Temperature can play a significant role in the development of wine at many stages during its lifetime. Elevated temperature, however, poses a significant risk to the sensory attributes of wine and its resultant shelf-life. Wines often experience difficult environmental conditions during transport and storage, and this can directly impact on the colour, aroma and mouthfeel of the wine. Higher and/or fluctuating temperature can essentially accelerate the ageing process. Unfortunately, these changes often go unnoticed until the wine reaches the consumer. Numerous studies have investigated the impact of elevated temperature on wines, with noticeable effect, such as reduction of sulfur dioxide, colour development (especially browning of white wines) and changes in the profile of volatile compounds, being common. Unfortunately, most of these studies tend to have a narrow scope and tend to focus only on a limited number of wine types or on specific compounds. The chemistry changes involved in heat-affected red wines are generally more complex than they are in white wines, but it is arguable that white wines are more sensitive to the effect of heat and therefore require the same or a greater level of research consideration with respect to temperature effects. The focus of this review is to highlight the common effects that different wine types and styles can experience when subjected to elevated storage temperature that are considered to be beyond the limits that most winemakers and consumers would accept. This review will also summarise the fundamental chemical kinetics that play a significant role in wine development at elevated temperature.

Field tests to evaluate in-line dosing with bentonite followed by centrifugation as an alternative to batch fining for protein haze control in white wine or juice were undertaken. The tests were performed at a commercial winery with a Sultana wine and Gordo (Muscat of Alexandria) juice and using two types of bentonite: Vitiben and SIHA-Active-Bentonite G. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration decreased to stable values between 30 s and 2 min after bentonite injection. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests detected no difference between untreated, in-line dosed, and batch fined wine. Furthermore the volume of wine or juice occluded in lees can be substantially reduced by centrifugal compaction. However, incomplete separation of bentonite from wine or juice during centrifugation produced a carryover of 30% of the added bentonite into the clarified wine. This carryover problem may be mitigated, inter alia, by reducing operating flowrate through the centrifuge or using multiple centrifugation steps (in parallel or series). Therefore, inline dosing followed by centrifugation provides a rapid processing method for protein haze reduction in wine or juice with a decreased volume of lees. It can reduce significant value losses presently arising in the wine industry from batch fining and the resulting quality downgrades that occur in wine recovered from bentonite lees by rotary drum vacuum filtration.Abbreviations ACN acetonitrile; AS Australian Standard; BSA bovine serum albumin; cyt. c cytochrome C; NTU nephelometric turbidity units; OLS ordinary least-squares; RDVF rotary drum vacuum filtration;Re Reynolds number; SSE sum of the square of the errors; TFA trifluoroacetic acid

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