RAW MACADAMIA PRODUCT QUALITY SPECIFICATIONS

INTRODUCTION

Minimum quality standards for South African macadamias were first agreed to and implemented by marketers in 1994. These covered the main quality parameters affecting kernel rancidity (free fatty acids and peroxide value), hygiene (Coliforms and E.Coli) and moisture level (moisture content %). These minimum quality standards have now been extended to include additional quality parameters, providing a more comprehensive definition of quality specifications in line with international trends.

PREMIUM GRADE MACADAMIA QUALITY SPECIFICATIONS

The agreed quality specifications for “premium” grade raw macadamia kernel are summarised in Table 1. Those quality parameters requiring a certificate of analysis from the supplier as a standard practice are denoted with an asterisk. For the remaining quality parameters a certificate of analysis could be made available to the buyers by the suppliers on request.

GUIDELINE STANDARD STYLE SPECIFICATIONS

There is no single standard set of Style Specifications for South African macadamias, nor is there one single international standard for Style Specifications. The following is given as a guideline only as it most closely matches most of the macadamia styles as traded on international markets, and could therefore perhaps become the basic international standard:-

STYLE                         SPECIFICATIONS

0                                  Min 95% whole kernel >21 mm

1                                  Min 95% whole kernel >16 mm

2                                  Min 50% whole kernel >12 mm

3                                  Min 15% whole kernel plus halves >12 mm

4                                  Min 80% half kernel >9 mm, remainder pieces >9 mm

5                                  Large chips 9 mm – 12 mm

6                                  Small chips 6 mm – 9 mm

STORAGE OF VACUUM PACKED RAW MACADAMIA KERNEL

Vacuum packed raw macadamia kernel should be stored in a cool (15°C to 25°C), dry and well ventilated area. Stored under these conditions, raw macadamia kernel which conformed to all the quality specifications at packing, will maintain this quality for 16 to 18 months without any serious quality deterioration. This length of time of quality preservation is of course only achieved if the correct vacuum pouch material, with the oxygen and water vapour transmission rate properties as described below is used:-

On removal from the vacuum pouch, raw macadamia kernel will maintain freshness, if placed in an airtight container in a refrigerator, for at least 2 months. If, after removal from the vacuum pouch, raw macadamia kernel is left unsealed, or even kept in a thin polyethylene or other plastic bag, at ambient conditions, quality deterioration will be very fast and off odours and flavours will begin to be detected after only 3 to 4 weeks, after which rancidity sets in, making for a very bad macadamia eating experience.

Work done by Cavaletto et al (1966) showed that raw macadamia kernel stored at 1.4% moisture in vacuum packed pouches, showed excellent stability at all storage temperatures for 16 months. The storage temperatures compared in this study were 35°F (5.5°C), ambient and 100°F (37.5°C) in both light and dark conditions. “Stability” measures were:

Raw kernel flavour

Raw kernel total sugar content

Raw kernel reducing sugar content

Raw kernel free fatty acids

It was only at higher moisture contents of kernel vacuum packed and stored in this experiment, that quality deterioration as measured by the abovementioned parameters, was detected over time. Since all South African product is vacuum packed at kernel moisture contents <1.5%, it would appear from this work that even temperatures up to 37.5°C do not bring about quality deterioration over 16 months.

Yet another study, conducted by Bowden and Reeves (undated) in Australia, showed that as long as raw kernel was sealed (either vacuum packed or non-vacuum packed) in pouches of the correct material meeting the oxygen and water vapour transmission rates as defined in an earlier paragraph, it could be stored for up to 8 months under Brisbane ambient conditions with virtually no deterioration in quality. In this instance, the quality parameters measured were:-

Raw kernel flavour and odour    (6 member panel)

Roasted kernel colour, flavour and texture  (20 member panel)

Raw kernel peroxide value and free fatty acids

Raw kernel total sugar and reducing sugar contents

Despite all of this experimental evidence, quality preservation can be ensured with confidence if the recommended 15°C to 25°C storage temperatures can be maintained in a well ventilated dry storage area.

Reference:

Cavaletto, C., Dela Cruz, A., Ross E. and Yamanoto, HY. 1966 Factors Affecting Macadamia Nut Stability. Food Technology – August 1966

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