Food chemistry and biochemistry of enzymatic browning are reviewed with a focus on the author's research and recent information. Enzymatic browning is categorized into two types, immediate and delayed, according to the time required for browning. Apple browning has been extensively examined as an example of the former. The enzyme polyphenol oxidase (PPO) and its substrate polyphenols are separated into plastids and vacuoles, respectively, in cells. Disruption of this compartmentation by cutting, crushing, wounding, and physiological disorders allows interaction of the enzyme and substrate, and the reaction starts to turn brown. For the immediate type of enzymatic browning, regulation of oxidative polymerization of phenolic compounds by PPO is essential to inhibit browning. Browning of cut lettuce and mung bean sprouts are described here as the delayed type, in which phenylalanine ammonia-lyase (PAL) is induced during storage and phenolic compounds are synthesized de novo. The formed phenolic compounds are successively oxidized by PPO to turn brown. Regulation of PAL induction is crucial to inhibit this type of browning. Treatments with mild heat shock and cinnamaldehyde are described here as physical and chemical methods, respectively, to repress PAL induction and browning.
Polyphenols are commonly present in natural plants and serve as health benefiting food compounds. The health benefits and the metabolites of polyphenols have not yet been fully investigated because of lack of information about their bioavailability. This review was based on the previously reported literature focusing on the absorption and tissue accumulation of polyphenols. Furthermore, the physiological roles and the influx/efflux route(s) of non-absorbable polyphenols in the intestinal membrane were discussed.
In order to solve the problem of single aroma with rice wine brewed by uncooked material method, Zanthoxylum bungeanum, Glycyrrhiza uralensis Fisch, Osmanthus fragrans, glutinous rice and other materials were used to brew rice wine. Taking sensory evaluation and alcohol content as indexes, the suitable fermentation process parameters of compound rice wine with uncooked material method were determined by single factor test and response surface test. The results showed that when 1.7% Z. bungeanum seed, 1.0% G. uralensis Fisch, 3.0% O. fragrans and 1.5% koji were added to glutinous rice, the compound rice wine with 90.8 score of sensory evaluation and 9.1%vol alcohol content could be obtained by 18 days fermentation at 26.9 °C. The compound rice wine had bright yellow transparent, typical harmonious fruity aroma of the wine, mellow taste. The contents of limonene and linalool were 5.87 mg/L and 3.14 mg/L, respectively. Therefore, a theoretical basis for industrialized production was provided.
Fresh-cut lettuce is one of the most popular vegetables for healthy consumption. However, fresh-cut lettuce would spoil rapidly due to tissue damage. In order to improve the quality and extend the storage period of fresh-cut lettuce, this experiment investigated the effect of phytic acid (PA), vacuum packaging (VP), and combined treatment. The results showed that the PA + VP group inhibited the microbial growth and browning reaction of fresh-cut lettuce remarkably, and reduced the frangibility and the weight loss. The malondialdehyde (MDA), peroxidase (POD), and polyphenol oxidase (PPO) levels were decreased in PA + VP group. The combination of PA and VP can significantly inhibit the decline of total sugars, phenols, and vitamin C contents. Collectively, this study concluded that the combination of PA and VP was more effective in maintaining fresh-cut lettuce than alone treatment.
Fresh apples are easily damaged during machining processing. To solve the compression damage of the apple, the impacts of compression damage and storage time on failure mechanical behavior and quality indexes of apple fruits were evaluated in this study, where the different compression forces (0, 40, 80, 160, 320, 640 N) were loaded on the equator position of apple fruits stored at 5 ± 0.5 °C for 16 days. Then, we investigated the damaged mechanical behavior, damage volume, weight loss, ethylene production, respiratory rate, firmness, browning degree, titratable acidity (TA), total soluble solids (TSS), TSS/TA rate, malondialdehyde (MDA), cell membrane permeability, ascorbic acid, total phenolic, total flavonoids, pectin and soluble pectin of apple were analyzed. The experiment results showed that the apple fruit will not be damaged, if the compressive force is less than 40 N. Compared with the 0 and 40 N groups, the weight loss of harvested apple fruit under compressive forces with 80, 160, 320, and 640 N significantly increased, while the browning degree, MDA, cell membrane permeability and soluble pectin firmness, ascorbic acid, total phenolic, total flavonoids and pectin decreased. In conclusion, in the process of post-harvest processing (picking, transportation, sorting, and packaging), the contact force between apple fruit and mechanical equipment should be limited to less than 40 N to avoid mechanical damage, and thus extending its shelf life and improving its commercial quality.
Lanzhou lily has been confirmed as health care product and medicine because of its great ornamental and edible medicinal values. At present, the research on Lanzhou lily glycoprotein has not been reported in the literature. In this study, the glycoprotein components of Lanzhou lily were extracted and purified, and its structural characterization and immunological activity were studied. The results showed that Lanzhou lily glycoprotein (LGP-1) was linked by O-glycopeptide bonds and had characteristic absorption peaks of carbohydrate and protein. Moreover, LGP-1 possessed great immunological activity. When RAW264.7 was cultured for 48 hours with the glycoprotein concentration of 100 µg/mL, it could significantly promote cell proliferation and activate RAW264.7 to release NO and TNF-α. This confirms that LGP-1 has the potential to become a functional food.
We studied whether the preference for taste solutions affects swallowing in voluntary movements. The five basic tastes comprise sweetness and umami, which are preferred tastes, saltiness, which is preferred or not preferred depending on the concentration, and sourness and bitterness, which are repellent tastes. Taste palatability and ease of deglutition were set as objective variables, and 14 myoelectric potential factors were considered as explanatory variables and applied to partial least squares regression-variable importance in projection (PLS-VIP) analysis. For all tastes, highly accurate prediction formulas were obtained, but the important factors were different for each taste. The relationships between palatability/ease of deglutition and the myoelectric potential parameters were different for each taste modality.
Donkey meat is extremely popular in China owing to its high nutritional value and unique flavour. However, the physical and chemical properties of meat from the Dezhou black donkey have seldom been reported. This study aimed to compare differences in the physical characteristics, intramuscular fat (IMF) content, fatty acid profile, and antioxidant capacity of meat from Dezhou black donkey. The results showed that the L* and ΔE values of longissimus dorsi (LD) were significantly lower than those of gluteus maximus (GM) and biceps femoris (BF), while the b* value of LD was significantly higher than that of GM (p < 0.05). The shear force, hardness, adhesiveness, and elasticity values of LD and BF were significantly lower than those of GM (p < 0.05). The IMF content in LD was significantly higher than those in GM and BF (p < 0.05). The contents of fatty acids 15:0, 14:1, 18:2n-6, 20:4n-6, and polyunsaturated fatty acids in LD were significantly lower than those in GM and BF, while the 18:0, 18:1n-9, and monounsaturated fatty acid contents showed the opposite trend (p < 0.05). The superoxide dismutase activity of LD was significantly higher than those of GM and BF (p < 0.05), while the malonaldehyde content showed the opposite trend (p < 0.05). Overall, LD is an ideal edible part of Dezhou black donkey, owing to its higher IMF, tenderness, 18:1n-9, and antioxidant capacity levels, and lower 18:2n-6 and ΔE levels. This study provides novel insight into the development of donkey meat products.
Khanomjeen, a Thai fermented rice noodle, is made from fermented rice flour prepared from Indica rice that has traditionally undergone solid- and submerged-state fermentations. In response to changing consumer preferences, some khanomjeen producers have replaced the traditional solid-state fermentation with submerged fermentation, expecting a similar softness and whiteness to that of khanomjeen-style unfermented rice noodles. In the present study, the degree of protein removal in the modified fermentation method was lower than that of the traditional method. The hardness of khanomjeen made by the modified method was 60% of that made by the traditional method but its whiteness was identical to that of the unfermented rice noodles. The metagenomic profiles revealed that the modified method allowed the growth of possibly proteolytic bacteria, but suppressed possibly pigment-producing bacteria. The modified fermentation method could thus help to control the microbiota to improve the texture and color of khanomjeen and meet current consumer demands.
Fructose is widely used in food and beverage industries as a sweetener. In this study, solubility data of fructose in aqueous ethanol (50, 60, 70, 80, and 90% w/w) at 25, 35, and 45 °C were experimentally investigated. With the increase in the ethanol concentration the solubility decreased while with the increase in temperature the solubility increased. Dissolution enthalpy was determined according to the van't Hoff plot. It was found that the enthalpy linearly increased with the ethanol concentration. Additionally, an empirical solubility model was developed to estimate fructose solubility and validated with literature data. The model gave different root mean square errors (RMSE) for different sets of literature data, but overall, the model can estimate the solubility of fructose (mass fraction) with relatively high accuracy with RMSE of 0.056.