ABSTRACT
The aim of this work was to develop a methodology to calculate the cooling curve for the sweetened condensed milk with added whey powder production and to assess the cooling regime effect on the distribution of lactose crystals' size and their microstructure. It is proposed to use a two-stage cooling curve. At the first stage, the cooling is carried out at a high speed, and at the second with a speed that varies depending on the rate of lactose crystallization. Electron microscopic studies have confirmed the cooling regime effect on the crystals' microstructure. The practical use of the developed regime showed that the two-stage cooling regime allows to reduce the size of lactose crystals (P < 0.05) and improve the quality of the finished product.
Subject(s)
Lactose/chemistry , Milk/chemistry , Animals , Crystallization , Food Analysis , Food Handling , Sweetening Agents , Temperature , Whey/chemistry , Whey Proteins/chemistryABSTRACT
The methods for determination of freezing point include cooling curve cryoscopy and air humidity cryoscopy. These methods are usually influenced by many factors, such as instrumentation, environment and operators. Despite the numerous experimental methods, precise freezing point values are challenging to obtain due to time-consuming procedures, limited sample size and extensive manual work. In this study, a semi-empirical hydration model (SEHM) was developed to calculate freezing point of NaH2PO4-K2HPO4 mixed electrolyte solution. According to SEHM, the water activity of mixed electrolyte solution was calculated by molality of solutes. Then the freezing point of solution was calculated. The calculated results were compared with those obtained by cooling curve cryoscopy and air humidity cryoscopy. The results indicate that the SEHM calculations are comparable to the measurements of cooling curve cryoscopy and air humidity cryoscopy.
ABSTRACT
This study aimed to analyze skimmed milk powder (SMP) and fructose in a new cooling curve to freeze boar semen. A total of 49 semen samples from seven boars were cryopreserved using the new curve with addition of glucose and fructose to the refrigerating diluents: Beltsville Thawing Solution (BTS + G; BTS + F) and Skimmed milk powder (SMP + G; SMP + F), totaling four experimental groups for analysis. To finish the curve, aliquots of semen were packaged in 0.5 ml straws and kept in liquid nitrogen. During the cooling curve, SMP mean spermatic vigor and motility were greater than the BTS (p < 0.05). After thawing, a decrease of spermatic force and motility in both extenders was observed, where the BTS presented spermatic vigor (2.1 ± 0.55) and motility (38 ± 21.8), presenting better results (p < 0.05). There was no statistical difference between sugars added to the BTS and SMP in spermatic force and motility (p > 0.05), although the use of fructose allowed an equalization of motility between the SMP and BTS (p > 0.05). Functionality of membrane was better preserved with the addition of fructose, in both extenders. The rate of sperm viability was significantly higher in extender containing glucose and SMP (71.8 ± 12.5). The percentage of intact acrosome was higher on the treatment containing glucose, independent of the extender (BTS + G: 81.8 ± 7.2, SMP + G: 81.4 ± 14.2). To conclude, the results suggest that the BTS is still the best option to cryopreserve and fructose could be used in boar semen cryopreservation in new cooling curve.(AU)
O presente trabalho analisou o emprego do leite em pó desnatado (LPD) adicionado de frutose em uma nova curva de resfriamento para criopreservação de sêmen suíno. Um total de 49 ejaculados, de sete varrões foram criopreservados utilizando a nova curva de resfriamento com glicose e frutose adicionada aos diluentes Beltsville Thawing Solution (BTS + D; BTS + F) e Leite em pó desnatado (LPD + D; LPD + F), totalizando quatro grupos experimentais para análises. Ao final da curva, as alíquotas de sêmen foram envasadas em palhetas de 0,5 mL e mantidas em nitrogênio líquido. Durante a curva de resfriamento, a média de vigor e motilidade espermática do LPD foi maior do que do BTS (p < 0.05). Após descongelação, observou-se queda do vigor e motilidade em ambos diluentes, com o BTS apresentando melhores resultados de vigor (2,1 ± 0,55) e de motilidade (38 ± 21,8) (p < 0,05). Entretanto, o uso da frutose permitiu equiparação dos valores da motilidade entre LPD e BTS (p > 0,05). A funcionalidade de membrana foi melhor preservada com adição da frutose, em ambos os diluentes. Os dados de vitalidade espermática foram significativamente maiores no diluente contendo glicose e LPD (71,8 ± 12,5). A porcentagem de acrossomas intactos foi maior no tratamento que continha glicose, independentemente do diluente utilizado (BTS + G: 81,8 ± 7,2, SMP + G: 81,4 ± 14,2). Os resultados obtidos indicaram que o BTS, ainda é a melhor opção de criopreservação e que a frutose pode ser utilizada para criopreservação de sêmen de varrão na nova curva de resfriamento.(AU)
