Fruit temperature

Table VI) may be a consequence of generally higher fruit temperature. Other factors may be operative. 

In desert areas of southern California fruit are often injured but leaves are seldom injured by sulfur dust. In coastal areas fruit burn is less marked but leaf burn may be acute. Where the air-vapor density is high, leaf temperatures in the sun may sometimes become higher than fruit temperatures. The leaf, a better absorber of radiation and a better radiator than the fruit, has a higher surface-mass ratio and appears to be very sensitive to the heat trap effect of high vapor density its temperature changes with great rapidity, but fruit temperature may lag until the danger period is passed (18). 

Controllable factors are desirable in experimental situations because their effects can usually be relatively easily and unambiguously detected and evaluated. Examples of individual controllable factors include x, yeast, fruit, temperature, concentration, time, amount, number, and size. 

To return to practical vinifioation—the method of treating the produce of the vine in fermentation differs with the climate, season, nature of the fruit, temperature of the vineyard, soil, mode of culture and fancy of tile proprietor, who is often guided by local custom. In some places the wine is not suffered to remain in the... 

Figure 5.3. A. change of second-derivative spectra of intact fruits due to fruit temperatures. B. difference spectra on the basis of 20.

Table 1836. Minimal O2 and maximtil CO2 concentrations in the atmosphere during storage of fruits (temperature 0-5 °C)...

While theoretical compressor power requirements are reduced slightly by going to lower evaporating temperatures, the volume of vapor to be compressed and hence compressor size and cost increase so rapidly that low-temperature operation is more expensive than high-temperature operation. The requirement of low temperature for fruit-juice concentration has led to the development of an evaporator... 

Figure 3.7 shows some early examples of this type of analysis (39), illustrating the GC determination of the stereoisomeric composition of lactones in (a) a fruit drink (where the ratio is racemic, and the lactone is added artificially) and (b) a yoghurt, where the non-racemic ratio indicates no adulteration. Technically, this separation was enabled on a short 10 m slightly polar primary column coupled to a chiral selective cyclodextrin secondary column. Both columns were independently temperature controlled and the transfer cut performed by using a Deans switch, with a backflush of the primary column following the heart-cut. 

Figure 10.2 MDGC-MS differentiation between the enantiomers of theaspiranes in an aglycone fraction from puiple passion fruit DB5 pre-column (25 m X 0.25 mm i.d., 0.25 p.m film thickness canier gas He, 0.66 ml/min oven temperature, 60-300 °C at 10 °C/min with a final hold of 25 min) permethylated /3-cyclodextrin column (25 m X 0.25 mm i.d., 0.25 p.m film thickness canier gas He, 1.96 ml/min 80 °C isothermal for 20 min and then programmed to 220 °C at 2 °C/min). Reprinted from Journal of High Resolution Chromatography, 16, G. Full et al., MDGC- MS a powerful tool for enantioselective flavor analysis , pp. 642-644, 1993, with permission from Wiley-VCH.

The Diels-Alder reaction was thought for many years to be only slightly influenced by catalysts. However, in 1960, Yates and Eaton (6) clearly demonstrated that with certain dienophiles, the presence of a molar equivalent of aluminum chloride can cause a remarkable acceleration of the reaction. Providing the diene is not polymerized (7) or otherwise destroyed by the catalyst, the modification can be fruitfully employed to carry out the reaction at lower temperature and for shorter times. 

As a general rule, foods which are not to be frozen are handled and stored at a temperature just above their freezing point, providing this does no damage (exceptions are fruits such as bananas and lemons). Produce which is to be frozen must be taken down below the freezing point of the constituents. Since foodstuffs contain salts and sugars, the freezing process will continue down to -18°C and lower. 

Frozen fruit and vegetables will be sealed in plastic bags and stored at -18°C or lower. The humidity at this temperature is not important. 

Because of their highly perishable nature, frozen fruits and vegetables are very sensitive to mishandling during distribution, especially in connection with maintaining proper conditions of temperature. 

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