Free Amino Acids and Volatile Aroma Compounds in Watermelon Rind, Flesh, and Three Rind-Flesh Juices.

Watermelon rind is treated as agricultural waste, causing biomass loss and environmental issues. This study aimed to identify free amino acids and volatiles in watermelon rind, flesh, and rind-flesh juice blends with ratios of 10%, 20%, and 30%. Among the 16 free amino acids quantified, watermelon rind alone contained higher total amino acids (165 mg/100 g fresh weight) compared to flesh alone (146 mg/100 g). The rind had significantly higher (1.5×) and dominant amounts of citrulline and arginine (61.4 and 53.8 mg/100 g, respectively) than flesh. The rind, however, contained significantly lower amounts of essential amino acids. Volatile analysis showed that watermelon rind total volatiles (peak area) comprised only 15% of the flesh volatiles. Of the 126 volatiles identified, the rind alone contained 77 compounds; 56 of these presented in all five samples. Aldehydes and alcohols were most prevalent, accounting for >80% of the total volatiles in all samples. Nine-carbon aldehyde and alcohol compounds dominated both the flesh and rind, though the rind lacked the diversity of other aldehydes, alcohols, ketones, terpenes, terpenoids, esters and lactones that were more abundant in the watermelon flesh. Watermelon rind was characterized by the major aroma compounds above their thresholds, including 17 aldehydes and six unsaturated nine-carbon alcohols. This study demonstrated the potential for rind as a food or beverage supplement due to its key features such as concentrated citrulline and arginine, relatively low odor intensity, and valuable volatiles associated with fresh, green, cucumber-like aromas.

Using texture analyzer to characterize pecan and olive oil tactile properties, compare to viscometer analysis, and link to fatty acid profile and total polyphenols.

This study aimed to characterize mechanical properties of five pecan oils and one olive oil using a texture analyzer compared to a rotational viscometer; the results were linked to fatty acid profile and total polyphenol content. The seven texture parameters (firmness, consistency, cohesiveness, viscosity index, and stickiness at 5 s, stickiness at 30 s, and delta stickiness) showed significant difference (p ≤.05) among the six oils. Overall, olive oil had higher texture analysis values and significantly higher rotational viscosity than pecan oils. Chemically, C18 fatty acids accounted for approximately 90% of the total fatty acids in the five pecan oils. Olive oil had a higher amount of long-chain, unsaturated fatty acids. Total polyphenols in pecan oils were 8-15 mg gallic acid equivalent (GAE)/100 g, while olive oil contained 27.2 mg GAE/100 g. Correlation analysis demonstrated a significant, positive relationship between "consistency" texture and rotational viscosity measurement. Mechanical properties (seven texture parameters and rotational viscosity) were partially correlated to fatty acid profile, though no universal pattern was identified.