Post-harvest guidelines

POST-HARVEST GUIDELINES

This document is intended to be a user friendly operational guide addressed to the hazelnut growers.

Special thanks are due to Dr. Nadia Valentini who gave a professional contribution to the development of this Guideline.

Ferrero Group waives any responsibility in respect to the completeness and accuracy of the content of this operational guide which in no case is to be considered as a binding document for the hazelnut growers.

Copyright Reserved - Disclosure of this document is not permitted unless expressly authorized by the Ferrero Group

INDEX 1. QUALITATIVE CHARACTERISTICS OF HAZELNUTS

4

3.

CLEANING AND DRYING OF HAZELNUT

16

1.1

Chemical composition of hazelnut

5

3.1.

Cleaning hazelnut

17

1.2

Seed alterations during storage

6

3.1.1.

Dry cleaning system

18

3.1.2.

Water cleaning system

19

2. NUTS PROCESSING AFTER HARVEST UNTIL STORAGE

7

2.1.

Delivery to processing facility and sampling

8

2.2.

Quality parameters, randiman and quality grade determination

10

2.2.1.

Quality parameters

10

2.2.2.

Laboratory equipment for quality analysis of hazelnut

11

Randiman determination

13

2.2.3.1.

13

2.2.3.

Determination of visible defects (rotten and shrivelled nuts)

Determination of quality grade

13

2.2.4.1.

14

2.2.4.2. Determination of the hidden defects

2.2.4.

2.3.

Determination of visible defects (corken damages)

Other quality parameters

3.2.

Drying hazelnut

19

3.2.1.

Natural drying

20

3.2.2 .

Artificial drying

20

4.

PACKAGING AND STORAGE

23

4.1.

Types of packaging (pros and cons)

24

4.2.

In-shell hazelnuts storage

24

4.2.1. Nuts storage in farm

24

4.2.2. Nuts storage in processing facility

26

CALIBRATION AND SHELLING NUTS

27

14 15

5.

REFERENCE LIST

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POST-HARVEST GUIDELINES

QUALITATIVE CHARACTERISTICS OF HAZELNUTS

1.1.

Chemical composition of hazelnut

Dried fruit has beneficial properties on human health that derive from its composition particularly rich in plant lipids and bioactive substances. These same substances allow the hazelnut a good shelf life, if the most appropriate and correct post-harvest management techniques are applied.

After drying, the seed has a moisture content of about 6%. The total oil content of the hazelnuts ranges from 58 to 65% on fresh weight, while the protein ranges from 8 to 15% (table 1.1). Hazelnuts also contain significant quantities of dietary fibers, mineral elements, and vitamins (table 1.2). Hazelnuts are an excellent natural source of the antioxidant vitamin E due to their tocopherol content, and are also rich in other biologically active compounds such as polyphenols.

Lipids have a fatty acid composition similar to that of olive oil, with 77-83% of oleic acid, 7-14% of linoleic acid, 5-7% of palmitic acid, 2-3% of stearic acid, with small quantities (<0.2%) of palmitoleic, linolenic and arachic acids. The propensity of the cultivars to rancidity of the oil is correlated to the percentage of linoleic acid which is a polyunsaturated fatty acid.

Hazelnuts are one of the most nutritious nuts that contain valuable amounts of nutrients, among which lipids predominate. The particular fatty acid composition, rich in monounsaturated fatty acids, has a recognized beneficial effect on human health. However, due to their high lipids content, hazelnuts are easily susceptible to rancidity. The aim of the post-harvest processing is to minimize metabolism, fungal, oxidative and enzymatic activity in the seed thanks to timely drying and proper storing: this, not only has fundamental impact on the quality of the crop but is of utmost importance for avoiding development of aflatoxins which could endanger human healthy.

Table 1.1 Main compounds in raw hazelnut seeds

Compounds

On fresh weight %

Water

5-6

Oleic acid (77-83%), Linoleic acid (7-14%),

Total oil content (lipids)

58-65

Palmitic acid (5-7%), Stearic acid (2-3%)

Total protein

8-15

Arginine, Glutamic acid, Aspartic acid

Fiber

10-13

Sugars

3-5

Ashes

2.2-2.5

Sucrose (90%)

Table 1.2 Other compounds in raw hazelnut seeds

Phytosterols

β-sitosterol (90-130g/100 g of oil)

Vitamins

B1, B2, B3, B6 (0.4-0.6 mg/100 g), E (α-tocopherols 25-50 mg/100 g of oil)

Mineral elements

K (500-800 mg/100 g), Ca (250-400 mg/100 g), P (200-400 mg/100 g), Mg (150-200 mg/100 g), Fe, Zn, Cu, Mg, Se

Phenolics

Flavonoids (20-40 mg GAE/100 g) 5

POST-HARVEST GUIDELINES

1.2.

Seed alterations during storage

The main alterations that can occur during storage are due to lipids. The lipids consist of triglycerides which can release fatty acids during storage causing the product to become sour (acidification). The acidity upon harvesting is normally less than 0.1 g of oleic acid per 100 g of oil and gradually increases during storage; it is 1.5-2 times higher in roasted seeds than in raw ones.

The high presence of unsaturated fatty acids, can give rise to rancidity, a condition produced by oxidation of unsaturated fat with degradation of the molecule and formation of aldehydes (hexanal) and oxyacids, unpleasant at a sensorial level. The evaluation of the oxidation state of the lipids is given by the measurement of the peroxide content which is normally lower than 0.2 mEqO2 / kg of oil in the seed at harvest. Also in this case, roasting determines an increase in the peroxide content which, during storage, grows even more rapidly than is observed for acidity. There are no limits set by the legislation for the two parameters but it is preferable that in raw hazelnuts the acidity does not exceed 0.4% and the peroxide content of 0.5 mEqO2 / kg. Another variation that can occur during storage concerns the color of the perisperm which tends to darken due to the oxidation of phenolic compounds. In any case, if storage is not properly done, rotten issues and aflatoxins can easily seriously increase the damage to the quality of the lots.

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NUTS PROCESSING AFTER HARVEST UNTIL STORAGE The operations that follow the hazelnut harvest in the field are related to cleaning, drying and storage of in-shell nuts (Fig. 2.1). These operations can be performed directly by the farmer who has proper equipment to carry out the process, or by a processing facility; in this case the crop has to be delivered by the farmer as soon as possible after the harvest. The processing companies will be in charge of the operations of quality assessment, storage and shipment to the facilities for further processing.

POST-HARVEST GUIDELINES

POST-HARVEST GUIDELINES

Farm HARVEST

CLEANING

Processing facility SAMPLING FOR QUALITY CHECK

DELIVERY TO PROCESSING FACILITY

CLEANING & DRYING

QUALITY ANALISYS

DRYING

The gross quantity of hazelnuts delivered to the facility is recorded by weighing the means of transport (truck, trailer, etc.) with a truck scale, before and after the delivery of the product (Fig. 2.5). Specific scales automatically record the weight and there is no need for any calculation by the operator. In case the farmer delivers more than one variety, it is of utmost importance that each variety is delivered separately and not mixed with any other.

Figure 2.5. Trailer and tractor are weighed before and after the delivery of the product on an automatic truck scale (Photo by Agriserbia)

When arrived at the processing facility, the first step is the sampling of the product for carrying out the qualitative analysis.

The lot is sampled in different points by a special probe (manual, automatic or semi-automatic) exploring the entire profile of the trailer (Fig. 2.6 a,b,c). One sample is done per each variety.

PACKAGING

STORAGE

STORAGE Figure 2.1 Description of nuts processing operations from harvest to storage. Nuts can be delivered to processing facility immediately after harvest or can be processed directly from the farm

2.1.

Delivery to processing facility and sampling

Figure 2.6a. Example of nuts in bulk sampled by a manual probe (Photo by Agriserbia)

The hazelnuts can be delivered in small bags (Fig. 2.2), in big-bags (Fig. 2.3) or in bulk (Fig. 2.4).

Figure 2.6b. Example of nuts in bulk sampled by a semi-automatic probe.

The operator manually inserts the probe into the truck profile. The probe sucks the nuts and transfers the sample through a pipe to the collection point (Photo by Ferrero HCo)

Figure 2.6c. Example of nuts in bulk sampled by a completely automatic probe. No need of operators (Photo by Ferrero HCo)

The sample size is proportional to the quantity of product delivered (see table 2.1).

The sample obtained is then divided into three sub-samples of equal size: one sample is immediately analysed and the other two are kept in case of complaints about the quality results.

Table 2.1 Example of nuts sampling method of nuts delivered to the processing facility

Figure 2.2. Example of in-shell nuts delivered in properly ventilated small bags (Photo by Agriserbia)

Figure 2.3. Example of in-shell nuts delivered in properly big bags (Photo by Agriserbia)

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Figure 2.4. Example of nuts delivered in bulk (Photo by Agriserbia)

QUANTITY OF DELIVERED LOT FOR ONE VARIETY Tons

SAMPLING QUANTITY Kgs

INITIAL SAMPLING DIVISION kgs

<10

40

10

10-20

70

10

>20

100

10 9

FINAL SAMPLING DIVISION 2 kg +2 kg +2 kg (One sample will be directly analyzed while the other two will be used in case the farmers complains about the first quality results)

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POST-HARVEST GUIDELINES

The sample is weighed and shelled and all visual and hidden defects such as cimiciato and/or rotten are identified and measured through appropriate instruments. In this phase, the rough quantity of external bodies (such as stones, leaves, etc.) and moisture content of the product are also measured in order to assess the need for cleaning and drying process.

parameters, randiman 2.2. Quality and quality grade determination 2.2.1. Quality parameters The parameters evaluated on the sample when determining the quality of the delivered hazelnut are the following: • Moisture: moisture content expressed as a % of the weight of the shelled hazelnut (seed or kernel), using an appropriate moisture meter instrument (i.e. electro moisture meter or similar, see 2.2.2).

Figure 2.7 Rotten hazelnut (seed) before and after cutting the seed (Photo by Ferrero HCo)

• Empty nuts: nuts without kernel inside. This parameter when high can seriously affect the Randiman.

• Old hazelnuts: nuts from the previous year, easily recognizable by the typical black color.

• Rotten hazelnut: this term indicates any hazelnut having visible or hidden rot signs. Within this definition are included hazelnuts that are moldy, rotten and infested by worms, with a defect that can totally or partially affect the kernel. If the spoilage is inside the nuts (shelled) and is only visible after cutting, this will be defined as “hidden rot”. If the defect also affects the external part of the nuts and can therefore be seen from the outside, it is defined as “visible rotting” (Fig. 2.7).

• Corken hazelnut (cimiciato): the term “corken” indicates damage caused by insects from the Rhynchota family. These insects, commonly known as “bugs”, feed by piercing the hazelnut. Depending on the time the nut is pierced, the bugs’ activity will either kill the seed, resulting in an empty shell, or cause partial shrivelling which causes the affected seed to have a bitter flavour (cimiciato). Defects may be visible externally, “visible corken”, or by cutting the seed “hidden corken”: this will normally appear as a round, whitish area of variable dimensions, with a darker edge: white edge of the same defect won’t be considered. Sometimes there may be malformations affecting all or part of the seed (Fig. 2.8).

• Shrivelled hazelnuts: “shrivelled” are seeds that for various reasons have not reached normal development and are smaller in size and whose surface is completely or partially wrinkled and shrivelled (Fig. 2.9).

• Hazelnuts out of shell and scrap: incorrect drying, may cause breakage of the hazelnut shell and a subsequent qualitative degradation.

• Foreign bodies: this term indicates anything that is neither hazelnut nor shell, such as stones, earth, splinters of wood etc. The most commonly found defect is the presence of stones.

Figure 2.8 Corked hazelnut (seeds) before and after cutting the seed. The corken defect, known also as ‘cimiciato’ is caused by feeding of bugs on in-shell hazelnut during fruit development (Photo by Ferrero HCo)

Figure 2.9 Shrivelled hazelnuts are seeds smaller in size and totally or partially wrinkled (Photo by Ferrero HCo)

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POST-HARVEST GUIDELINES

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2.2.2. Laboratory equipment for quality analysis of hazelnut The laboratory equipment (Fig. 2.10) used for the evaluation on the nuts sample includes: • Scale (Fig. 2.11) used for weighing the received nut samples (Max 4 / 10 kg – Min 40 gr – e=d= 2/5 g); • Cracking machine suitable for small samples used for shelling the sample (Fig. 2.12); • Moisture halogen analyzer used to check the moisture content of the kernels (Fig. 2.13); • Professional blender (adapt to dry fruit) used to mince kernels for the moisture check (Fig. 2.14); • Precision scale (Fig. 2.15) used for measuring the visible defects (including foreign bodies, visible rotting and shrivelled kernels, etc.) (200-0.05 g); • Inner defects analyzer (Fig. 2.16) used to detect inner hazelnut defects like hidden rot and hidden cimiciato.

Figure 2.15 Precision scale to measure defective nuts (Photo by Agriserbia)

Figure 2.16 Inner defects analyzer: before and after cutting (Photo by Agriserbia)

2.2.3. Randiman determination The randiman determination is essential to evaluate the quality of the lot and also to define its value (price). The randiman calculation is done on a clean and dry sample. The steps to follow for randiman determination are (Fig. 2.14): • Visual inspection of hazelnut in shells: in order to identify and isolate foreign bodies, hazelnuts detached from shells, wastage and possible varietal mix present in the lot.

• Shelling and inspection of visible defects: after the shells have been separated from the nuts, a further visual inspection will be carried out in order to identify and separate any hazelnut affected by visible rotting or shriveled seed.

• Weighing of hazelnut and calculation of actual randiman: after shelling and sorting of shells, foreign bodies and nuts with visible defects, the remaining hazelnut will be weighed to determine the randiman as follow: Figure 2.10. Equipment used for quality analysis of nuts delivered to a processing facility (Photo by Agriserbia)

Figure 2.11. Scale to weigh nut samples (Photo by Agriserbia)

RANDIMAN (%) =

Weight of shelled nuts * (2,000 gr.) **

x100

* in grams, after shelling and sorting of foreign bodies, nuts detached from shells, wastage, shrivelled and those with visible rotting. ** weight of the clean and dry sample of in-shell nuts

The randiman may vary from 38-40% to 45-47%, depending on the varietal characteristics, seasonal trend, agronomic management and post-harvesting process.

2.2.3.1. Determination of visible defects

Figure 2.12 Cracking machine to shell nut samples (Photo by Agriserbia)

Figure 2.13. Moisture halogen analyzer (Photo by Agriserbia)

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Figure 2.14. Professional blender (Photo by Agriserbia)

The determination of the rates of visible defects which are (i) visible rotting and (ii) shrivelled hazelnuts, is done at the same time as the determination of the randiman. As mentioned in the previous section, the weight of these two defects shall be subtracted from the weight of the shelled sample before proceeding with the determination of the randiman.

The rate of each visible defect on the total weight of the shelled sample is calculated as follows: 13

POST-HARVEST GUIDELINES

(i)

(ii)

POST-HARVEST GUIDELINES

Weight (in gr) of nuts with visible rotting

Visible rotting (%) =

Total weight (in gr) of the shelled sample

x100

Weight (in gr) of shrivelled hazelnuts

Shrivelled hazelnuts (%) =

Total weight (in gr) of the shelled sample

x100

2.2.4. Determination of quality grade The quality grade is assessed through the determination of hazelnuts affected by visible corken defects, visible rotting defects and hidden defects and hidden defects (hidden rotting and hidden corked) (Fig. 2.17).

2.2.4.1. Determination of visible corken kernel (or cimiciato) From the sample resulting from randiman determination process, the hazelnuts with visible corken damages are separated and weighed in order to establish the rate (%) of this defect:

Visible corken (%) =

Weight (in gr) of nuts with visible corken Weight (in gr) of the shelled sample

x100

2.3.

Other quality parameters

The price paid to the producer supplying the hazelnuts is determined on the basis of quality parameters defined by the confectionery industry. The varietal quality is the main parameter since the size and shape of nut, kernel percentage, peelability and organoleptic characteristics are parameters controlled mainly by the genotype. Consequently, the price of the lots is mainly established with reference to the cultivar. The main quality parameters controlled by the genotype are: • Shape and size of the hazelnut: round shape is preferred by the confectionery industry, since less product losses at the time of shelling; whole kernels are used for the most valuable products. The calibers (diameters) of the seeds preferred by the industry are 12-14 mm; larger or smaller sizes can have particular uses (for example in thin chocolate bars for the smaller ones) or can be destined for the production of semi-finished products (especially pasta and grains).

• Kernel percentage (or shelling yield): each variety has a percent kernel that depends on the genotype (from 38 to 50% in some Turkish cultivars), but is also influenced by climate and management conditions, in particular by the availability of water.

• Peelability of the seed: the peelability refers to the ease of removal of the episperm from the seed after roasting (Fig. 2.18) and is considered as optimal when 80% of the seed surface is free of episperm. The peelability depends on genotype but can be influenced by the seasonal climatic trends and the correct orchard management (fertilization and irrigation). Poor peelability is considered a defect in the processing phases, and at the time of sorting the residual episperm could hide the possible presence of hidden defects.

2.2.4.2. Determination of the hidden defects Hidden defects are divided into “hidden rotting” and “hidden corken”. The determination of the rate (%) of these two defects is carried out on the cut seeds of the shelled sample, without the seeds affected by visible defects, previously assessed.

Figure 2.18 Degree of peelability in different hazelnut cultivars (Photo DISAFA - University of Torino-Italy)

Figure. 2.17 Scheme for randiman and quality grade calculation (Photo by AGRISERBIA)

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POST-HARVEST GUIDELINES

CLEANING AND DRYING OF HAZELNUT The product has to be preferably cleaned and dried as soon as possible after harvesting to avoid rising humidity which could compromise the quality of the hazelnuts. The best solution is to clean and dry the nuts within the day of collection (24 hours), and where this is not feasible, within the shortest possible time, especially if harvested after rains or with high moisture contents (>12%).

Figure 3.1. Example of a complete Cleaning&Drying plant’s layout (Photo by Agriserbia)

3.1. Cleaning hazelnut Most of the harvesting machines do not allow to accurately separate fruits from soil particles and stones of the same size as the hazelnuts; also, leaves, empty hazelnuts and small pieces of wood are difficult to separate from the hazelnut during harvest operations.

The cleaning and drying process generally starts from a hopper when the product, arriving from the field, is unloaded (Fig. 3.2). The product then pass through a separator fan with a rotary sieve (or other aspiration systems) to remove the lighter particles and then through a swilling tank with water to remove the stones.

In order to be sure that a clean product gets inside the drying silos, further manual sorting can be done, where operators can remove materials that have “escaped” the cleaning system.

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Figure 3.2. Nuts arrived from the field and discharged into a hopper (Photo by Agriserbia)

POST-HARVEST GUIDELINES

POST-HARVEST GUIDELINES

3.1.1. Dry cleaning system

3.1.2. Water cleaning system

The dry cleaning machine uses air flow generated by a separator fan with a rotary sieve, useful for separating impurities of different dimensions and weight with respect to the caliber of the fruit, taking advantage of their different specific weight (Fig. 3.3.). Cleaning machines can be electrically or mechanically powered (with their own motor or driven by the tractor’s PTO) and can be operated by a single operator. Different models are available on the market that use simple separator fans or more complex aspiration systems. The work capacity of these machines depends on the operating systems (from 600-1200 kg / h up to 4000-4500 kg/h). The more complex cleaners require a first passage inside a sieve in which the coarser impurities (soil and large residues) are eliminated, a second passage through ventilation that eliminates the lighter parts (leaves, empty fruits, twigs) and a final step that eliminates the smaller portions. There are also on the market other systems cleaning the products well by aspiration and the use of this or other technologies needs to be evaluated based on parameters like system capacity (total quantity of crop to be processed per day), quantity of foreign bodies harvested and delivered to the facility and others.

The system is needed solely to sort out the stones from the hazelnuts in a really quick passage. The operation is automatic and easily managed through control panels: only the adjustment of few elements requires a manual regulation. The water cleaning system takes place in a swilling tank (Fig. 3.4) with an auger, equipped with a recirculation pump. The product introduced into the tank quickly floats and is pushed by a stream of water (caused by the immersion pump) towards a grid, where the water rushes into the recovery tank while fruits roll towards the exit, while heavier bodies, such as stones, go to the bottom and are expelled by an auger.

The washing tank is combined with water outflow systems which can consist of an inclined perforated auger, for the simplest systems, or a water outflow sieve consisting of a single rotary mesh screen, for processing systems of larger dimensions. The tank can also be combined with a perforated sorting belt, equipped with a fan that allows the flow of water from the tank and visual inspection of the product before it arrives in the dryer (Fig. 3.5). When water washing is used, fruits that come out of the washing should be promptly dried. The advantage of cleaning with water is the speed of the operation (fi. 9 tons / hour max of working capacity) and the excellent effectiveness compared to traditional mechanical systems.

Figure 3.4 Water cleaning system: nuts dropping into a swilling tank (Photo by Agriserbia)

Figure 3.5 Water cleaning system: hazelnuts pass on a perforated sorting belt, equipped with a fan that allows the flow of water from the tank and visual inspection of the product (Photo by Agriserbia)

Figure 3.3. Examples of cleaning dry systems (Photo by Agriserbia)

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3.2.

The drying process is influenced by different factors:

Drying hazelnut

• Temperature of hot air

The hazelnut has variable moisture upon harvesting which depends on the climatic conditions of the previous days; it generally requires a more or less long drying period to reach the commercial humidity values required for subsequent storage.

• Thermal differential (temperature difference between hazelnuts and hot air) • Initial hazelnut moisture content • Extension of the surface of contact • Degree of air exchange

3.2.1. Natural drying

• Material used in the construction of dryer (influence of heater)

Traditional drying involves leaving the hazelnuts in a single layer exposed to the sun in the courtyard (Fig. 3.6), with frequent mixing of the mass. This technique, still used in different parts of the world and in some small companies, takes at least 2-3 weeks depending on climatic conditions and management of the operation; it is not recommended because drying too slow exposes the hazelnuts to acidification and rancidity phenomena which reduce the quality and shelf life of the product and increase the possibility of aflatoxins’ development.

• Air humidity and Climate conditions in general Suggestions on how to manage correct artificial drying (indications are intended per single cycle): • Start the air ventilation and auger when the dryer is half full: this helps to start removing the excess of external water without waiting for the complete loading of the dryer • Insert in the dryer hazelnuts with same kernel humidity (homogeneity of kernel humidity of the lot is essential)

Some useful suggestions for proper natural drying are:

• Set the drying temperature lower than 40°C

• Don’t keep hazelnuts in a pile or inside a jute bag or in mass after harvest

• Do not apply more than 6-8 hours of drying (burner + fan) • To estimate the correct drying duration, take into account the starting kernel humidity.

• Place the hazelnuts immediately in a single layer • Dry hazelnuts in clean area avoiding the direct contact with the soil/ground • Allow air flow through hazelnut layer

• The drying duration is empirically calculated considering that it takes about 1 hour of drying to lower the humidity by 1%

• Monitor the moisture of kernel each day to reach the final goal (6% of kernel humidity).

• After drying, set a ventilation cycle (using only fan and auger)

Figure 3.6 Natural drying: hazelnuts exposed to the sun in a courtyard (Photo by DISAFA – University of Torino - Italy)

3.2.2. Artificial drying The use of specific dryers is the safest method to ensure the quality and safety of our crop. A correct drying increases the shelf-life of the product by improving chemical and microbiological stability and avoiding formation of aflatoxins for at least one year.

The drying silos continuously mixes the product using special augers (Fig. 3.7) and the nuts are dried by hot air produced by burners and fed through a ventilation system. During this phase, which depends on the initial moisture content of the hazelnuts, the operator can sample the product inside and deliver it to the laboratory to check the moisture content reached by the product itself. Once 6% of seed moisture has been reached, the product has completed its cycle and the entire lot can be sampled again for the randiman calculation (see 2.2.3) and subsequent packaging in big bags.

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• The hot dried hazelnuts are unloaded once they reach about 7% of humidity; in the following days, they will automatically and naturally reach about 6% of internal moisture content.

Models of dryers with different characteristics of capacity and type of power are available on the market. The capacities of the dryers range from small models (2-6 cubic meters) up to dryers of 30 cubic meters (for hazelnuts 1 mc = 0.50 t; from 1 to 15 t). The small-sized dryers (2-6 mc), suitable for small companies, are available in wheeled or carried by tractor models, diesel/gas fuel or electrically powered (including model that requires 220 Volts power supply and consumption lower than 3 KW, in order to be used with normal domestic meters). The larger models are fixed and have capacities up to 30 cubic meters; they can be arranged in series (Fig. 3.8) until reaching the capacity required by the processing line (shelling systems).

Figure 3.7 Special auger inside the dryer used to continuously mix the product during drying (Photo by Agriserbia)

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POST-HARVEST GUIDELINES

PACKAGING AND STORAGE

After drying, hazelnuts are kept in bulk, big bags or silos, waiting for following processing. The prolonged farm storage is strongly discouraged, since the buildings available in the farm are affected by external temperature and moisture conditions, which are not always optimal for maintaining the quality of the hazelnuts. On the contrary, when hazelnuts are delivered immediately after harvesting to processing centers, they are promptly dried and stored in proper conditions allowing the crop to preserve its characteristics for a longer time.

Figure 3.8 Dryers in series (capacity of 12-14 tons each) (Photo by Agrichile)

A possible complete cleaning and drying equipment layout includes (Fig. 3.9): • Hopper for product unload • Bucket elevators • Separator fan (dry cleaning) • Swilling tank (water cleaning) • Water drainage sieve • Perforated belt with ventilator • Load and unload augers • Dryers (artificial drying) • Conveyor belt.

Figure 3.9 Example of small and complete cleaning and drying system for hazelnut (Photo by Agriserbia)

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4.1.

POST-HARVEST GUIDELINES

Types of packaging

- Small bags: they need to allow crop ventilation and facilitate handling, transport and storage - Big-bags are bags with very large volumes (500-1.000 kg) generally composed of simple plastic material or by overlapping several layers of different material (e.g. polyethylene, nylon and aluminum). They represent the best way to store hazelnut since it ensures excellent insulation from the external environment. Big bags can be directly and automatically filled with a specific system (Fig.4.1) immediately after the cleaning and drying process.

Figure 4.1 Automatic big bags’ packaging and weighing system after cleaning&drying (Photo by Agriserbia) Figure 4.3 Silos built in series to store big quantities of cleaned and dried product in-shell (Photo by Agrichile)

Figure 4.2 Example of Big-bags’ storage (Photo by Agriserbia)

4.2. In-shell hazelnuts storage Hazelnuts are characterized by a low residual moisture content and very weak respiratory activity at room temperature.

Despite this, the presence of oxygen is the factor that most reduces the quality of hazelnuts during storage: hazelnuts kept in contact with the air undergo chemical and organoleptic deterioration, regardless of the temperature. However, enzymatic and chemical rancidification processes, and vitamin E degradation, are considerably retarded at low temperature.

Mold and insect activity is virtually eliminated near freezing temperatures. In-shell hazelnuts have to be stored in clean and ventilated warehouse (no T controlled) with relative humidity around 65%-70% for max. 90 days (Fig. 4.2).

- Metal mesh containers are generally used for temporary storage of nuts before subsequent processing keeping the product clean and off the ground (Fig. 4.4); these containers allow good air circulation, can be easily stored stacked and are easy to move. They are successfully used in small companies that manage a limited amount of product.

Preferably, storage has to be performed in containers or big bags allowing the air ventilation, useful for keeping the levels of temperature and humidity homogeneous. Hazelnuts are subject to absorbing smells of the environment in which they are stored, therefore storage in a clean environment free of extraneous odors and in the absence of other fruit and vegetables. Hazelnuts are also very sensitive to damage from ammonia so that even low concentrations (5-10 ppm) can cause blackening.

4.2.1. Nuts storage in farm Big bags or other bags: • Keep in a dry area with good air circulation avoiding plastic bags • Keep the bags raised from the soil • All the bags have to be labelled with proper information.

Hopper silos: are very big containers to store big quantities of products designed to store seeds keeping the product off the ground to prevent moisture and reduce the possibility of breakage. They are realized in steel and built in series (Fig. 4.3), then available only for big companies or big nut processing facilities.

Figure 4.4 Metal mesh containers for temporary storage of calibrated dried nuts before further processing (Photos by DISAFA – University of Torino - Italy)

After the storage, the lots properly labelled and packed are delivered to the Ferrero plants for further processing (Fig. 4.5) 24

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POST-HARVEST GUIDELINES

CALIBRATION AND SHELLING NUTS

Figure 4.5. Loading of cleaned and dried lots to Ferrero’s facilities

4.2.2. Nuts storage in processing facility The optimal storage conditions are a combination of low temperature and percentage of relative humidity less than 70%.

The suggested time of storage of in-shell hazelnuts in normal atmosphere condition is (Table 4.1): - 3-4 months at 3-5 °C and at RH of 50-70% - 5-6 months at 1-2 °C and at RH of 50-70%.

Better storage conditions may be provided by a combination of low temperature and modified atmosphere (saturated with N2 and/or CO2). It was demonstrated that the use of high concentration of nitrogen (98–100%) in combination with low temperature (4 °C) are the best solution for maintaining unchanged color, firmness, acidity and peroxide values of the kernels. In modified atmosphere cells (Oxygen <1%; Carbon dioxide 0-0.3%; N2 about 99%) with 55-60 % RH and a temperature of 2-4 °C, shelled hazelnuts can be stored for 13-14 months.

Table 4.1 Duration of nuts storage in different temperature i.e. atmosphere conditions.

Products

Temperature

Relative Humidity %

In-shell nuts

3-5 °C

50-70 %

In-shell nuts

1-2 °C

50-70 %

Shelled nuts

2-4 °C

55-60 %

Oxygen % Normal atmosphere Normal atmosphere <1%

Carbon Dioxide %

Nitrogen %

Storage duration

-

-

1-5 months

-

-

4-6 months

0-0.3 %

99

13-14 months*

*Fondazione Edmund Mach-IASMA: weight loss of 0,1 % after 14 months of storage Another effective method to preserve quality characteristics is the storage in refrigerated, vacuum-packed environments.

Placed inside envelopes or big-bags after flushing with nitrogen and subsequent heat sealing of the packages, hazelnuts can be kept under vacuum for 9 months at 3-4 °C, and for 7 months if stored at room temperature.

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The shelling of the hazelnuts aims to eliminate the shell while keeping the kernel intact; for this reason, the hazelnuts are previously divided into homogeneous sizes. The sorting is carried out using a nut calibration machine (calibration sieves) that uses standard diameter of rotating perforated cylinders with holes of increasing diameter (eg 17-18-19-20 mm, Fig. 5.1). Once batches of homogeneous caliber have been obtained (Fig. 5.1), they are sent to shelling machines equipped with rotating and fixed grooved rollers, at an adjustable distance according to the size of the hazelnuts.

After shelling, kernels are cleaned by means of ventilation systems, screens and acoustic resonance machines that separate whole seeds from the broken ones, from pieces of shell and from any other solid impurities. The acoustic resonance sorting machines are equipped with a foreign body detection device, which works by recognizing the resonance frequency produced by whole seeds, which is different from that of shells, unshelled or partially shelled hazelnuts, stones and fragments of glass and metal.

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Figure 5.1 Calibration machine using holes of different diameters in order to obtain lots of product with the same size (Photo by Agrichile)

Manual sorting is done during the processing phase (Fig. 5.2).

Figure 5.2 Manual sorting on hazelnut kernels (Photo by Agrichile)

Figure 5.3 Laser machine for kernel sorting (Photo by Agrichile)

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REFERENCE LIST

REMARKS

Botta, R., Valentini N., Di Renzo L., 2018. Chapter: Qualità e post-raccolta. In: Il nocciolo. Progettazione e coltivazione del corileto. Edagricole, pg:155-176.

Contini M., Cecchini M., Massantini R., Monarca D., Roberto Moscetti R., 2010. Proprietà nutrizionali-salutistiche e conservazione della frutta secca in guscio. Review n. 12 - Italus Hortus 17 (4): 13-27.

Fardelli A., 2008. Effetto dei sistemi di conservazione sulla qualita’ delle nocciole (Corylus avellana L.). Tesi di Dottorato XX CICLO, Università degli Studi della Tuscia. Viterbo, Italia. Pp: 133.

Ghirardello D., Contessa C., Valentini N., Zeppa G., Rolle L. Gerbi V., Botta R. 2013. Effect of storage conditions on chemical and physical characteristics of hazelnut (Corylus avellana). Postharvest Biology and Technology, 81: 37-43.

Mencarelli F., Forniti R., Fardelli A., Desantis D., Valentini M., Sequi P., 2007. Atmosfere inerti e temperatura nella conservazione delle nocciole essiccate. Ricerche e innovazioni nell’industria alimentare. Volume VIII. Atti dell’8° Congresso Italiano di Scienza e Tecnologia degli Alimenti (CISETA), RHO (MI), 7-8 Maggio.

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