Almond hull, a substantial byproduct comprising more than half of almond fresh weight, has recently gained attention due to its functionality and sustainability benefits. Despite heightened interest, information regarding its toxicity remains limited. In order to assess its genotoxic potential, we conducted Good Laboratory Practice-compliant in vitro and in vivo studies following Organization for Economic Co-operation and Development (OECD) guidelines. No evidence of toxicity or mutagenicity was observed in a bacterial reverse mutation assay using five tester strains, evaluating almond hull at concentrations up to 5 mg/plate, with or without metabolic activation. Almond hull did not induce chromosome structural damage in a chromosome aberration assay using Chinese hamster ovary cells, nor did it cause any spermatogonial chromosomal aberration in tested male BALB/c mice. To evaluate its ability to induce DNA damage in rodents, a combined micronucleus assay was conducted in KM mice of both sexes. Almond hull was administered at doses of 1250, 2500, and 5000 mg/kg/day via gavage once daily for 2 days. No adverse effects of almond hull were observed in the micronucleus assay. Our results indicate no evidence of the genotoxic potential of almond hull administered up to the maximum concentrations of 5 g/kg, as recommended by OECD guidelines.

Almond hull, a substantial byproduct constituting more than half of almond fresh weight, has garnered recent attention due to its abundance in fiber and bioactive content. Despite this huge interest, data on its toxicity remain scarce. In line with the Organization for Economic Cooperation and Development (OECD) 423 guidelines, this study conducted an acute oral toxicity test using almond hull powders processed from three major almond varieties of Butte, Monterey, and Nonpareil on BALB/c female mice, administering dosages of 300 mg/kg body weight (bw), 2000 mg/kg bw, and 5000 mg/kg bw, with observations over a 14-day period. The results indicated that almond hull powders were non-toxic, aligning with the Globally Harmonized System\'s classification. Administering up to 5000 mg/kg bw of all three varieties of almond hull powders (female BALB/c mice) and 10,000 mg/kg bw of Monterey almond hull powders (both female and male mice) induced no adverse effects in terms of mortality, body weight changes, food intake, organ to weight ratio, and clinical biochemistry. Additionally, histopathological examination revealed no organ abnormalities. This study demonstrates the non-toxic nature of almond hull as an edible food ingredient under experimental conditions, encouraging the further exploration of its potential for safe consumption and its health benefits.

Hulls are the principal almond by-products and are rich in bioactive compounds, such as polyphenols and fibre. Generally, hulls are used as animal feed; however, because of their valuable chemical composition, alternative applications as a natural food ingredient and dietary supplement should be evaluated. The aim of this study was to assess the physico-chemical and nutritional characteristics and the consumer acceptability of bread produced by replacing 4% and 8% of wheat flour with almond hulls (AHs) obtained from six almond varieties at two ripening stages (green and mature). The use of AHs in bread production increased fibre content, polyphenol content, and antioxidant activity. In particular, bread containing mature AHs showed the highest quantities of fibre and sugars, mainly glucose, whereas bread containing green AHs showed the highest polyphenol content. The polyphenol content and antioxidant activity in bread containing green AHs were 272.88 mg GAE/100 g dry weight and 1145.32 μmol TE/100 g dry weight, respectively, of which 60.5% and 52% were bioaccessible after in vitro digestion. Bread containing AH powder showed slightly lower specific volume, darker crumb colour, and lower hardness than those of the control. Consumer evaluation indicated that breads with 8% AH powder were those with the most overall liking.

The objective of this study was to evaluate 2 varieties of almond hulls (prime and California type hulls) as an alternative feed ingredient on the performance, egg quality, nutrient digestibility, and body composition using a total of 100 23-week-old Hy-Line W36 hens. Treatments consisted of a control diet based on corn and soybean meal; T2 and T3 were formulated to contain 7.5 and 15% of prime hulls; and T4 and T5 contained 7.5 and 15% of California type hulls. Inclusion of prime hulls and California type hulls had no effects on feed intake, egg laying rate, and feed conversion ratio, but California type hulls at 7.5% decreased (P < 0.001) body weight gain compared to the control. Prime hulls at 7.5% and California type hulls at both levels improved (P ≤ 0.022) AMEn and N digestibility. Both prime hulls and California type hulls had no effects on egg size, specific gravity, Haugh unit, and percentages of yolk, albumen and shell, but yolk color appeared greener and less yellow (P ≤ 0.009) by prime hulls and less yellow (P = 0.001) by California type hulls. For body composition, prime hulls and California type hulls at both levels lowered (P ≤ 0.017) body fat, and California type hulls at 7.5% decreased (P = 0.001) lean weight. In summary, inclusion of prime hulls and California type hulls up to 15% had no negative effect on egg production and egg quality while reduced the body fat percentage and mass.

In humans, the consumption of soluble fibers reduces glycemic response after a meal. We hypothesized high soluble fiber diets would reduce and delay postprandial glucose and insulin responses in horses. In a 4 × 4 Latin square design experiment, four Quarter Horse geldings were adapted to diets containing orchardgrass hay (ORCH) or ORCH with 1 of 3 treatment ingredients: molassed sugar beet pulp (BEET), almond hulls (HULL), or steam-crimped oats (OATS). Blood was serially sampled for 6 hours after feeding 0.15% body weight (BW) of the treatment ingredient (meal test) or 1.1 g starch/kg BW from oats plus the treatment ingredient (starch test) to evaluate glycemic and insulinemic responses. Glycemic response during the meal test peaked between 60 and 90 min after feeding (P < .05) and tended to be altered by diet (P = .071) and diet × time (P = .076). Serum insulin was affected by diet (P = .008), time (P < .001), and diet × time (P < .001) during the meal test, with concentrations lower in ORCH compared with BEET and OATS (P < .05). In the starch test, glucose was lower (P < .05) in ORCH and HULL compared with BEET and insulin was lower (P = .046) in ORCH compared with BEET. In both tests, horses took longer (P < .05) to consume HULL, likely influencing postprandial responses. Future research integrating the functional properties of feeds with physiological responses will be necessary to elucidate how soluble fiber affects postprandial glucose metabolism in horses.

Ultrasound-assisted extraction (UAE) was applied as a pretreatment technique to improve the recovery of polyphenols from the almond hulls of four Tunisian and three Italian almond varieties, followed by the characterization with HPLC-DAD. The operating parameters (solid/liquid ratio, extraction time, and ethanol concentrations) were optimized using a Response Surface Methodology. A polynomial equation was calculated to describe the relationship between the operating parameters and dependent variables as total polyphenolic content (TPC) and antioxidant activity (RSA). A desirability function approach was used to determine the optimum conditions for operating parameters: a solid:solvent ratio of 2 g/100 mL, an extraction time of 13 min, and an ethanol concentration of 51.2%. Among the almond varieties, Pizzuta and Fakhfekh showed the highest polyphenol content and antioxidant activity. HPLC-DAD analysis of almond hull extracts confirmed that chlorogenic acid, catechin, and protocatechuic acid were the most important polyphenols in almond hull. The results highlighted that UAE could be an effective technique for the recovery of phenolic compounds from almond hull, thereby making this byproduct a promising source of compounds with potential applications in food and healthcare sectors.

Several studies have revealed that among foods, the consumption of edible nuts has beneficial effects on health which are attributed to their high content of potent antioxidants. Among nuts, the whole seed of the almond (Prunus dulcis) has been demonstrated to possess potent free radical scavenging activity, which is related to the presence of phenolic compounds. The aim of the current study is to evaluate the polyphenol content and the antioxidant ability of almond hull, which is an agriculture solid waste. The present results revealed that among different extraction methods, the acetone extract of almond hulls has a high content of phenolic and flavonoid compounds and a high antioxidant ability, which were determined by using the phosphomolybdenum method and by measuring the potency of the antioxidant, respectively. Moreover, the experimental data disclosed that the acetone extract of almond hulls provides protection against the oxidative damage and the membrane protein degradation that are caused in human erythrocytes by hydrogen peroxide. These phenomena may likely be due to the recruitment of antioxidants by cell membranes and/or translocation to cytosol. Overall, almond hull extract could be considered as a natural source of antioxidants, and its consumption could have a positive effect on human health.