Archaeological dental calculus has emerged as a rich source of ancient biomolecules, including proteins. Previous analyses of proteins extracted from ancient dental calculus revealed the presence of the dietary milk protein β-lactoglobulin, providing direct evidence of dairy consumption in the archaeological record. However, the potential for calculus to preserve other food-related proteins has not yet been systematically explored. Here we analyse shotgun metaproteomic data from 100 archaeological dental calculus samples ranging from the Iron Age to the post-medieval period (eighth century BC to nineteenth century AD) in England, as well as 14 dental calculus samples from contemporary dental patients and recently deceased individuals, to characterize the range and extent of dietary proteins preserved in dental calculus. In addition to milk proteins, we detect proteomic evidence of foodstuffs such as cereals and plant products, as well as the digestive enzyme salivary amylase. We discuss the importance of optimized protein extraction methods, data analysis approaches and authentication strategies in the identification of dietary proteins from archaeological dental calculus. This study demonstrates that proteomic approaches can robustly identify foodstuffs in the archaeological record that are typically under-represented due to their poor macroscopic preservation.

Phytoliths and biomolecular components extracted from ancient plant remains from Chang’an (Xi’an, the city where the Silk Road begins) and Ngari (Ali) in western Tibet, China, show that the tea was grown 2100 years ago to cater for the drinking habits of the Western Han Dynasty (207BCE-9CE), and then carried toward central Asia by ca.200CE, several hundred years earlier than previously recorded. The earliest physical evidence of tea from both the Chang’an and Ngari regions suggests that a branch of the Silk Road across the Tibetan Plateau, was established by the second to third century CE.

Mortars are the layers paved on the surface of timber, earth or stone before painting and drawing. The analysis of their material composition and manufacture technology is necessary for revealing old technological approaches, selecting a suitable technological process in restoration and protection, and guiding the development of traditional technology of Chinese painting and colored drawings. According to ancient literature, crop flour and blood have been used as binders in the mortars of Chinese wooden buildings. However, little work is published on their scientific identification, and the reported methods could not determine their precise origins, which is important to understanding ancient mortar technology. In this study, Fourier Transform Infrared Spectroscopy (FTIR), Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS) and starch grain analysis were employed to analyze the three mortars taken from the Old Summer Palace (18th and early 19th centuries), the Eastern Royal Tombs of the Qing Dynasty (middle 17th to early 20th centuries) and the Taiyuan Confucius Temple (late 19th century), respectively. FTIR analysis indicated the presence of proteins, and then different organic additives, namely, wheaten flour, cattle blood and pig blood, were identified respectively in the three mortars by LC/MS/MS analysis. Starch grain analysis also confirmed the proteomic results. Thus, proteomic analysis is highly effective for identifying the nature and origin of organic additives in the mortars of ancient painting.