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, 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.

Three different temperatures are to be considered during the voyage:

• DAT (Delivery Air Temperature): The temperature of the air just before it comes into contact with the product.
• RAT (Return Air Temperature): The temperature of the air coming directly off the product.
• Optimum Product or Pulp Temperature: The 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, 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 cultivars are stored, transported, and shipped at a pulp temperature of -0.5°C. Some cultivars are more sensitive to higher storage and transit temperatures. Red types with lower sugar content are more susceptible to 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 exceeds 28 days at -0.5°C.
• Grapes:
  • Optimum storage temperature: -0.5°C
  • Optimum storage RH: 95%
  • Non-climacteric fruit; must be stored and shipped at -0.5°C and 95% RH to avoid decay and desiccation.
• Peaches and Nectarines:
  • Optimum storage temperature: -0.5°C
  • Optimum storage RH: 95%
  • May develop woolliness if not handled correctly. Prompt and fast cooling to -0.5°C after a short delay is important.
• Pears:
  • Optimum storage temperature: -0.5°C (summer pears: -1.5°C)
  • Optimum storage RH: 95%
  • 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 require dual temperature storage: -0.5°C for 10 days, then 7.5°C, 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 of perishable products from South Africa are summarised in the following tables. These conditions were developed and tested for long 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. Recommendations:

• The 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 well informed on post-discharge handling and storage.

1.4 Compromise Temperatures for Air Freight

Optimum product temperatures for air freight are not always possible. Produce may be mixed to ensure optimum utilization of storage and air freight space. The 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 used in storage or transport.

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 compatibility.

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, or the cumulative time in breaks in the cold chain. TTTs are based on product requirements, not logistical processes.

3.2 Effect of Temperature Fluctuations

Temperature increases in chilled and deep frozen products can negatively affect quality, food safety, and appearance. Fluctuations can cause condensation, leading to microbiological growth or ice formation. Constant temperatures are essential once the cold chain is initiated.

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 and apply TTTs during conventional deck loading. The rule on maximum pulp temperature increases applies. Decks must be closed and recooling commenced as soon as the following pulp temperatures are reached:

• 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

4. Temperature Management

Section not detailed in the provided text.

Tables

Table 1: Optimum Carrying and Minimum Delivery Air Temperatures and Fresh Air Ventilation

Notes:

• Fresh air ventilation rates for containers are given as cubic meters per hour (m³/h).
• Conventional shipping spaces must keep CO₂ below 0.5%.
• Plum shipping temperatures are determined by cultivar and maturity.

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

(Table omitted for brevity; see original for full matrix.)

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

• Y = No danger of cross taint
• SR = Slight danger of cross taint
• BR = Danger of cross taint
• N = Cross taint will probably take place

(Table omitted for brevity; see original for full matrix.)

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

• Y = No danger of cross taint
• SR = Slight danger of cross taint
• N = Decided danger of cross taint

(Table omitted for brevity; see original for full matrix.)