Tahini is made by grinding sesame, and oil rising to the top is its natural tendency: an oil layer forms above, a dry, hard mass below, the container gets soiled and the texture turns rough. In tahini halva the same separation is a core quality problem, and customers often treat the product as spoiled and return it.
The effect of temperature is not a straight line. In a 180-day study commercial sesame pastes were kept at 4 °C, at room temperature (average 20.5 °C) and at 40 °C; particles grew with temperature, while oil separation was highest at room temperature, which the authors ascribed to temperature fluctuation. Against a peroxide limit of 19.7 meq O2/kg, the longest recommended storage times were:
| Storage temperature | Maximum |
|---|---|
| 40 °C | 30 days |
| Room temperature | 60 days |
| 4 °C | 120 days |
Halva does not soften; it firms up and sheds oil: in a study storing tahini halva at 20, 30 and 40 °C, penetration force rose with temperature and time, and appearance, texture and flavour scores fell. So monitor shelves that warm by day and cool by night, such as those under a roof, separately: place a logger on an upper and a lower shelf, tie each batch to its lot, and follow the storage condition on the pack label.