A rheological approach to the quantitative assessment of Traditional Balsamic Vinegar quality

https://doi.org/10.1016/j.jfoodeng.2007.10.017Get rights and content

Abstract

This work aimed at evaluating the ability of rheological measurements to describe the quality of Traditional Balsamic Vinegars (TBV) with respect to their composition and sugar crystallization. With this aim, shearing experiments were conducted on 100 samples of TBV using a controlled-strain rotational rheometer, whereas the concentration of glucose, fructose, acetic acid, gluconic acid, malic acid as well as refractive index and titrable acidity were determined according to the normal procedure for quality assessment of TBV. A broad range for the rheological response was observed including Newtonian and shear-thinning behavior. A Joining Tree Cluster Analysis (JTCA) was able to classify the investigated vinegars into meaningful classes based on the stress data alone. Moreover, Principal Component Analysis (PCA) was performed to link composition data to rheological properties, and finally, Multivariate Regression Analysis (MRA) evaluated the contribution of the main constituents to vinegar viscosity. The results suggested that rheological analysis must be carried out in order to spot some fundamental aspects of the vinegar texture, which cannot be detected otherwise. In particular, two rheological parameters were proposed as objective and quantitative descriptors of TBV quality: the shear viscosity measured at 500 s−1 accounting for the vinegar composition, and the flow behavior index accounting for sugar crystallization.

Introduction

Traditional Balsamic Vinegars (TBV) from both Modena and Reggio Emilia have recently been acknowledged as a “Protected Designation of Origin” product (PDO) by the European Union (CE no. 813/2000, April 17, 2000). It is an ancient sauce from grape juice and aged for several years (Giudici and Rinaldi, 2007). The physical aspects of TBV, such as color and viscosity, are important parameters for quality assessment. Nevertheless no procedure has been established to date to determine these objectively.

There is long-term anecdotal evidence from vinegar producers that flow syrupiness and composition (mainly the glucose, fructose and acetic acid concentration) are the principal components in determining the overall quality of TBV. Unfortunately, objective procedures aimed at determining texture properties are neither recommended nor newly established in their production. Falcone et al. (2006) carried out a preliminary study dealing with the rheology of model system simulating TBV. These authors analyzed the effects of glucose, fructose and acetic acid on the shear viscosity and concluded that rheological measurements could be a simple and reliable method for rapid and objective evaluation of TBV quality before performing sensory analysis. However, no work has been published to date on the contribution made by the chemical constituents to vinegar texture. Recently, the standardization of texture measurements was decided in Europe, and sensory evaluation standard IS0 11036 was published. Specifically, it defines the procedure for measuring food viscosity. For other fluid, semi-fluid food products and beverages, the perceived viscosity is considered to be the most striking and clearly recognizable mouthfeel parameter (Bourne, 2002, Szczesniak, 1979), which influences the intensity of flavor (Godshall, 1997, Thomas et al., 1995;). Viscosity is also known to modify other oral sensations in wine, including saltiness, sweetness, bitterness, flavor and astringency (Christensen, 1980, Hollwood et al., 2002, Smith et al., 1996, Wendin et al., 1997). The perceived viscosity of liquid and semisolid foods is usually assessed either by oral methods based on the measurement of resistance to flow over the tongue surface, or by non-oral methods based on the measurement of the force required to manipulate the fluid in the mouth while sipping from a teaspoon (Langstaff et al., 1991). Moreover, due to the subjectivity of human perception and to the time required to train panel members, sensory analysis may be poorly reproducible and very expensive.

Another important concern relating to both the composition and viscosity must also be taken into account while assessing the procedures for evaluating TBV quality. Some studies proved that high concentration of both glucose and fructose could lead to a natural selection of fructosophilic yeasts, and therefore to an increase in the vinegar’s susceptibility to sugar crystallization (Giudici et al., 2004). These authors showed that the concentration of vinegars taking place during ageing allows the crystallization of glucose rather than fructose, giving rise to a structure affecting vinegar texture and appearance. It is well established that sugar crystallization from aqueous matrices depends mainly on the composition and viscosity. Even though the viscosity characteristics of a number of liquid foods have already been investigated (Christensen, 1979, Christensen and Casper, 1987, Houska et al., 1993, Shama and Sherman, 1973, Shama et al., 1973); and others regarding the crystallization (Assil et al., 1991, Bhandari et al., 1999a, Bhandari et al., 1999), studies on viscosity and crystallization of TBV are not available. In this context, we believe that knowledge of rheological properties should ideally provide objective information on the relationships between TBV composition and texture related properties including viscosity.

The main goal of this work was to demonstrate the enormous potential of rheology based approach to investigate TBV quality. In particular, the work focused on the ability of viscosity measurements to describe vinegar quality with respect to composition and the physical state of the main sugars.

Section snippets

TBV retrieval

One hundred samples of Traditional Balsamic Vinegars of Modena “TBVM” were kindly supplied by the producers’ consortium of Spilamberto (Modena, Italy), and then they were analyzed as received. For these vinegars, the producers claimed an ageing period of over 25 years. Twelve samples were selected because of their poor quality: they exhibited the presence of suspended solids both by visual inspection and tasting.

Rheological measurements

Rheological behavior of TBVM samples was studied by means of a controlled-strain

Flow experiments

Flow experiments provided a wide range of rheological responses among the investigated vinegars including the Newtonian and shear-thinning behavior. For the sake of the example, some mechanical spectra of the stress applied to the samples are represented in Fig. 1. As can be inferred from the figure, TBVM680, TBVM75, and TBVM827 samples showed a well-defined Newtonian behavior: a linear relationship between the applied shear rate and the generated shear stress was clearly observed and flow

Conclusions

The results of this study suggest that vinegar having different composition properties can show similar rheological behavior irrespective of the main chemical constituents. The presence of crystallized sugars in vinegars having similar sugar composition confirm the fact that other minor uninvestigated substances are able to influence vinegar structure and quality. On the other hand, some vinegar samples appearing free of sugar crystals by visual inspection showed shear-thinning rheological

Acknowledgement

The study presented in this paper is part of a greater scientific project “Use of different woods as a new approach to solve the over long bio-acetification processes” funded by European Commission (COOP-CT-2005-017269). The authors are grateful to the “Consorteria of Spilamberto” for sample retrieval and to the researcher group working at the Department of Chemical and Material Engineering of the University of Calabria; Bucci, I-87030 Rende (CS), Italy, for the rheological tests.

References (22)

  • B. Bhandari et al.

    A research note: Rheology of selected Australian honeys

    Journal of Food Engineering

    (1999)
  • P. Giudici et al.

    A theoretical model to predict the age of traditional balsamic vinegar

    Journal of Food Engineering

    (2007)
  • H.I. Assil et al.

    Crystal control in processed liquid honey

    Journal of Food Science

    (1991)
  • B. Bhandari et al.

    Rheology and crystallization kinetics of honey: present status

    International Journal of Food Properties

    (1999)
  • M. Bourne

    Food Texture and Viscosity: Concept and Measurement

    (2002)
  • C.M. Christensen

    Effects of taste quality and intensity on oral perception of viscosity

    Perception of Psychophysics

    (1980)
  • C.M. Christensen

    Oral perception of solution viscosity

    Journal of Texture Studies

    (1979)
  • C.M. Christensen et al.

    Oral and non-oral perception of solution viscosity

    Journal of Food Science

    (1987)
  • P.M. Falcone et al.

    Measuring rheological properties for applications in assessment of Traditional Balsamic Vinegar: description and preliminary evaluation of a model

    Journal of Food Engineering

    (2006)
  • P. Giudici

    Acido gluconico: criterio di genuinità dell’aceto balsamico tradizionale

    Industrie delle Bevande

    (1993)
  • P. Giudici et al.

    Cristallizzazione dell’Aceto Balsamico Tradizionale

    Industrie delle Bevande

    (2004)
  • Cited by (22)

    • Effect of sodium N-lauroylsarcosinate/hypromellose on the dispersibility and rheological behavior of carbon black for paper coating application

      2021, Progress in Organic Coatings
      Citation Excerpt :

      q-C curve was drawn to obtain the adsorption isotherm of CB dispersion. The rheological behavior of CB dispersion was determined by using cylinder rotary rheometer (Anton Paar, Austria) at 25 °C The shear-viscosity was recorded within shear rates ranging from 1 to 500 s−1 [22,23]. The dynamic viscoelasticity was measured as a function of angular frequency which was varied from 0.1 to 100 rad/s.

    • Evaluation of quality the pumpkin, wild plum, pear, cabbage traditional homemade vinegars using the spectroscopy and rheology methods

      2021, Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
      Citation Excerpt :

      Within this context, the main purpose of this study is to determine the quantitative and qualitative properties of traditional homemade vinegars made out of pumpkin, pear, wild plum (self-grown in high mountain regions without human intervention) and cabbage by analysing the presence and concentration of organic acids by using rheological measurements, UV and FT-IR spectroscopy techniques. For that purpose, initially UV spectroscopy and rheology measurements of widely known apple, grape and balsamic vinegars, were performed [3,27,28]. As the second step, UV spectroscopy, rheological analysis and Fourier-transform infrared spectroscopy of traditional homemade vinegars namely, pumpkin, wild plum, pear, and cabbage vinegars, are carried out.

    • Investigation of the traditional organic vinegars by UV–VIS spectroscopy and rheology techniques

      2021, Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
    • Simultaneous production of acetic and gluconic acids by a thermotolerant Acetobacter strain during acetous fermentation in a bioreactor

      2016, Journal of Bioscience and Bioengineering
      Citation Excerpt :

      Gluconic acid increases the biotechnological value of produced vinegar. Gluconic acid has been proposed as quality parameter of traditional balsamic vinegar because it contributes to the aromatic profile and viscosity of the vinegar (34,35). Acetic acid fermentation contributes to the vinegar aroma profile by converting some compounds present in fruit juices to aromatic compounds, such as gluconic acid and acetoin, which are obtained from glucose and dl-lactate, respectively (36).

    • Beyond traditional balsamic vinegar: Compositional and sensorial characteristics of industrial balsamic vinegars and regulatory requirements

      2015, Journal of Food Composition and Analysis
      Citation Excerpt :

      All of the samples fulfilled this minimum requirement. In Table 5, the viscosity values linked to mouthfeel sensation and flavor intensity (Falcone et al., 2008) seemed to be well correlated with density values (r = 0.89) and °Brix (r = 0.88) in line with literature (Chirife et al., 2009; Piva et al., 2008). New BVs were less viscous than the established ones indicating a more wine vinegar character but no particular comments were made by the assessors for this attribute.

    • Structure-composition relationships of the traditional balsamic vinegar of Modena close to jamming transition (part II): Threshold control parameters

      2012, Food Research International
      Citation Excerpt :

      The purpose of refilling is keeping in balance the three mass streams throughout the barrel set: the product loss by evaporation, the product withdrawn for the sale, and the leakages through the staves. Slow aging process should be allowed getting the authentic vinegar with the most appreciated rheological (Falcone, Verzelloni, Tagliazucchi, & Giudici, 2008) and sensorial properties (Giudici, Falcone, Scacco, & Lanza, 2009a; Giudici, Gullo, Solieri, & Falcone, 2009b). However, according to the law in force, titratable acidity (expressed as acetic acid equivalents) and density are the only two properties to be measured instrumentally and the commercial value of TBVM arises from the rank reached by sensory analysis that is usually performed by a panel of trained experts.

    View all citing articles on Scopus
    View full text