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

Optimum Storing and Shipping Conditions for the Export of Perishable Produce from South Africa

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 and Section 10 of this book. 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.

Key Principle:
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. Optimum product temperature is achieved when the RAT is at, but not more than 1°C above, 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), PPECB must be informed immediately.

Note:
For avocados and mangoes, the optimum product temperature is also the temperature at which the DAT should be maintained. Detailed specifications will be given in the Board temperature letter to the Master.

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 cold stored, transported, and shipped at a pulp temperature of -0.5°C. Storage life exceeds 4 months, extendable to 8+ months with controlled atmosphere storage. Some cultivars are sensitive to higher temperatures and 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: 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 SO₂-generating paper. Should not be shipped with sensitive products like apples.
• Peaches and Nectarines:
  • Optimum storage temperature: -0.5°C
  • Optimum storage RH: 95%
  • Susceptible to woolliness (lack of juice at ripe stage). Delaying precooling allows slight ripening before storage. Prompt cooling to -0.5°C after delay is important. Each consignment may require special instructions.
• Pears:
  • Optimum storage temperature: -0.5°C
  • Optimum storage RH: 95%
  • Storage life varies by cultivar (10 weeks to 10 months). Fast precooling and cold chain maintenance are critical. Summer pears are stored/shipped at -1.5°C to avoid ripening. CA storage may double storage life. Summer pears are sensitive to temperature fluctuations.
• Plums:
  • Optimum storage temperature: varies by cultivar and voyage
  • Optimum storage RH: 95%
  • Can be cold stored for at least 28 days if correct temperature is applied. Some cultivars develop breakdown if stored at -0.5°C for more than 10 days; dual temperature storage (initial -0.5°C, then 7.5°C, then back to -0.5°C) is used.

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 are developed for long-distance sea voyages.

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

Exporters to East and West African and Indian Island destinations often need to mix different products in one container or ship’s deck due to small markets or orders. Voyage times are usually 5–14 days. Serious quality problems can occur with transshipped products. A unique product temperature compromise system was developed for these markets (see Table 4.7).

Important considerations:

• 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. Often, refrigeration is not continued after discharge, leading to temperature increases and condensation.

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 to optimize space. Best compromise temperature ranges per product group are summarised in Table 7 and must be strictly applied to minimize quality losses.

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. Strong odours in the environment (e.g., ports) can also cause tainting. Fresh and food produce must never be handled in or exposed to polluted 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, like carrots and tomatoes)
• Nuts (taint molecules attach to fatty acids)

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 when 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 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. Products that may or may not be stored and transported together are summarised in Tables 9 and 10.

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 deep-frozen products can negatively affect quality, food 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 and decay, or ice formation in frozen produce. Constant temperatures are essential once the cold chain starts.

TTTs may vary by product, ambient condition, handling method, and equipment. TTTs for various products are defined in PPECB Handling Procedure documents. Important criteria include:

• Inherent product requirement (e.g., degreened citrus, summer pears)
• Effect of increased temperature on ripening (avocado, mango)
• Effect on condensation (polybag grapes) and frost formation (frozen produce)
• Efficiency of refrigeration unit to recool product
• Cooling rate of carton and pallet (ventilation and position)

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 allowed

4. Temperature Management

(Section content not included in selection, but should cover best practices for maintaining temperature throughout the cold chain.)

Tables

Table 1: Optimum Carrying and Minimum Delivery Air Temperatures and Fresh Air Ventilation for South African Fresh Fruit (Non-Cold Treatment)

Notes:

• Fresh air ventilation rates for containers are given as m³/h. Conventional shipping spaces must be ventilated to keep CO₂ below 0.5%. Fresh air ventilation applies in regular atmosphere mode only. For controlled/modified atmosphere, follow equipment supplier specifications.
• Plum shipping temperatures are determined by cultivar and maturity, selected by the exporter from the updated list of reefer codes.

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

(Table omitted for brevity; see source 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 in all probability take place

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