Influence of Proteolysis on the Binding Capacity of Flavor Compounds to Myofibrillar Proteins

Proteolysis occurs extensively during postmortem aging, enzymatic tenderization and fermentation of meat products, whereas less is understood regarding how proteolysis affects meat flavor. Myofibrillar proteins (MP) were extracted from beef longissimus dorsi muscle and subsequently treated with three commercial proteases. The effect of proteolysis on the interactions between the treated MP and butyraldehyde, 2-pentanone, octanal and 2-octanone was investigated. The progress of proteolysis increased the degree of hydrolysis (DH) and the surface hydrophobicity but decreased the turbidity and particle size. Fluorescence-quenching analysis results indicated that the enzymatic treatment generally increased the quenching constant (Ksv) between the treated MP and ketones but decreased the Ksv between the treated MP and aldehydes, and the papain treatment changed the Ksv value to a larger degree than treatment with proteinase K and bromelain. The adsorption assay showed that the proteinase K treatment largely increased the adsorption capacity of the MP to octanal (by 15.8–19.3%), whereas the bromelain treatment significantly reduced the adsorption capacity of the treated MP to butyraldehyde (by 6.0–7.9%) and 2-pentanone (by 9.7–11.9%). A correlation analysis demonstrated a strong positive correlation (0.859, p < 0.05) between the DH of the MP and the adsorption ability of the treated MP to octanal. This study highlighted the significant but complex influence of proteolysis on MP binding capacity to flavor compounds

Multidrug- Resistant Atypical Variants of Shigella flexneri

We identified 3 atypical Shigella flexneri varieties in China, including 92 strains with multidrug resistance, distinct pulse types, and a novel sequence type. Atypical varieties were prevalent mainly in developed regions, and 1 variant has become the dominant Shigella spp. serotype in China. Improved surveillance will help guide the prevention and control of shigellosis. Each year worldwide, ≈1.5 million children <5 years of age die from diarrheal diseases (1), which is of particular concern in developing countries. Shigella spp. are leading bacterial causes of diarrhea, responsible for>80 million cases of bloody diarrhea and 700,000 deaths each year (2), and S. flexneri serotype 2a has been recognized as the most prevalent serotype in China for many years (3). To better understand the etiology of bacterial diarrhea in China and to determine if S. flexneri serotype 2a is still the most prevalent serotype in China, we conducted a study during May 2008–December 2010. The Study A total of 10,021 fecal samples were obtained from patients with diarrhea or dysentery at hospitals in 8 provinces within the eastern, southern, western, northern, an