CAULIFLOWER POST HARVEST

1.0 Introduction

This training module will be used for training Field Staff (TOT), who will then train the farmers. The training will at both levels be interactive and will use live specimens for demonstration. The training will therefore be based near a farm or at least the trainees will be able to visit a farm of the produce at the period when harvesting and post-harvest handling are being carried out for practical demonstration.

Both quantitative and qualitative losses occur in horticultural commodities between harvest and consumption. Qualitative losses, such as those in edibility, nutritional quality, caloric value, and consumer acceptability of fresh produce, are much more difficult to assess than are quantitative losses. Quality standards, consumer preferences and purchasing power vary greatly across countries and cultures and these differences influence marketability and the magnitude of post-harvest losses.

This module therefore intends to help the horticulture smallholder farmers achieve the following:

To gain knowledge on and be able to recognize a mature cauliflower head for harvesting.
To gain knowledge and be able to practice harvesting of cauliflower heads.

To increase the farmers’ profitability through marketing of quality horticultural produce with minimized losses.

2.0 Pre-Harvest considerations

Cauliflower belongs to the cabbage, Brassica oleraceae family and therefore its harvesting and post-harvest characteristics are very akin to the head cabbage. Cauliflower (Brassica oleracea var. botrytis) is an herbaceous annual or biennial vegetable plant in the family Brassicaceae grown for its edible head. The head is actually a mass of abortive flowers (flowers which are unable to produce fruit or seed as they possess only female reproductive organs with the male organs either underdeveloped or totally lacking).

Cauliflower plants are shallow rooted with a small, thickened stem. The ribbed leaves branch off the top of the stem and are light green in color. The plant can reach a height of 1–1.5 m (3.3–4.9 ft) and it is most commonly grown as an annual crop, harvested between 60 and 100 days after planting. It’s popularity and high consumer demand stem from its nutritional quality and health benefits.

Cauliflower contains high levels of Vitamins C and B, calcium (Ca), Iron (Fe) and phosphorus (P) and is known to have health promoting benefits. Good quality cauliflower is sturdy and crisp with the curd void of brown spots and other discolorations. Good quality cauliflower must meet the following minimum quality specifications:

Compact, with a white head (curd)

Fresh and clean

Free from riciness

3.0 Harvesting

The cauliflower is harvested when the head is compact, white and firm at 15 – 20cm diameter. It is harvested manually by cutting the stem at the base of the head and leaving up to 4 leaves for protection. This is done when it has reached the desired curd size (which is a characteristic of the variety) and the right stage for its intended use so as to meet consumers’ demand for quality. In this case, as a vegetable cauliflower should be tender and crisp. Cauliflower curd exhibiting ‘riciness’ indicates over-maturity which does not meet the standard of quality.

Many crops are harvested very early in the morning to take advantage of the cool temperature. However, for cauliflower, the appropriate time to harvest is late morning to early afternoon. There is a need to allow the excessive moisture inside the curd to evaporate quickly (which occurs at higher atmospheric temperature) for the curd to be a little bit wilted or flaccid in order to minimize physical injury/damage during harvesting.

During manual harvesting, a cutting tool (such a scythe) is used to detach the cauliflower from curd. The curd should not be touched by the hand or by the cutting tool in order to minimize any physical damage to it. In many countries, the curd is harvested by cutting the stem with about 6 to 8 leaves still attached. The harvested curds are directly placed inside collection baskets with liners or in a plastic crate to be hauled to the collection center/area. The attached leaves protect the curd from physical damage during hauling.

4.0 Post-harvest handling

4.1 Cleaning

Once cauliflower is harvested, it’s usually recommended that you soak the head in salt water (2 tbsp to 1 gal) for about 20-30 minutes. This will help expel any cabbageworms that may be hiding inside the head. These pests will quickly come out and die so the head will not only be safe to eat but can be stored without worrying about having it feasted on. Cauliflower keeps best when frozen or canned but it will keep for up to a week or so in the refrigerator if wrapped in protective wrap. Chlorine or sulfur dioxide as metabisulphite can be incorporated into the cleaning water to effect disinfection of the produce at the same time.

4.2 Field Sorting

Field sorting of cauliflower curds should be done on farm to cull out unmarketable curds such as those that are diseased, insect-infested or rat-damaged. Performing this operation in the field will also minimize hauling costs. Sorting also removes heads that are separated and not well compacted.

4.3 Trimming

The field sorted cauliflower curds that reach the pack-house or collection center should be trimmed of excessively long stems as well as the leaves that are still attached to the stem. Based on the set Cauliflower Standard “the cauliflower head or curd should be well trimmed with a 10 mm stem and a maximum of four wrapper leaves”. Based on studies, the attached leaves are the ones that deteriorate first during marketing and storage. This enhances deterioration of the curd as well, since the curd is very sensitive to the ethylene that is evolved by the senescing /deteriorating leaves.

4.4 Sorting and grading

Cauliflower curds should be sorted and classified based on certain standards of quality. The quality standard may be institutionalized nationally or established by a private sector entity. Cauliflower curds may be classified as: either Premium Grade, Grade 1 or Grade 2. Sorting and grading must be done in a packing area equipped with sorting tables, weighing scales or a sorting device. Grading must be done in a location that is well-lit. The work place must be compliant for the safety and welfare of the sorters/classifiers.

4.5 Packing

Bulk packaging is probably one of the weakest links in the cauliflower post-harvest chain. Losses and quality defects that result from inappropriate use of bulk packaging materials include: bruising, wounding (cut, puncture, crack, split, breakage), distortion, compression damage and abrasion. The extent of this damage increases when the packages are either under-filled, over-filled or if the packaging material has rough surfaces, and when the packages are dropped during handling.

The packaging materials commercially available in Nepal for use in handling and transporting fresh produce like cauliflower include: bamboo baskets or ‘duko’, wooden crate, returnable and stackable plastic crates, polyethylene or polypropylene plastic bags, sacks made from plastic twine, and cardboard box/cartons. With the exception of plastic crates, these packaging materials are commonly used because of their low cost and widespread availability, but in most cases, they are used inappropriately (through overfilling and incompatibility with the nature of produce) especially in hauling and in transporting fresh produce from the farm.

Although the plastic crate is the packaging material that is most cost-effective (due to the long time over which it can be used) and the high level of protection against mechanical damage, it is not popular and is not commonly used because of its high cost. Carton boxes are mainly for export but used carton boxes find their way in the packaging fresh produce for local marketing. Used carton boxes have very low resistance to compressive load, thus, compression damage is high in this kind of packaging material.

Based on studies, the best container for cauliflower curds is the plastic crate because of its smooth inside finish, ease of cleaning and the fact that it can be used over a long period (10 years maximum). For best results, the layers of curds inside the plastic crate should be lined with plastic sheet liners so as to minimize abrasion damage to the curds during transit. When using plastic crates as container, the following considerations should be borne in mind:

Hygiene – plastic crates should be thoroughly cleaned with soap/detergent and then sanitized by dipping them in a sanitizer such as sodium hypochlorite to reduce the microbial load on the crate.

Handling – handled with care during loading, stacking and unloading; do not drop. Do not use as seats when sorting.

Storage – stored in a clean area that will prevent insects and rodents harboring the crate or storage area. Store the crates separately from chemicals and farm machinery to prevent contamination. Crates should not be left exposed to the external environment since they will readily wear out. Do not use as a storage or transport container for chemicals (fertilizers and pesticides).

4.6 Transport and Market Handling

Transport is key in the distribution of fruits and vegetables. Because of their inherent perishable nature, fruits and vegetables must reach the destination market in a short period of time, necessitating rapid and reliable transport systems. These include transport systems that are used to haul cauliflower from farm to collection center, from collection center to wholesale market and to retail markets. Losses incurred during transport are a complex problem not only directly related to the transport vehicle, but also affected by the length of the trip, number of loading and unloading points, road quality, temperature of the environment and availability of handling aids. For the cauliflower curds to arrive at their destination in good condition, proper transport practices should be observed:

Handle containers of produce gently during loading and unloading; they should not be dropped or thrown on to each other to avoid physical damage.

Do not use containers that allow compaction of the produce during loading into the track or transport means

Cover the packages to avoid exposing them to the heat from the sun.

Allow air to circulate in the stacks or piles of produce by providing space in between stacks. If canvass is used as cover, provide space for air to pass through at the bottom and top of stack; use light colored material as cover as this will reflect heat.

Ensure that the transport vehicle is cleaned and disinfected before loading:

Cauliflower is usually marketed by farmers or traders in wholesale and retail markets. Upon arrival at these distribution channels, certain basic rules should be followed to maintain the freshness and quality of the curds:

Containers must be carefully unloaded from the transport vehicle to the marketing area or under a shaded area.

Depending on the target market or buyer, re-sort or re-grade the curds and discard culls properly.

Do not place the packages of cauliflower curds in dirty areas in the wholesale market to minimize microbial contamination.

In the retail market, cauliflower curds are best sold in retail packs since this prevents damage due to frequent handling by customers when they select the curds. If the curds are not packaged in retail packs (exposed), they should be displayed in a place that is well protected from the sun and other hazardous contaminants.

5.0 Causes and controls for post-harvest loss in Cauliflower

Loss of water leading to wilt/shrivel of the heads and the protective leaves - keep in cool or cold place with high relative humidity (>80%) and packaging in closed packs

Microbial damage leading to decay - disinfect with chlorinated water or water containing Sulphur dioxide (500 – 600 ppm chlorine and 300 – 500 ppm of sodium/potassium metabisulfite.

Physical injury during harvesting, handling or transportation opening way to other routes of spoilage - care in harvesting, handling and transportation.

6.0 Post-Harvest diseases & Pests

I.Black spotting / curd blackening

This is a major postharvest disorder that affects cauliflower. The causes are not well understood, but they could be microbial, physiological, or both. Low temperatures, avoiding free moisture on the curds and careful handling reduce curd blackening.

Figure 1 Curd blackening in Cauliflower

II.Downy mildew Hyaloperonospora parasitica

Caused by fungus and displays small angular lesions on upper surface of leaves which enlarge into orange or yellow necrotic patches; white fluffy growth on undersides of leaves. Disease emergence is favored by cool, moist conditions and can be managed by removing all crop debris after harvest. Rotation with non-brassicasit is possible to control downy mildew with the application of an appropriate fungicide.

Figure 2 Cauliflower with downy mildew

III. Leaf spot/target spot (Alternaria species)

Two closely related species of the Alternaria fungus (A. brassicae and A. brassicicola) cause this disease. The circular leaf spots vary from mid to dark brown to black. The spots often have a target-like appearance as a yellow halo surrounds the sunken centre. As well as affecting the leaf, the disease can cause blackening of cauliﬂower curds. The disease occurs when conditions are moist. The fungus can be carried over on crop residues and brassica weeds.

Figure 3 Leaf spot on cauliflower

7.0 Evaluation of the training

The trainer, in a plenary during training of farmers, can do this evaluation as a quick written test during training of field staff and as guided discussion of the answers to the questions. It is meant to assess the extent of learning

Describe the maturity of cauliflower at harvesting.
Describe the appropriate method of harvesting cauliflower.
Explain sorting of cauliflower after harvesting.
Enumerate the deteriorative/spoilage factors of cauliflower during storage.
Describe cooling and disinfection of cauliflower.
Describe the appropriate packing, transportation and storage of cauliflower.