand. This gives higher yields and better quality than mechanical harvesting which also requires costly machinery. French beans are harvested once they reach a length of between three to four inches which is when their texture and flavour is at its peak. French beans are cylindrical in shape yet thin and with an outline along the contour of the pod as a result of the peas shelled tightly inside the pod.

 

3.2 Postharvest handling of French beans

1. Sorting:  It involves the removal of undesirable pods (immature, over-matured, broken and diseased). The beans must be whole, unbroken, complete, of fresh appearance, clean and free from excess external moisture. Those beans with physical injuries and blemishes are removed (Figure 3.1). They must be of the specified size to satisfy market requirements and specifications (El-Mogy & Kitinoja, 2019).

Figure 3.1: Sorting of French beans

2. Grading: There are three main grades of French beans namely; extra fine, fine and bobby. For the extra fine grade the pods are straight, tender in texture and seedless with no strings and with a pod diameter of less than 6 mm and minimum length of 10 cm. In fine grade the pods are short with soft string and small seeds with a pod diameter of between 6 – 9 mm and length of 12 – 14 cm. Bobby Grade has pods that are bigger in size than fine grade and are relatively tender with small seeds that have a diameter of more than 9 mm.

3. Pre cooling: French beans are stored at temperatures of between 7 to 8℃ and a relative humidity of 95 – 100 % for a period of 1 – 2 weeks to prevent spoiling.

4. Packaging: Packing of French beans affects their pod quality. The selection of a suitable packaging material reduces weight loss and decay. French beans can be packaged in various types of containers, depending on the market and consumer demands. The preferred containers are fibreboard boxes and perforated polyethylene bags (El-Mogy & Kitinoja, 2019).

Figure 3.2: Packaged French beans

5. Refrigerated storage: Storage temperature of French beans after harvest and during handling significantly affects the quality of green bean pods especially visual qualities such as appearance, colour, freshness and nutritional content of pods. The ideal refrigerated storage conditions for French bean pods is 5 - 7 °C and 95-100 % relative humidity (Cantwell and Suslow, 2010). These conditions extends the shelf life of the  pods to 12 days with an acceptable appearance (El-Mogy & Kitinoja, 2019).

3.3 Pre-treatments before processing

1. Cleaning of French beans

This is done by following three steps:

• Sort the beans to remove damaged, mouldy and diseased beans as well as those with impurities.
• The bean pods are then soaked in clean water to loosen the dirt on the surface.
• The pods are then placed in a colander and washed over running water thoroughly. Use hands to rub the beans to ensure even washing.

2. Trimming (Removal of inedible portion)

After cleaning, the pods are trimmed off the stem and tail ends. If the pods have fibrous surfaces, they are removed.

 

 

4. Principles of Preservation and Value addition

4.1 Preservation by Freezing

This is achieved through the following steps:

1. Washing of the French beans and removing the ends- Wash the beans over cold running water thoroughly, trim off the stem and tail ends of the French beans. If the French bean variety has a tough fibre on the bean pod, trim them off.
2. Size reduction (optional) - Cut the beans into small pieces of the desired size commonly 1-2 inch pieces. Although this step is optional it depends on the intended use of the beans

1. Blanching the French beans- Blanching is a short heat treatment commonly applied to tissue systems prior to canning in order to firm their texture by settling of the calcium pectate along the cell walls. Using a large water pot, boil water and dip the bean pods or use a blancher for 2-4 minutes. On the boiling water, add salt to ensure a firm texture. Transfer the blanched bean pods into ice to stop cooking and avoid sogginess and preserve the green colour.
2. Freezing the bean pods- Arrange the beans in a single layer on a baking sheet and freeze until firm. This ensures that the pods do not cling together during the frozen storage (pre-freezing). Pack into freezer bags, jars or containers, press to compact them to ensure no air is incorporated, tight seal and freeze them (Schenck, 2007).

Figure 4.1: Washing French beans

 

Figure 4.2: Blanching French beans

      

Figure 4.3: Pre-freezing of pods before packing

Figure 4.4: Packaged pods for frozen storage

Figure 4.5: Frozen French beans

 

4.2 Preservation by Canning

Canning and preserving green beans which are low-acid foods (pH above 4.5) involves pressure canning to eliminate microorganisms that cause food poisoning if consumed with food. Pressure canning at 240 degrees kills spores which are the most resistant to heat with and the main target spore former is Clostridium botulinum. Under low oxygen conditions, Clostridium botulinum produces a dangerous neurotoxin called botulinum toxin. The toxin can cause progressive paralysis due to its toxicity to the nervous system and if not managed promptly can lead to death.

4.2.1 Basic steps in canning

Production of a commercially sterile food in a container follows the following steps, illustrated using conventional canning:

1. Preparatory processes
2. Container filling, exhaustion and closure
3. Retorting or cooking to achieve sterility
4. Cooling

1. Preparatory processes

This includes: sorting, cleaning (wet or dry), size reduction and grading. The most important preparatory process in canning is blanching – done for most vegetables and only a few fruits. Blanching is aimed at inactivating enzymes for the short time between cutting and filling into containers, and firming the texture (already ben explained). In a small operation, most of these processes are manual, in a large operation they are mechanized.

1. Container filling, exhaustion and closure

French beans are filled in containers with brine (salt in water may be with small quantities of glucose – for flavour). In some vegetables small quantities of calcium salt may be added. The brine is always drained prior to consumption. Container exhaustion (evacuation) can be done by filling with hot liquor to displace the air (air solubility is low at high temperatures) or mechanically using of a vacuum pump. Container closure can be done mechanically or manually.

1. Cooking and retorting to achieve commercial sterility

Cooking/retorting is done to achieve commercial sterility. French beans, being low acid foods, are given a severe heat treatment to achieve commercial sterility. Temperatures higher than normal boiling water are used (most commonly 121^oC/250^oF). These temperatures are achieved by operating the retort at 2 atmospheric pressure in the head of the containers (see your pressure cooker). The heating medium of the containers is either water or steam, but the heating medium of the food is the brine.

1. Cooling

The cooling is always done with cold water. The introduction of water has to be well balanced to avoid breakage of the container due to high external pressure generated

Figure 4.6: Canned French beans

4.3 Preservation by Dehydration (Drying)

Preservation by drying is achieved by performing the following steps:

1. Washing - Wash the top and tail and string of the French beans
2. Size reduction- Young beans can be dried whole but older beans need to be cut into strips.
3. Blanching- French beans are blanched in boiling water for about 3 minutes and then fully drained. Colour retention can be enhanced by adding ½ or (14 g) of bicarbonate of soda to each gallon (4.5 litres) of the blanching water but this does destroys some of the Vitamin C content.
4. Drying - Spread the beans onto trays and dry at a temperature starting at 50°C/120°F and then increase the temperature slowly up to 70°C/150°F. Sun drying can also be used. Depending on the size of the beans, drying takes between 2-3 hours. The final moisture content should be 14% (Doymaz, 2005)
5. Packing - Pack in tightly corked bottles or airtight containers and store in a dark dry place.

Before consumption, the French beans are soaked in cold water for about 12 hours or until they are soft.

   

Figure 4.7: Dried French beans

4.4 Preservation by pickling process

Pickling is a method of preservation and value addition which involves preserving foodstuffs under high acid concentrations (adding vinegar and salt). It allows water bathing canning of vegetables that would otherwise require pressure canning. Safe water bath canning needs a pH below 4.6 (Behera, Farag, & Sheikha, 2020).

The pickling process involves the following series of steps:

1. Snap the French beans ends, and remove strings as necessary. Discard any discoloured, soft, or otherwise faulty beans.

2.      Make pickling brine by combining salt, vinegar and water in a large stockpot. Bring to a boil.

3.      Pack beans lengthwise into hot jars, leaving 1/4 inch headspace. Pour the hot brine over beans, leaving 1/4 inch headspace. Remove air bubbles with a wooden chopstick

4.      Place jars in a water bath at 82°C/180°F prior to sealing in order to sterilize them for 25-30 minutes. See below.

Figure 4.8: Water bath canning

 

5. Introduction to Product Quality Assurance       

5.1 Food safety and Standards applied

Food safety is the assurance that food will not cause harm to the consumer if handled and prepared as per the intended use. Food safety includes handling practices like preparation, packaging, storage and transportation.

Food safety concerns by consumers in the European Union (EU) because of food contamination by microorganisms and pesticides have led European governments to enact stringent food safety regulations. The EU fresh produce retailers, especially supermarkets, have responded to consumer concerns and these regulatory changes by developing their own protocols and passing them upstream to developing-country exporters. These private protocols are often more stringent than official regulatory requirements. To secure their markets in the EU, exporters in developing countries have, in turn, responded to the international food safety standards (IFSS) by imposing very strict requirements on farmers and fresh produce suppliers. These requirements include: i) pesticide use and handling standards, ii) establishment of traceability systems and, iii) hygiene standards.

5.2 Types of food safety standards

Food safety standards may be of various types:

• numerical standards defining required characteristics of products, such as contaminant limits or maximum residue limits (including methods of sampling and analysis to be applied in the measurement of the specified characteristic)
• process standards that define how the food should be produced including verifiable performance objectives which may be numerical
• Process standards that define the requirements of the management system such as documentation requirements.

5.3 International food safety standards

With the introduction and enforcement of IFSS, leading exporters in developing countries that supply developed-country supermarkets and/or EU countries that demand IFSS compliance have moved into more closely governed contracts as compared to the previous loose contracts. These new contracts require farmers to comply with IFSS.

 

IFSS-compliant French beans have to meet specific production and farm-level postharvest handling requirements, namely: i) spray operators wear full protective gear, ii) pesticides are handled in ways that ensure safety to mixers and applicators, iii) pesticide applicators bathe immediately after spraying or when pesticides accidentally come into contact with the skin, iv) pesticides are stored away from foodstuffs in a fully secured pesticide store with adequate ventilation, v) disposal of pesticide containers and leftover pesticides is done in ways that do not threaten the health of humans or animals and vi) farmers discontinue the use of unapproved pesticides and ensure that residues of approved pesticides on the harvested beans remain below the maximum residue level (MRL). In addition, green beans are required to meet a number of postharvest handling requirements. In particular, grading must minimize contamination by microbes or foreign objects (e.g., dirt and human hair) and shield the beans from the tropical heat. Lastly, each farmer is required to document pesticide use practices for each plot of beans. The record of pesticide usage accompanies each consignment of green beans sold.

 

In order to become IFSS-compliant, a farmer needs to change a number of production practices and make significant investments including the following: i) purchase protective gear, including long-sleeved overalls, gumboots, rubber gloves, nose mask, goggles, and hat; ii) construct a shower room for use by the spray operators, a well-ventilated and secured pesticides store, a pesticide disposal pit and an incinerator; iii) apply only approved pesticides typically more costly but safer than those they replace; iv) implement an integrated approach to managing pest and disease problems, and only use pesticides when absolutely necessary (i.e., upon approval by the exporter’s agronomist or technical assistant); v) construct a grading shed (with cement floor, washable tables, and facility for washing hands) and a pit latrine adjacent to the shed; vi) build a charcoal cooler for holding graded beans prior to pick up by exporter; vii) observe personal hygiene at all times during grading of green beans. The hygiene measures taken include the use of headscarves by women and hats by men, barring children from the grading area, and barring the wearing of perfumes from sorting and grading areas.

 

Other international standards that need to be observed in the French bean value chain include:

• World Trade Organisation (WTO) - the WTO provides a set of rules for multilateral trade, and is a forum to resolve disputes and negotiate new rules. Since standards are essential for smooth trade, the WTO Agreements strongly encourage governments to harmonize their requirements on the basis of international standards (CODEX Alimentarius, 1997; FAO, 2017)
• HACCP- (Hazard Analysis and Critical Control Point). Usually, HACCP is a process standard that consists of an internal team identifying critical control points throughout the process (Vieira, 2006) with aim of controlling hazards in foods
• Good manufacturing practices (GMP) - is a system for ensuring that products are consistently produced and controlled according to quality standards. It is designed to minimize the risks involved in any pharmaceutical production that cannot be eliminated through testing the final product.
• Good Hygienic practices (GHP)- covers the minimum sanitary and hygiene practices for food processors, such as hotels and restaurants, to ensure that food is safe and suitable for human consumption. It is a required foundation to implement other food safety management initiatives, such as GMP, HACCP and ISO 22000.
• ISO standards- are internationally standards by International Standards Organization outlining the requirements for making a product, managing a process, delivering a service or supplying materials and a huge range of activities.

5.4 Basic Characteristics of a Standard

• Unambiguous, testable (verifiable), clear (concise, terse, simple, precise
• provide a high level of health protection
• Have clear definitions to increase consistency and legal security
• Should be based on high quality, transparent, and independent scientific advice following risk assessment, risk management and risk communication;
• Include provisions for the right of consumers to have access to accurate and sufficient information;
• Provide for tracing of food products and for their recall in case of problems
• Include obligation to ensure that only safe and fairly presented food is placed on the market;
• It should also recognize the country's international obligations particularly in relation to trade

5.5 Importance of Standards

• Maintaining potentially hazardous food at correct temperatures- to limit growth of food poisoning bacteria, the food is kept at temperature of between 5℃ and 60℃
• Cooking or another processing step to make food safe-temperature specifications ensure that cooking is done correctly
•  Protecting food from contamination- the specifications ensure that food is free from contamination
• Food disposal-returned foods are disposed-off effectively
• Food recall-ensures product recall is documented

Source: (Swami, 2013)

 

 

6. Product Traceability   

Traceability’ means the ability to trace and follow a food, feed, food producing animal or substance intended to be, or expected to be used for these products at all of the stages of production,  processing and distribution.

Traceability is the ability to maintain a credible custody of identification for food products through various steps within the food chain from the farm to the retailer (CODEX, 2002). The traceability is a key factor for imposing food safety standards. An effective and economically sound tracing system should identify specific areas, where the problems stem from (Savov & Kouzmanov, 2014).

Internal traceability -Traceability between the received unit (or raw material unit) and the sold unit (or product unit) at the food operator level

One-step-back traceability- Ability to identify the supplier of the units they have received  If the material flow and the business flow differ, we will follow the material flow and call the one-step-back operator as “supplier”.

One-step-forward traceability -Ability to identify the buyer of the units they have sold If the material flow and the business flow differ, we will follow the material flow and call the one-step-forward operator as “buyer”

Chain traceability- Traceability throughout the food chain

6.1 Components of a traceability system

Traceability system -A series of mechanisms for traceability, by which “identification”, “link”, “records of information”, “collection and storage of information”, and “verification” are performed (Food Marketing Research and Information Center (FMRIC), 2008)

6.1.1 A mechanism for identifying Traceability Resource Units (TRUs)

When choosing how to identify TRUs, we have to choose the identifier code type and structure. Choices have be made with respect to granularity and uniqueness of the code, and associate the identifier with the TRU (Olsen & Borit, 2018).

6.1.2 A mechanism for documenting transformations

Once the type of identifier to use is selected and has been associated to the TRU, documentation of what happens to the TRU as it moves through the supply chain needs to be done. The supply chain for food products is often long and complex, and TRUs do not necessarily last long; they are constantly split up, or joined together with other TRUs. These splits and joins are referred to as transformations, and the ability to document the sequence of transformations is one of the most important functions of the traceability system (Dillon & Derrick, 2004; Olsen & Aschan, 2010).

6.1.3 A mechanism for recording TRU attributes

Once we have selected what type of identifier to use, and we have found a way to associate the identifier to the TRU, we have the ability to record attributes associated with the TRU in  question, and to link these attributes to the TRU identifier (Olsen & Borit, 2018).

 

 

7. Equipment / processor Maintenance and Operation 

 Figure 7.1: A large scale French bean canning line

Large Scale Vegetable Canning Equipment For Green Beans Processing Line

Figure 7.3: French bean processing line

7.1 Preventive Maintenance

Preventive maintenance can be defined as follows: Actions performed on a time- or machine-run-based schedule that detect, preclude, or mitigate degradation of a component or system with the aim of sustaining or extending its useful life through controlling degradation to an acceptable level.

Advantages

• Cost effective in many capital intensive processes.
• Flexibility allows for the adjustment of maintenance periodicity.
• Increased component life cycle.
• Energy savings.
• Reduced equipment or process failure.
•  Estimated 12% to 18% cost savings over reactive maintenance program.

Disadvantages

• Catastrophic failures still likely to occur.
• Labour intensive.
• Includes performance of unneeded maintenance.
• Potential for incidental damage to components in conducting unneeded maintenance.

          

7.2 Predictive maintenance

Predictive maintenance can be defined as follows: Measurements that detect the onset of a degradation mechanism, thereby allowing casual stressors to be eliminated or controlled prior to any significant deterioration in the component physical state. Results indicate current and future functional capability (Sullivan et al., 2002).

Advantages

• Increased component operational life/availability.
• Allows for pre-emptive corrective actions.
• Decrease in equipment or process downtime.
• Decrease in costs for parts and labour.
• Better product quality.
• Improved worker and environmental safety.
• Improved worker moral.
• Energy savings.
• Estimated 8% to 12% cost savings over predictive maintenance program.

Disadvantages

• Increased investment in diagnostic equipment.
• Increased investment in staff training.
• Savings potential not readily seen by management.

7.3 Corrective Maintenance

Corrective maintenance is defined as actions carried. It is one that occurs after the identification and diagnosis of a problem. It is maintenance identified by a condition monitoring system or due to breakdown. Corrective maintenance, as a subset of comprehensive preventive maintenance focuses on planned activities that maintain all parts of machinery and systems in best possible working form. The major aim of corrective maintenance is that repairs are carried out properly and completely on all emerging problems on a need basis. Also that the repairs are carried out by well-trained craftsmen and confirmed before the machine is returned to operation (Otieno, 2016)

The major weakness of corrective maintenance is that there is unscheduled machine downtime and maintenance cannot be pre-planned. If a machine part fails and the spare parts are not maintained by the firm or are not readily available delays occur between the ordering and delivery causing delays in production.

 

 

8. Conclusion

French beans are vegetables with short maturity time and highly perishable making it have a very short shelf life. In Rwanda, farmers experience high post-harvest losses if the market for fresh ones is not available. There is need to exploit the available preservation and value addition technologies to increase income for farmers and processors.

 

 

9. References

Behera, S. S., Farag, A., & Sheikha, E. (2020). Traditionally fermented pickles : How the microbial diversity associated with their nutritional and health bene fi ts ? Journal of Functional Foods, 70(December 2019), 103971. https://doi.org/10.1016/j.jff.2020.103971

CODEX Alimentarius. (1997). Codex Alimentarius : food quality and safety standards for international trade. 16(2), 313–321.

Doymaz, I. (2005). Drying behaviour of green beans. 69, 161–165. https://doi.org/10.1016/j.jfoodeng.2004.08.009

El-Mogy, M. M., & Kitinoja, L. (2019). Review of best postharvest practices for fresh market green beans. (February).

FAO. (2017). Trade and food standards.

Food Marketing Research and Information Center (FMRIC). (2008). Handbook for Introduction of Food Traceability Systems.

Maurine, O. (2016). CORRECTIVE MAINTENANCE PRACTICES AND OPERATIONAL. (November).

Olsen, P., & Borit, M. (2018). SC. Trends in Food Science & Technology. https://doi.org/10.1016/j.tifs.2018.05.004

Savov, A. V, & Kouzmanov, G. B. (2014). Food Quality and Safety Standards at a Glance. 2818(2009). https://doi.org/10.2478/V10133-009-0012-8

Schenck, R. (2007). Canning Green Beans Ecoprofile of Truitt Brothers Process.

Sullivan, G. P., & Pugh, R.Melendez, A. P.Hunt, W. D. (2002). Operations & Maintenance.

Swami, C. (2013). FACULTY OF BIOSCIENCE ENGINEERING Importance of food safety and quality standards at various levels in the tomato supply chain of South Africa. 1–78.

Vieira, L. M. (2006). The Role of Food Standards in International Trade : Assessing the Brazilian Beef Chain. (September 2005), 17–30.