Irradiation to decontaminate herbs and spices 61
3.2 Quality considerations
Spices and herbs are normally used for their volatile aromatic oils and biologically
active principles. They do not contribute much to the nutritional value of food. The
volatile oil in spices could vary from negligible to 13%. Most of the spices and herbs
have a high level of moisture, varying from 16–88% at the time of harvest. After
harvest spices and herbs are dried locally by the farmers and collectors. Spices are
generally produced by small farmers, where traditional systems of cultivation and
drying are used. The moisture content of spices and herbs may vary from 6–12%
depending on the extent of drying and climatic conditions. Often the produce is not
adequately dried, cleaned, graded or packed. It is often the middlemen who collect,
pool, clean, grade and bag the spices, before selling them to traders and exporters.
Ideally, for storage stability, moisture in spices should be below 12%. But often
farmers do not dry the produce to the required extent often unintentionally, but some
times intentionally, to get the advantage of weight.
Open air drying leads to contamination of spices and herbs with soil and dust. The
biotic factors responsible for the deterioration of spices and herbs and the consequences
to consumers are shown in Table 3.1. Contamination of spices and herbs with biotic
agents not only risks the spoilage of the valuable commodity but also poses risks to
human health due to the presence and outgrowth of pathogens and toxin-producing
molds.
Due to low moisture in dry spices and herbs the water activity is often less than
0.60. Thus these commodities are inherently stable during storage. Spices contain a
number of microorganisms as shown in Table 3.2, however, the actual number of
bacteria present may vary from spice to spice (Table 3.3). Spices contain a high load
of spores of bacteria and fungi (Table 3.3). These spores are mainly mesophilic
aerobes, mesophilic anaerobes, and flat sour thermophilic aerobes (Pruthi, 1980).
Spices may also contain human pathogens. This is indicated by the presence of
coliforms and E. coli (Table 3.4), the organisms known as indicators of fecal
contamination and thus the hygiene of the commodity (Farkas, 1988). The presence
of human pathogens such as Salmonella, E. coli, and Bacillus cereus has been well
documented in spices (Pruthi, 1980). Due to low water activity spices and herbs are
inherently resistant to bacterial spoilage.
Fungal contamination and spoilage of spices and herbs could occur either during
drying when the process is slow or if the drying is inadequate, or during post-harvest
storage, especially when relative humidity during storage is high and the temperature
Ta ble 3.1 Biotic factors in quality deterioration of spices and herbs∑ Storage insects- Infestation and deterioration
- Loss of marketability
- Risk unethical use of harmful insecticides
∑ Contaminating microbes- Potential spoilage of spices
- Potential spoilage of food
- Potential human pathogen
- Potential toxin producer
- Loss of marketability
- Risk unethical use of chemicals