Chapter 8: Optimum Storing and Shipping Conditions for the Export of Perishable Products

Contents

1. Temperature Requirements
   1.1 Optimum storage and shipping temperatures and requirements per product
   1.2 Optimum shipping temperatures for sea export
   1.3 Cargo mixes and compromise temperatures for nearby Indian and Atlantic ocean destinations
   1.4 Compromise temperatures for air freight
2. Taints, Cross Tainting, and Foreign Odour
   2.1 Products that very easily absorb taints
   2.2 Products that easily give off taints or odour
   2.3 Mixing of produce in storage and transport spaces
3. Time Temperature Tolerances
   3.1 Definition
   3.2 Effect of temperature fluctuations
   3.3 Specific product requirements

    3.3.1 Deciduous and citrus fruit  
   

   3.4 General breakdown per action

    3.4.1 Container handling  
    3.4.2 Conventional deck loading  
   

4. Temperature Management

Introduction

Optimum product storage conditions and temperatures may vary between growing and climatic conditions as well as specific procedures and market requirements. For example, plum cultivars produced in California can be stored at -0.5°C, but the same cultivars grown in South Africa must be stored at a dual temperature of -0.5°C for up to 10 days, after which the temperature must be raised to +7.5°C. Optimum product and air temperatures for products produced in South Africa are summarised in Tables 1 to 7.

Three different temperatures are to be considered during the voyage:

• DAT (Delivery Air Temperature): Temperature of the air just before it comes into contact with the product.
• RAT (Return Air Temperature): Temperature of the air coming directly off the product.
• Optimum Product or Pulp Temperature: Actual temperature of the product flesh.

The optimum product temperature is the only temperature that can be specified and must be strictly maintained. This is achieved by constantly observing the RAT and carefully controlling the DAT at or not more than 0.5°C colder than the specified optimum product temperature. If the RAT is 1°C or warmer than the specified optimum product temperature, cold blasts (lowering of the DAT) must be applied for 3 hours out of every 6 hours. If the RAT does not drop to within 1°C above the optimum product temperature within 24 hours (4 cycles), the PPECB must be informed immediately.

Note: For avocados and mangoes, the optimum product temperature is also the DAT.

1. Temperature Requirements

Specific detailed handling, storage, and transport procedures are revised annually by the PPECB. The following is a brief summary of product requirements.

1.1 Optimum Storage and Shipping Temperatures and Requirements per Product

• Apples:
  Optimum storage temperature: -0.5°C
  Optimum storage RH: 95%
  All South African apples are stored, transported, and shipped at a pulp temperature of -0.5°C. Storage life exceeds 4 months and can be extended to more than 8 months with controlled atmosphere storage. Some cultivars are sensitive to higher temperatures or freezing injury below -1.5°C.
• Apricots:
  Optimum storage temperature: -0.5°C
  Optimum storage RH: 95%
  Very sensitive to warm pulp temperatures. Storage life for sea export is 28+ days at -0.5°C. Proper precooling and air circulation are important.
• Grapes:
  Optimum storage temperature: -0.5°C
  Optimum storage RH: 95%
  Non-climacteric, do not ripen after picking. Must be stored and shipped at -0.5°C and 95% RH to avoid decay and desiccation. Packed in polyethylene bags with sulphur dioxide-generating paper. Should not be shipped with sensitive products like apples.
• Peaches and Nectarines:
  Optimum storage temperature: -0.5°C
  Optimum storage RH: 95%
  May develop woolliness (lack of juice at ripe stage). Prompt and fast cooling to -0.5°C after a short delay is important. Each consignment must be considered individually.
• Pears:
  Optimum storage temperature: -0.5°C (Summer pears: -1.5°C)
  Optimum storage RH: 95%
  Storage life varies by cultivar. Fast precooling and maintenance of the cold chain are crucial. Summer pears are sensitive to temperature fluctuations.
• Plums:
  Optimum storage temperature: varies by cultivar and voyage
  Optimum storage RH: 95%
  Some cultivars develop breakdown if stored at -0.5°C for more than 10 days. Dual temperature storage is used: -0.5°C for 10 days, then 7.5°C for 7 days, then back to -0.5°C.

1.2 Optimum Shipping Temperatures for Sea Export

Optimum carrying temperatures, minimum air delivery temperatures, and fresh air circulation rates for regular atmosphere storage and sea transport are summarised in the following tables. These conditions were developed for long-distance sea voyages.

1.3 Cargo Mixes and Compromise Temperatures for Indian and Atlantic Ocean Destinations

Exporters often need to mix different products into one container or ship’s deck for smaller markets or specialized buyers. Voyage times vary between 5 and 14 days. A unique product temperature compromise system was developed for these markets.

Important notes:

• Listed mixes may not be the best compromise for all products under all conditions.
• Products must always be handled and stored under optimum conditions.
• Special care is needed when containers or produce are transshipped in a different port.
• Exporters must ensure importers are informed about post-discharge handling and storage.

1.4 Compromise Temperatures for Air Freight

Optimum product temperatures for air freight are not always possible. Produce moves quickly through airports and is often mixed. Best compromise temperature ranges per product group are summarised in Table 7.

2. Taints, Cross Taints, and Foreign Odours

These terms refer to a product acquiring a non-typical taste or odour, often from another product or from chemicals/paints used in storage or transport environments.

2.1 Products That Very Easily Absorb Taints

• Dairy products (taint molecules attach to fatty acids)
• Meat (especially high fat content)
• Fruit (e.g., Golden Delicious apples)
• Vegetables (especially those eaten fresh)
• Nuts

2.2 Products That Easily Give Off Taints or Odour

• Chemicals (paints, silicone, rubber, petroleum, exhaust gases)
• Marine products (fresh and frozen fish)
• Onions and garlic
• Potatoes (especially over-stored)
• Capsicum/peppers
• Citrus fruit (oils in skin can taint dairy and meat)

2.3 Methods of Testing for Taints

Sophisticated tests exist but are slow and costly. Sometimes taints disappear when the product is cooked. Evaluate conditions to determine possible taint risk.

2.4 Mixing of Produce in Storage and Transport Spaces

Many taint and cross taint tables exist, but temperature incompatibility often rules out certain product mixes. See Tables 9 and 10 for products that may or may not be stored and transported together.

3. Time Temperature Tolerances (TTT)

3.1 Definition

TTT refers to the total time a refrigerated perishable product can be without cooling during handling and loading. It is the cumulative time in breaks in the cold chain, based on product requirements.

3.2 Effect of Temperature Fluctuations

Temperature increases in chilled and frozen products can negatively affect quality, safety, and appearance. Fresh produce is still alive; higher temperatures accelerate ripening and moisture loss. Microbiological spoilage increases with temperature. Fluctuations cause condensation, leading to rot or ice formation.

3.3 Specific Product Requirements

3.3.1 Deciduous and Citrus Fruit

The TTT for this group is a maximum of 6 hours, considering product respiration and packaging.

3.4 General TTT Breakdown per Action

3.4.1 Container Handling (Deciduous and Citrus Fruit)

3.4.2 Conventional Deck Loading

It is impractical to measure/apply TTTs during conventional deck loading. The rule on maximum pulp temperature increases applies. Decks must be closed and recooling started as soon as the following pulp temperatures are reached:

• All fruit not packed in polyethylene bags except subtropical fruit: 12°C
• All subtropical: 5°C above the temperature
• All fruit packed in polyethylene bags: 8°C
• Pulp temperature in center of pallets: No increase

Tables

Table 1: Optimum Carrying and Minimum Delivery Air Temperatures (°C) and Fresh Air Ventilation (m³/h) for South African Fresh Fruit Export (Non-Cold Treatment)

Notes:

• Fresh air ventilation rates are given as m³/h.
• Conventional shipping spaces should be ventilated to keep CO₂ below 0.5%.
• Plum shipping temperatures depend on cultivar and maturity.

Table 8: Perishables Which May or May Not Be Stowed Under Chilled Conditions in the Same Space

(See original for full matrix. Y = No danger of cross taint, N = Cross taint probable, SR = Slight danger, BR = Danger.)

Table 9: Commodities Which May or May Not Be Stowed in the Same or Adjoining Spaces

(See original for full matrix. Y = No danger of cross taint, N = Cross taint probable, SR = Slight danger, BR = Danger.)

Table 10: Frozen Commodities Which May or May Not Be Stowed in the Same Spaces

(See original for full matrix. Y = No danger of cross taint, N = Decided danger, SR = Slight danger.)