Freezing is the most common method used to preserve and minimize loss in quality of catfish during storage. Since freezing is a heat transfer process, the design and selection of freezing equipment require knowledge o...Freezing is the most common method used to preserve and minimize loss in quality of catfish during storage. Since freezing is a heat transfer process, the design and selection of freezing equipment require knowledge of thermophysical properties such as freezing temperature, enthalpy of freezing, unfreezable water and specific heat. Channel catfish thermophysical properties at freezing temperature were determined using differential scanning calorimetry. Using the combination of Raoult＇s law and Classius-Clapeyron equations, the amount of unfreezable （bound water） was estimated to be 0.129 g H20 g^-1 During freezing （or melting）, the specific heat increased from about 1.5 J g^-1 ℃^-1 to about 30.6 J g^-1 ℃^-1 It was found that freezing of catfish occur over a wide temperature range with the peak and incident freezing temperatures occurring at temperatures of-1.88 ℃ and -6.10 ℃, respectively. About 250 J g^-1 of heat have to be removed from catfish when it is to be frozen to -40 ℃. The implication is that any system that will be designed to freeze catfish must be able to remove 250 J g^-1 of heat.展开更多
Vernonia amygdalina Del. is a tropical species susceptible to frost which is an annual phenomenon of the winter season of the Eastern Cape. Limited populations of the species arc in the province dieback during the win...Vernonia amygdalina Del. is a tropical species susceptible to frost which is an annual phenomenon of the winter season of the Eastern Cape. Limited populations of the species arc in the province dieback during the winter period, thereby making large scale cultivation through conventional vegetative propagation impossible. In our effort to increasing the population of the species within the province, a micropropagation approach through tissue culture teehnology was employed. Two growth regulators （BAP ＆ NAA） were tested at four levels of concentration under continuous light and dark conditions. Plantlets were subsequently transferred to the field after acclimatization at different temperature conditions. The result of the study showed that BAP generally performs better than NAA for callus induction under continuous darkness, while direct micropropagation of shoot under continuous light condition at I mg L^-1BAP showed the best result. To achieve greater success for the rapid multiplication of the species, this study further demonstrates that the optimum temperature range for acclimatizing the species prior to the transfer of the plantlet to the field is between 23 ±3 ℃.展开更多
文摘Freezing is the most common method used to preserve and minimize loss in quality of catfish during storage. Since freezing is a heat transfer process, the design and selection of freezing equipment require knowledge of thermophysical properties such as freezing temperature, enthalpy of freezing, unfreezable water and specific heat. Channel catfish thermophysical properties at freezing temperature were determined using differential scanning calorimetry. Using the combination of Raoult＇s law and Classius-Clapeyron equations, the amount of unfreezable （bound water） was estimated to be 0.129 g H20 g^-1 During freezing （or melting）, the specific heat increased from about 1.5 J g^-1 ℃^-1 to about 30.6 J g^-1 ℃^-1 It was found that freezing of catfish occur over a wide temperature range with the peak and incident freezing temperatures occurring at temperatures of-1.88 ℃ and -6.10 ℃, respectively. About 250 J g^-1 of heat have to be removed from catfish when it is to be frozen to -40 ℃. The implication is that any system that will be designed to freeze catfish must be able to remove 250 J g^-1 of heat.
文摘Vernonia amygdalina Del. is a tropical species susceptible to frost which is an annual phenomenon of the winter season of the Eastern Cape. Limited populations of the species arc in the province dieback during the winter period, thereby making large scale cultivation through conventional vegetative propagation impossible. In our effort to increasing the population of the species within the province, a micropropagation approach through tissue culture teehnology was employed. Two growth regulators （BAP ＆ NAA） were tested at four levels of concentration under continuous light and dark conditions. Plantlets were subsequently transferred to the field after acclimatization at different temperature conditions. The result of the study showed that BAP generally performs better than NAA for callus induction under continuous darkness, while direct micropropagation of shoot under continuous light condition at I mg L^-1BAP showed the best result. To achieve greater success for the rapid multiplication of the species, this study further demonstrates that the optimum temperature range for acclimatizing the species prior to the transfer of the plantlet to the field is between 23 ±3 ℃.
