The effect of fat content on the rheology, microstructure and heat-induced functional characteristics of Cheddar cheese

Abstract

Cheddar cheeses with the different fat contents were made in triplicate and ripened at 4°C for 30 d and at 7°C for the remainder of the 180-d investigation period. The cheeses were designated: full-fat (FFC), 300 g kg⁻¹; reduced-fat (RFC), 219 g kg⁻¹; half-fat (HFC), 172 g kg⁻¹; and low-fat (LFC), 71.5 g kg⁻¹. A decrease in the fat content from 300 to ≤172 g kg⁻¹ resulted in significant (P<0.05) decreases in contents of moisture in non-fat substance and pH 4.6 soluble N (expressed as % total N), and increases in the contents of moisture, protein, intact casein and free amino acids. Reduction in fat content resulted in an increase in the volume fraction of the casein matrix and a decrease in the extent of fat globule clumping and coalescence. The mean values of fracture stress and firmness for the FFC were significantly lower than those of the RFC and HFC, which had similar values; the values for the LFC exceeded the limits of the test and were markedly higher than those of the other cheeses at all times. On baking the cheese, reduction in fat content resulted in significant increases in the mean melt time (time required for shred fusion) and apparent viscosity and a decrease in the mean flowability of the melted cheese. The stretchability of the FFC increased most rapidly and, at ∼15 and 30 d, attaining mean values which were significantly higher than those of the other cheeses. Thereafter the stretchability of the FFC decreased progressively to values that were significantly (i.e. at 150 d) or numerically (i.e., at 180 d) lower than those of the RFC and HFC. At ripening times ≥15 and ≤90 d, the stretchability of the LFC was significantly lower than that of the RFC, and significantly or numerically lower than the HFC.

Introduction

Recent market research suggests that reduction in fat content and delivery of desirable functionality are two of the major approaches by which international cheese consumption can be increased (Market Tracking International, 1998). Hence, many studies have investigated the effects of various treatments on the proteolysis, texture and microstructure of reduced-fat cheeses with a view to improving quality (Ardö, Larsson, Mansson & Hedenberg, 1989; Banks, Brechany & Christie, 1989; Tunick et al., 1993; Kucukoner & Haque, 1995; Bryant, Ustanol & Steffe, 1995; Desai & Nolting, 1995; Drake, 1997; Fenelon & Guinee, 1997; Guinee et al., 1998a). Comparatively few studies have investigated the heat-related functionality of reduced-fat cheese and the factors affecting it (Tunick, Mackey, Smith & Holsinger, 1991; Merrill, Oberg & McMahon, 1994; Tunick, Malin, Smith & Holsinger, 1995; McMahon, Alleyne, Fife & Oberg, 1996; Rudan, Barbano, Guo & Kindstedt, 1998a, Rudan, Barbano & Kindstedt, 1998b; Poduval & Mistry, 1999); the latter studies pertain mostly to Mozzarella. Furthermore, the effect of reducing fat content (e.g., from full-fat to half-fat) on the microstructure, proteolysis, texture and/or functionality of cheese has received little attention (Mistry & Anderson, 1993; Bryant et al., 1995; Mackey & Desai, 1995; Tunick & Shieh, 1995; Rudan et al., 1998a, Rudan et al., 1998b). In particular, little has been reported on the effect of incremental fat reduction on cheese functionality (Fife, McMahon & Oberg, 1996; Rudan & Barbano; 1998; Rudan, Barbano, Yun & Kindstedt, 1999), especially for cheeses other than Mozzarella, e.g., Cheddar (Olson & Bogenrief, 1995). The limited comparison between full- and half-fat Mozzarella has shown that fat reduction results in an increase in firmness and a decrease in the quantity of free oil exuded on baking and flowability.

The objective of the current study was to investigate the effects of incremental fat reduction, in the range 71–300 g kg⁻¹, on the composition, rheology, microstructure and functionality of Cheddar cheese.