Chemometric analysis of minerals in gluten-free products.

BACKGROUND: Numerous studies indicate mineral deficiencies in people on a gluten-free (GF) diet. These deficiencies may indicate that GF products are a less valuable source of minerals than gluten-containing products. In the study, the nutritional quality of 50 GF products is discussed taking into account the nutritional requirements for minerals expressed as percentage of recommended daily allowance (%RDA) or percentage of adequate intake (%AI) for a model celiac patient. Elements analyzed were calcium, potassium, magnesium, sodium, copper, iron, manganese, and zinc. Analysis of %RDA or %AI was performed using principal component analysis (PCA) and hierarchical cluster analysis (HCA). RESULTS: Using PCA, the differentiation between products based on rice, corn, potato, GF wheat starch and based on buckwheat, chickpea, millet, oats, amaranth, teff, quinoa, chestnut, and acorn was possible. In the HCA, four clusters were created. The main criterion determining the adherence of the sample to the cluster was the content of all minerals included to HCA (K, Mg, Cu, Fe, Mn); however, only the Mn content differentiated four formed groups. CONCLUSION: GF products made of buckwheat, chickpea, millet, oats, amaranth, teff, quinoa, chestnut, and acorn are better source of minerals than based on other GF raw materials, what was confirmed by PCA and HCA. © 2017 Society of Chemical Industry.

Green tea extract as an anti-browning agent for cloudy apple juice.

BACKGROUND: Enzymatic browning of fruits and vegetables and their products is an important factor worsening their quality. The influence of five green tea extracts at the concentrations of 1 g L-1 , 2 g L-1 and 3 g L-1 on polyphenol oxidase (PPO) activity in fresh cloudy apple juice was investigated. Moreover, PPO inhibition by tea extract and colour stability of juice during short-time refrigerated storage was studied. The changes of juice colour during storage was expressed as the total colour differences (ΔE*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A420 ). RESULTS: All extracts inhibited PPO activity in fresh apple juice in concentration-dependent manner. PPO activity in pure apple juice decreased by 7% after 48 h, whereas PPO activity in samples with 1 g L-1 , 2 g L-1 and 3 g L-1 tea extract decreased by 53%, 74%, and 96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48 h, extract at 1 g L-1 , 2 g L-1 and 3 g L-1 inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice. CONCLUSION: Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices. © 2016 Society of Chemical Industry.