Water activity has historically been and continues to be recognised as a key concept in the area of food science. Despite its ubiquitous utilisation, it still appears as though there is confusion concerning its molecular basis, even within simple, single component solutions. Here, by close examination of the well-known Norrish equation and subsequent application of a rigorous statistical theory, we are able to shed light on such an origin. Our findings highlight the importance of solute-solute interactions thus questioning traditional, empirically based “free water” and “water structure” hypotheses. Conversely, they support the theory of “solute hydration and clustering” which advocates the interplay of solute-solute and solute-water interactions but crucially, they do so in a manner which is free of any estimations and approximations.

Large quantities of food are wasted globally. Sugars such as monosaccharides and oligosaccharides are valuable carbohydrate compounds that can be hydrolyzed from food waste, particularly from carbohydrate-rich bakery waste. These sugars can be extracted from the waste as a value-added compound for manufacturing other food products. Sub-critical water treatment is a new and emerging extraction technique that is considered as a green extraction technology. Water at high temperature and pressure can be used to hydrolyze and extract the sugars. This paper reviews (1) the general process for producing sugars from food wastes, (2) recovery of sugar (particularly oligosaccharides) from food waste via sub-critical water treatment, and (3) the potential of bakery waste as the resources of sugar recovery.

The objective of this research was to study the effect of water activity and glass transition temperature on the fat hydrolysis in a food model system. The model system was prepared with tapioca starch, casein, palm oil and sugar as 58, 14, 16 and 12 g/100 g model matrix, respectively. Hydrolysis reaction was accelerated bycommercial lipase at six levels of water content and water activity. Moisture sorption isotherm was obtained using isopiestic method while monolayer value was determined by BET equations. Glass transition temperature was determined from amorphous ingredients of starch and casein. Hydrolysis reaction showed a significantincrease above the monolayer value at 3.55 g water/100 g solid and aw 0.19. Hydrolysis occurred even at the glassy state of the model system. The role of water in the hydrolysis reaction is more related to the water activity concept rather than glass transition concept.

The availability of fresh water and the quality of aquatic ecosystems are important global concerns, and agriculture plays a major role. Consumers and manufacturers are increasingly sensitive to sustainability issues related to processed food products and drinks. The present study examines the production of sugar from the growing cycle through to processing to the factory gate, and identifies the potential impacts on water scarcity and quality and the ways in which the impact of water use can be minimised. We have reviewed the production phases and processing steps, and how calculations of water use can be complicated, or in some cases how assessments can be relatively straightforward. Finally, we outline several ways that growers and sugar processors are improving the efficiency of water use and reducing environmental impact, and where further advances can be made. This provides a template for the assessment of other crops.