Determination of the Sugar Content in Commercial Plant Milks by Near Infrared Spectroscopy and Luff-Schoorl Total Glucos
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Determination of the Sugar Content in Commercial Plant Milks by Near Infrared Spectroscopy and Luff-Schoorl Total Glucose Titration Giorgio Marrubini 1 & Adele Papetti 1
&
Emiliano Genorini 2 & Alessandro Ulrici 3
Received: 10 June 2016 / Accepted: 7 November 2016 / Published online: 15 November 2016 # Springer Science+Business Media New York 2016
Abstract Thirty-nine samples of plant milks (rice, soy, oat, barley, spelt, quinoa, almond, and a variety of wheat called kamut) were analyzed for their reducing sugars content by NIR spectroscopy, using the Luff-Schoorl official method as reference to build the calibration models. The amount of reducing sugars, expressed as grams of glucose/100 mL of beverage, ranged from 0.5 g/100 mL (soy) to 7.6 g/100 mL (rice). Both partial least squares (PLS) and interval-partial least squares regression (iPLS) were used to build multivariate calibration models, testing different spectra preprocessing methods. The performance in prediction of the best calibration model was evaluated on an external test set of nine randomly selected samples (RMSEP = 0.98 g/100 mL, R2PRED = 0.84), and its statistical significance was assessed using a randomization t test based on Monte Carlo simulations. The results obtained suggest that NIR spectroscopy can be a valid alternative to the laborious reference titrimetric method for the determination of total glucose content in plant milks.
Keywords Plant milk . Glucose determination . Luff-Schoorl method . NIR spectroscopy . Variable selection . Randomization test
* Adele Papetti [email protected]
1
Department of Drug Sciences, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
2
Bruker Italia S.r.l, Viale V. Lancetti 43, 20158 Milan, Italy
3
Department of Life Sciences, University of Modena and Reggio Emilia, padiglione Besta, via Amendola 2, 42122 Reggio Emilia, Italy
Introduction In recent years, the food market in industrialized countries offered a number of products presented as healthier than the traditional ones consumed for many decades (Kearney 2010). This has become especially evident for milk which is often compared for its nutritional properties to non-dairy products derived from vegetables, often referred to as plant milks. Many products, such as cheese-like foods of vegetable origin (e.g., tofu), are also proposed as healthier, balanced, low-fat, and low-calories substitutes of dairy products. Plant milks and dairy-like products are free of lactose and animal proteins and are thus proposed as suitable foods for lactose-intolerant and allergic patients and for vegetarians (Bernat et al. 2014). On the Italian market, the more represented plant milks are those produced using almond, millet, rice, soy, oat, barley, and a variety of wheat called kamut. Plant milks are obtained by extraction with hot water and filtration from the starting raw material which is processed depending on the nature of the crop (e.g., nut or cereal). Common pretreatments include one or more steps like washing, grinding, blanching, and also peel
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