Beyond water activity: Recent advances based on an alternative approach to the assessment of food quality and safety

Abstract

Water, the most abundant constituent of natural foods, is a ubiquitous plasticizer of most natural and fabricated food ingredients and products. Many of the new concepts and developments in modern food science and technology revolve around the role of water, and its manipulation, in food manufacturing, processing, and preservation. This article reviews the effects of water, as a near-universal solvent and plasticizer, on the behavior of polymeric (as well as oligomeric and monomeric) food materials and systems, with emphasis on the impact of water content (in terms of increasing system mobility and eventual water "availability") on food quality, safety, stability, and technological performance. This review describes a new perspective on moisture management, an old and established discipline now evolving to a theoretical basis of fundamental structure-property principles from the field of synthetic polymer science, including the innovative concepts of "water dynamics" and "glass dynamics". These integrated concepts focus on the non-equilibrium nature of all "real world" food products and processes, and stress the importance to successful moisture management of the maintenance of food systems in kinetically metastable, dynamically constrained glassy states rather than equilibrium thermodynamic phases. The understanding derived from this "food polymer science" approach to water relationships in foods has led to new insights and advances beyond the limited applicability of traditional concepts involving water activity. This article is neither a conventional nor comprehensive review of water activity, but rather a critical overview that presents and discusses current, usable information on moisture management theory, research, and practice applicable to food systems covering the broadest ranges of moisture content and processing/storage temperature conditions.

Quality of granola prepared with dried caju-do-cerrado (Anacardium othonianum Rizz) and baru almonds (Dipteryx alata Vog)

“…The levels of water activity related to the available water in the food were lower than 0.6, the maximum recommended for cereal-based foods to increase shelf life (Slade and Levine 1991). Baru almond influenced the protein and lipid content of Cerrado-fruit granola (CFG) due to the higher protein and lower fat content of these almonds (257.6 and 403.1 g/kg, respectively), compared with cashew nuts (229.3 and 465.4 g/kg) and Brazil nuts (164.5 and 635.2 g/kg) in the control granola (CG).…”

Análise das propriedades mecânicas de cereais matinais com diferentes fontes de amido durante o processo de absorção de leite

“…Entre os fatores de aceitabilidade, a textura aparece como um fator extremamente importante em alimentos do tipo crocante e extrusado. A característica de crocância está associada a frescor e qualidade do produto [32] e a sua perda, caracterizada pelo amolecimento é uma das causas de rejeição de consumo [29,30,31]. Inúmeras metodologias instrumentais e sensoriais têm sido utilizadas para descrever e definir as propriedades de textura de produtos a base de cereais [3,11,13,16,20,33,35].…”

“…É importante observar que a realização de ensaios em quintuplicatas visa a diminuição de do em estudos realizados sobre a influência da atividade de água nas propriedades mecânicas de alguns produtos derivados de cereais. O aumento da atividade de água promove uma aparente diminuição da rigidez e do ponto de quebra, devido ao efeito de plasticização da água [6,12,26,29,30]. O efeito crítico da umidade pode ser associado ao mecanismo de plasticização consistindo em um aumento no volume livre, devido à adição de moléculas de baixo peso molecular (água), resultando em uma maior mobilidade e aumento da flexibilidade das macromolé-culas [10,28].…”

Inhibition of Ice Crystal Growth in Ice Cream Mix by Gelatin Hydrolysate

“…Temperature fluctuations during storage and handling of frozen foods promote ice crystal growth. The crystal growth rate is very slow at lower storage temperatures, especially when the product is stored below its glass transition temperature (9)(10)(11). For ice cream, the glass transition temperature is typically in the range of -30 to -40°C, depending on the sugar ingredient used (12).…”