Packaging and storage of herbs and spices 99
Escherichia coli is found less frequently and usually in low numbers (<10 CFU
per gram). Salmonella is found occasionally in a wide variety of spices and has been
responsible for a number of outbreaks of salmonellosis. Enterococci are present in
approximately 50% of spices, usually in low numbers and rarely exceeding 10,000
colony-forming units per gram. Moulds are frequently present on spices, usually at
levels of less than 100,000 colony-forming units per gram, but yeasts are rarely
found. The types of mould found include Aspergillus spp, Penicullum spp, Rhizopus
spp. and Spicara spp. Some moulds capable of producing mycotoxins have been
found in a range of spices including black pepper, ginger, turmeric, nutmeg, red
pepper, cumin and mustard seeds. Nutmeg and red pepper is usually prone to aflatoxin
production but levels are usually low, usually less than 25 mg/kg.
5.9.1 Strategies for reducing microbial load in herbs and spices
The food industry has long been aware of the risks associated with unprocessed herbs
and spices and a variety of measures to eliminate or counteract microbial contamination
have been used and are used today. However, many of these measures have, with
time, been declared as dangerous (e.g., ethylene dioxide treatment) or unacceptable
to most consumers (e.g., irradiation). Chemical preservatives in food items, such as
sulphur dioxide, work by inhibiting the microbial uptake of oxygen thereby restricting
their growth. Consumer reaction to E numbers has led manufacturers to remove
preservatives where practical, thus placing further pressure on the herb and spice
industry to supply ever-tightening microbiological specifications. Indeed, there is
evidence that certain food preservatives such as nitrates and nitrites react in the
presence of spices producing potentially carcinogenic nitrosamines.
Current strategies to process herbs and spices to reduce their microbial loads to
acceptable levels include:
∑ Improved agriculture. The world’s largest spice houses are working increasingly
closely with growers and farmers and, by modifying irrigation and fertilizers, it
is possible to produce a cleaner raw material for processing. This is effective in
reducing microbial loads but cannot eliminate risks as the product is still largely
processed in the open air.∑ Product selection. Assessment of numerous batches of herb and spice products
and the selection of the microbiologically cleanest can be effective.
∑ Irradiation. Ionizing radiation, which disrupts bacterial chromosomes to effect
reduction of microbiological load, is highly effective but has a very poor public
image.∑ Heat treatment. Whole or ground herbs and spices are pasteurized by flash
processing with steam or heated dry air.
∑ Flavour extraction or oleoresins. Steam distillation will extract the volatile flavour
principles (essential oils), which due to the process are microbiologically sterile.
Solvent extraction will additionally remove the non-volatile compounds. These
extracts are known as oleoresins and contain the whole flavour character of the
raw material.∑ Encapsulation of herb and spice extracts. An encapsulation process converts
liquid essential oils or oleoresin extracts into free flowing powders.