Dates - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 180

Table 10.2. Quality definitions of attributes based on consumer preferences.

Attribute Maximum Score Quality Definition

Color 16.5 Good-quality dates tend to be light brown in color

Appearance 13.8 Most preferable dates tend to be regular and long

Sweetness 13.7 Preferred dates tend to be moderately sweet

Fruit size 9.5 A good-quality date fruit tends to be moderately large

Chewiness 7.8 A date of good quality ranges from slightly to moderately chewy

Flesh thickness 7.0 The flesh thickness of a good-quality date fruit ranges from moderately

thick to thick

Solubility 7.0 A good-quality date tends to be moderately soluble to very soluble when

consumed

Elasticity 6.6 Dates of good preference tend to range between slightly elastic and

moderately elastic

Texture and mouth feel 6.3 A good-quality date tends to have a smooth texture and mouth feel

Mouth shear 6.2 A slight force is needed to shear or tear a good-quality date fruit

Pit size 5.6 The pit of a good-quality date tends to be medium in size, i.e., neither big

nor small

Source: Ismail et al. (2001).

palm, the maximum dimethoate residue was recorded after
45 days of injection (1.98 mg/kg) followed by a sharp de-
cline in sample collected afterward and disappeared in the
75-day sample and later.

are present only at the Rutab stage in some varieties (Tafti
and Fooladi, 2005).

Spoilage in Ta m a r stage
Dates, like any other agricultural produce, are subject to
microbial contamination in the field and during handling
processes. There is a very limited amount of work done on
the microbiology of date, especially in the main countries
of production. Nussinovitch et al. (1989) reported colony
counts of soft dates in the Ta m a r stage of the order 10 4 cfu/
g lactic acid bacteria and 10 2 cfu/g yeasts. El-Sherbeeny
et al. (1985) detected S. aureus and aerobic colony counts of
6.3

Pollutant residues in dates
Ebadi et al. (2007) determined the levels of polycyclic aro-
matic hydrocarbons (PAHs) in samples of date palm. The
mean levels of total PAHs ranged from 4.44 to 15.96 μ g/kg.
In fruits, the presence of PAHs originates mainly from
deposition of air pollution particulates on their surfaces
(Larsson, 1986).

10 5 cfu/g in loose dates. Postharvest fungi were iso-
lated from deteriorated date palm fruits. Some of these
fungi are Aspergillus niger, A. ochraceus, Penicillium
corylophilum, P. citrinum, P. funiculosum, and Rhizopus
stolonifer. Yeast was also involved in the deterioration
of dates. A. niger was the most common fungus associ-
ated with the dates. Kader (2007) reported that microbial
spoilage of dates ( Ta m a r stage) can be caused by yeasts,
molds, and bacteria and that spoilage can be controlled by
drying the dates to 20% moisture or lower and by main-
taining the recommended temperature and relative humidity
ranges throughout the handling system.

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MICROBIAL CONTAMINATION
AND SPOILAGE OF DATES
The intensity of microbiological activity in a stored crop is
largely determined by the water activity ( a w ). Dates with
lower sugar content (e.g., immature dates) will have high
a w . This poses a technical difficulty for dates with moisture
content in the border line of their storability, which might
deteriorate due to micro flora activity because of the high a w
(Navarro, 2006). The micro flora of date fruit depends on the
maturation stage. Microbial counts are high at the first stage
of maturation ( Kimri ) and increase sharply at the Rutab
stage, then decrease significantly at the final dried stage of
maturation. Yeasts and molds are generally considered to
be spoilage organisms of date fruit and range from 1.7 to
7.2 log cfu/g at Rutab stage. Yeasts and mold counts are
higher than bacterial counts in dates. Lactic acid bacteria

Spoilage in Rutab stage
Rutab is preserved by refrigeration and freezing. Refrig-
eration can keep Rutab from microbial spoilage for days
only, while freezing can keep the product for longer time,