Strategies for raw sheep milk storage in smallholdings: Effect of freezing or long-term refrigerated storage on microbial growth

Autor(es)

Tribst, A. A. L. ^[1] ; Falcade, I. L. T. P. ^[1] ; de Oliveira, M. M. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Ctr Food Studies NEPA, UNICAMP, Albert Einstein 291, BR-13083852 Campinas, SP - Brazil

^[2] Fed Ctr Technol Educ Celso Suckow Fonseca CEFET R, Voluntarios Patria 30, BR-27600000 Valenca - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF DAIRY SCIENCE; v. 102, n. 6, p. 4960-4971, JUN 2019.
• Citações Web of Science: 2

Resumo

We assessed the effects of freezing and refrigeration over long periods on the microbiological quality of sheep milk. The raw milk was frozen in 1-L plastic bags or 5-L milk buckets and, after 1 mo, thawed at 7 or 25 degrees C. We evaluated these samples immediately after thawing (d 0) and after 1 d of storage at 7 degrees C. Furthermore, we stored fresh raw milk at 7 degrees C for 10 d in the same packages and in a bulk milk cooler at 4 degrees C (adding 10% of fresh raw milk daily). The total bacterial, total psychrotolerant, and proteolytic psychrotolerant counts were evaluated before and after thawing (for previously frozen milk) and daily (for refrigerated milk). The frozen-thawed milks showed no significant increase in bacterial counts immediately after thawing for all samples (<0.7 log cfu/mL), but only the samples packaged in 1-L bags and thawed at 7 degrees C remained micro-biologically adequate after 1 d of storage. Findings of the refrigerated samples were modeled using a modified Gompertz equation, obtaining a lag phase of around 0.5 (5-L bucket), 2.6 (1-L bag), and 7.0 (bulk milk cooler) d for total bacterial and total psychrotolerant counts. Maximum growth rates (mu(max)) were 1.0 and 1.0 (5-L bucket), 1.2 and 1.3 (1-L bag) and 3.0 and 1.5 (bulk milk cooler) ln(cfu/mL) per day for total bacteria and total psychrotolerant counts, respectively. Compared with total bacteria and total psychrotolerant bacteria, psychrotolerant proteolytic bacteria grew slowly, reaching unacceptable counts only after 9 to 10 d of storage. The studied methods are interesting alternatives for preserving raw sheep milk on smallholdings. (AU)

• Processo FAPESP: 17/02832-4 - Congelamento/descongelamento de leite de ovelha: alterações induzidas no leite, alternativas para minimizar essas modificações e impacto na produção de iogurte
• Beneficiário: Alline Artigiani Lima Tribst
• Modalidade de apoio: Auxílio à Pesquisa - Regular