Estabilidade Do Leite Ao Álcool Ainda Pode Ser Um Indicador Confiável?

Abstract

ResumoAs provas de estabilidade alcoólica e acidez Dornic ainda são amplamente utilizadas em diversos países, mensurando indiretamente a qualidade microbiológica do leite. Porém, outros fatores além da contagem de micro-organismos alteram essa relação, causando um efeito confundidor nesses testes de triagem. O objetivo deste estudo foi relacionar o pH, a contagem bacteriana total, a acidez Dornic e a porcentagem de lactose em leites estáveis e instáveis ao álcool. Foram analisadas 322 amostras de leite, sendo classificadas em ácidas, normais ou instáveis não ácidas, segundo os testes de resistência alcoólica e acidez titulável. Diferentemente de leites normais ou ácidos, não existe relação entre pH, CBT e acidez Dornic em amostras de leite que possuem instabilidade alcoólica sem acidez adquirida. Nesse tipo de leite, valores de pH entre 6,6 e 6,8 são acompanhados de contagens bacterianas mais baixas, de até 10 5 bac.mL -1 , e porcentagens de lactose mais altas, de até 4,5%. Conforme a CBT aumenta, a porcentagem de lactose ou o pH tendem a diminuir, porém não necessariamente juntos. Esse comportamento faz com que o teste do álcool não seja um indicador confiável para a qualidade do leite, devendo ser aplicado sempre em conjunto com outras provas que auxiliem no diagnóstico de acidez bacteriana e/ou resistência térmica, como titulação do ácido lático, mensuração de pH e teste da fervura. Palavras-chave: alizarol; etanol; instabilidade. AbstractThe alcoholic stability of milk is a current problem in many countries that still use the alcohol test to measure the microbiological quality of milk. Beyond microbiological acidity, many factors can also affect the alcoholic stability of milk, leading to a confounding effect in alcohol test and industrial losses. The present study aimed to evaluate the relationship between pH, bacterial count, Dornic acidity, lactose percentage and ethanol stability of milk. The samples comprised fresh raw milk from 322 dairy farms from Parana state. According to the results of the 72º ethanol test and the Dornic acidity test, the samples received the following classification: stable milk, acidic milk, or unstable milk to ethanol. There was no relationship among pH, Dornic acidity and microbiological count in samples of milk that were unstable to alcohol test. Unstable milk to ethanol has pH values ranging between 6.6-6.8 with low microbiological count (less than 10 5 cell.mL -1 ) and higher lactose percentages (up to 4.5%). As bacterial count increase, the lactose percent tends to decrease, but not necessarily together. This feature makes the alcohol test unreliable, and the use of other parameters

Multifactorial analysis of unstable non-acid milk occurrence in dairy production/ Análise multifatorial da ocorrência de leite instável não ácido em propriedades leiteiras

“…There was a difference (P<0.05) for the qualitative characteristics of the farms' milk between the Stable and UNAM for titratable acidity (Table 3), with higher values for the Stable units. This result confirms that UNAM's instability is not exclusively related to greater acidity (SOUZA et al, 2016;MACHADO et al, 2017) being yet another indicator that UNAM can be used for specific processing (FAGNANI et al, 2016a). As expected, most of the milk components were not changed when the milk was classified as UNAM (SOUZA et al, 2016).…”

“…Alcohol testing is an indirect way of trying to identify acidity of microbiological origin (FAGNANI et al, 2016a), but it is also influenced by other factors, especially those of feed origin that can alter the composition of milk, such as the salt balance, lactose content, urea nitrogen and ionic calcium (SOUZA et al, 2016).…”

“…The prediction of thermal stability in milk protein using a quick estimation process through milk ethanol stability is still widely used in Brazilian dairy industries, as a way to obtain a high-quality raw milk (RATHNAYAKE et al, 2016), due to its lower bacterial contamination (FAGNANI et al, 2016a).…”

<b>Physical and chemical characteristics of milk from goats supplemented with different levels of total digestible nutrients in the dry period

“…According to the aforementioned, there is a possibility of variation of the data found for the milk acidity, resulting from the possible reduction in lactose concentration in the milk due to the advancement of the lactation curve and that added to the information that this sugar is fermented by microorganisms that transform a lactose molecule into 4 molecules of lactic acid (Kondyli, Svarnas, Samelis, & Katsiari, 2012;Fagnani, Battaglini, Beloti, & Araújo, 2016), which may be one of the possible explanations for the acidity variation along the collections. This is a parameter that is directly linked to the milk storage, so the Brazilian legislation in the normative instruction number 37 as of 2000, accepts that raw frozen milk has a higher acidity variation than raw milk without freezing, thus all samples of the treatments presented acidity (Table 2) within the acceptable range by the aforementioned legislation.…”

“…The microorganisms, when carrying out the fermentation, transform a molecule of lactose into 4 molecules of lactic acid, thus increasing the quantity of dissolved particles and causing a decrease in the cryoscopic index (Fagnani et al, 2016).…”