Isolation and characterisation of a heat-resistant peptidase from Pseudomonas panacis withstanding general UHT processes

Baur, Claudia; Krewinkel, Manuel; Kutzli, Ines; Kranz, Bertolt; Neubeck, Mario von; Huptas, Christopher; Wenning, Mareike; Scherer, Siegfried; Stoeckel, Marina; Hinrichs, Jörg; Stressler, Timo; Fischer, Lutz

doi:10.1016/j.idairyj.2015.04.009

Cited by 40 publications

(73 citation statements)

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“…The levels of psychrotrophic bacteria in the raw milk immediately after collection is low, but storage under refrigerated conditions will promote their growth, and these organisms can produce extracellular heat‐resistant proteases and lipases (Adams, Barach, & Speck, ; Barach et al., ; Baur et al., ; Dufour et al., ; Hantsis‐Zacharov & Halpern, ; McKellar, ; Mitchell et al., ; Stevenson et al., ; von Neubeck et al., ; West et al., ). It has been reported that the production of heat‐stable proteinases occurs late in the exponential growth phase of the bacteria (Adams et al., ; Guinot‐Thomas et al., ; Law, Andrews, & Sharpe, ; Matselis & Roussis, ; Nieuwenhuijse & van Boekel, ; Stoeckel et al., ) and, therefore, these proteinases should not be present in UHT milk products prepared from good‐quality milk.…”

Section: Age Gelationmentioning

confidence: 99%

Age Gelation, Sedimentation, and Creaming in UHT Milk: A Review

Anema

2018

Comp Rev Food Sci Food Safe

100

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Demand for ultra‐high‐temperature (UHT) milk and milk protein‐based beverages is growing. UHT milk is microbiologically stable. However, on storage, a number of chemical and physical changes occur and these can reduce the quality of the milk. These changes can be sufficiently undesirable so as to limit acceptance or shelf life of the milk. The most severe changes in UHT milk during storage are age gelation, with an irreversible three‐dimensional protein network forming throughout, excessive sedimentation with a compact layer of protein‐enriched material forming rapidly at the bottom of the pack, and creaming with excessive fat accumulating at the top. For age gelation, it is known that at least two mechanisms can lead to gelation during storage. One mechanism involves proteolytic degradation of the proteins through heat‐stable indigenous or exogenous enzymes, destabilizing milk and ultimately forming a gel. The other mechanism is referred to as a physico‐chemical mechanism. Several factors are known to affect the physico‐chemical age gelation, such as milk/protein concentration, heat load during processing (direct compared with indirect UHT processes), and milk composition. Similar factors to age gelation are known to affect sedimentation. There are relatively few studies on the creaming of UHT milk during storage, suggesting that this defect is less common or less detrimental compared with gelation and sedimentation. This review focuses on the current state of knowledge of age gelation, sedimentation, and creaming of UHT milks during storage, providing a critical evaluation of the available literature and, based on this, mechanisms for age gelation and sedimentation are proposed.

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Section: Age Gelationmentioning

confidence: 99%

Age Gelation, Sedimentation, and Creaming in UHT Milk: A Review

Anema

2018

Comp Rev Food Sci Food Safe

100

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“…At elevated temperatures higher than 30 °C, as shown in Figure , the growth rate of pseudomonads decreases with increasing temperature, whereas the AprX activity increases until reaching its maximum at around 45 °C after which it decreases rapidly until reaching its autolysis temperature at around 55 °C (Baur et al., ; Dufour et al., ).…”

Section: Biological Properties Of Protease Aprxmentioning

confidence: 98%

“…() observed greater expression of AprX produced by P. fluorescens 07A in 10% (w/v) sterile reconstituted skim milk at 12 hr when the strain was in the lag phase at 4 and 10 °C, than when the logarithmic and stationary phases were reached. The early production of AprX may be closely associated with the low enzymatic activity at low temperatures (Baur et al., ; Dufour et al., ; Zhang et al., ). To effectively utilize the nutrients in the medium and realize proliferation, pseudomonads probably compensate for the decreased activity with greater AprX production.…”

Section: Biological Properties Of Protease Aprxmentioning

confidence: 99%

“…Inhibitors for amino‐acid‐specific proteases: as a metalloprotease, the activity of AprX is only negligibly affected by the inhibitors of aspartyl protease (pepstatin A), serine protease (PMSF and benzamidine), and cysteine peptidases (E‐64) (Alves, Salgado, Eller, Vidigal, & de Carvalho, ; Baur et al., ).…”

Section: Biological Properties Of Protease Aprxmentioning

confidence: 99%

“…Compared with the TNBS assay, the reagents used in the OPA method are more stable and less toxic (Nielsen, Petersen, & Dambmann, ). Therefore, the OPA method has been more frequently used in detecting AprX activity (Baur et al., ; Stoeckel et al., ). Another approach is determining the breakdown of an external substrate.…”

Section: Detection Of Aprxmentioning

confidence: 99%

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The Extracellular Protease AprX from Pseudomonas and its Spoilage Potential for UHT Milk: A Review

Zhang

Bijl

Svensson

et al. 2019

Comp Rev Food Sci Food Safe

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The negative effects of proteases produced by psychrotrophic bacteria on dairy products, especially ultra‐high‐temperature (UHT) milk, are drawing increasing attention worldwide. These proteases are especially problematic, because it is difficult to control psychrotrophic bacteria during cold storage and to inactivate their heat‐resistant proteases during dairy processing. The predominant psychrotrophic species with spoilage potential in raw milk, Pseudomonas, can produce a thermostable extracellular protease, AprX. A comprehensive understanding of AprX on the aspects of its biological properties, regulation, proteolytic potential, and its impact on UHT milk can contribute to finding effective approaches to minimize, detect, and inactivate AprX. AprX also deserves attention as a representative of all extracellular metalloproteases produced by psychrotrophic bacteria in milk. The progress of current research on AprX is summarized in this review, including a view on the gap in current understanding of this enzyme. Reducing the production and activity of AprX has considerable potential for alleviating the problems that arise from the instability of UHT milk during shelf‐life.

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